Home

Data User Guide

1. J J Parrish A and Remsberg E E Ground based microwave observations of ozone in the upper stratosphere and mesosphere J Geophys Res 99 D8 16 757 16 770 1994 Eskes H J and Boersma K F Averaging kernels for DOAS total column satellite retrievals Atmos Chem Phys 3 1285 1291 2003 Frie U Monks P S Remedios J J Rozanov A Sinreich R Wagner T and Platt U MAX DOAS O measurements A new technique to derive information on atmospheric aerosols 2 Modeling studies J Geophys Res 111 D14203 doi 10 1029 2005JD006618 2006 Rodgers C D Inverse Methods for Atmospheric Sounding Theory and Practice World Scientific Publishing Singapore NewJersey London Hong Kong 2000 III Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 Ozone Microwave Radiometry A Intro general A 1 Instrument fiche Table 5 Ozone Microwave Radiometry instrument fiche Platform ground based Measuring technique passive pressure broadened emission line Observation geometry uplooking typically 20 40 elevation Units Volume mixing ratio vmr Vertical resolution 10 20 km increasing with altitude Horizontal resolution Field of view typically 6 degree Temporal resolution 30 min 60 min integration of 20 sec line spectra Vertical range 20 70 km Horizontal range about 5x5km at 50 k
2. measurement Additional products Temperature profile retrieved from the off wavelength signal Future potential Aerosol backscatter profile Caveats The lower limit and upper limit of the ozone profile depend on the laser power and the meteorological conditions B Operation mode The lidar is a remote sensing instrument Depending on the desired measurement lidar systems use various light matter interactions such as Rayleigh Mie and Raman scattering or fluorescence Measurements of atmospheric ozone temperature or aerosol are based on the first 3 processes Generally a lidar measurement consists in sending into the atmosphere a laser beam a small part of this laser radiation is scattered back to the ground where it is collected by a telescope detected by a photomultiplier tube and analysed by an electronic acquisition system Range resolved measurements can be obtained using pulsed lasers In order to measure the ozone vertical distribution the Differential Absorption Laser technique DIAL is used This technique requires the simultaneous emission of two laser beams characterised by a different ozone absorption cross section A lidar system includes basically one or several laser sources with optical devices to reduce the divergence of the beam a telescope which collects the light scattered back by the atmosphere an optical analysing system with detectors such as photomultipliers to detect the optica
3. to be considered is the sun and in the infrared one can omit scattering and therefore the extinction coefficient reduces to the absorption coefficient aps The equation can be re written as IL Du exp f daps v s P T x s ds 2 in which x s is the absorber s concentration at position s along the line of sight The equation is written in the case of one single absorber in practice of course the extinction factors due to every single absorber must be multiplied The inversion of this equation enables therefore the determination of the absorbers concentrations assuming perfect knowledge of the light path trajectory and of the absorption coefficients and their dependence on P and T In practice the solution of the equation is not unequivocal ill posed problem and some a priori knowledge must be used to find the most probable solution The methods most often used at present are the Optimal Estimation Method and Tikhonov regularization Rodgers 2000 The mathematics are shortly summarized in ISSI 2012 The inversion then yields the retrieved vertical distribution x along the vertical z of the target absorber s in the atmosphere Xr Z Xa A X Xa 3 in which x and x are the a priori and true vertical profiles of the target absorber respectively and A is a product of the retrieval process the so called Averaging Kernel a square matrix E L2 data and use caveats The L2 data consist o
4. 1007 978 1 4614 3909 7 2012 ISBN 978 1 4614 3908 0 2013 Rodgers C D Inverse methods for atmospheric sounding Series on Oceanic and planetary physics vol 2 World Scientific 2000 II Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 DOAS MAXDOAS A Instrument fiche Table 4 DOAS MAXDOAS instrument fiche Instrument Multi AXis Differential Optical Absorption Spectrometer MAX DOAS Platform ground based Measuring technique Solar light absorption spectrometry Observation geometry Looking at scattered light from the zenith and various directions above the horizon Some instruments also perform direct sun observations Units Total columns mol cm2 and volume mixing ratio per atmospheric layer vmr and partial column per atmospheric layer mol cm2 Vertical resolution Strongly varying from 100 m close to the ground to column above 5 km Horizontal resolution Depending on solar zenith angle of measurement vertical layer position and wavelength range used and atmospheric aerosol load and vertical profile of the target species the horizontal resolution decreases as the SZA increases and if the target gas is located higher in the atmosphere In the boundary layer it decreases with increasing aerosol load and towards shorter retrieval wavelengths Temporal resolution Better than 1 minute for tropospheric colum
5. 20 Mode of Operation Total power Temperature of Mixer 60K System noise temperature 1200 K Frequency 142 175 GHz Target species O3 aux Quantities Water vapour column Altitude Range of target species 30 75 km Time resolution 60 min B 2 b Operation mode OZORAM measures semi automatically The operator checks the instrumental features and fills in a protocol every day Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 o twor ound e GMES The OZORAM operates in Total Power mode i e a hot H ambient temperature and a cold load C 60 K cryogenically cooled along with the mixer measured alternatively with the sky A in a ratio H A C 50 44 6 in order to produce the highest signal to noise ratio at a sky temperature of about 80K The cold load is a cryogenically cooled black body which is calibrated checked once a week using a black body cooled with liquid nitrogen The raw data called LO are transferred to the University of Bremen where they are stored along with all data necessary to calibrate the spectra and secured on a dedicated computer system The granularity of the raw data is about 10 min which is also the highest time resolution the OZORAM measurements could have in the current setup B 2 c L1 data The L1 data are the frequency and power calibrated spectra The calibration is performed offline as well as the retrieval The L1
6. E Ile de La R union on 25 1 2011 04 04 UT for a solar zenith angle of 62 and an azimuth angle of 101 measured from N 0 to E 90 The Table provides the geographical location of the points along the line of sight corresponding to a percentage of the total CH4 column Latitude Longitude Altitude km Distance from Percentage North East instrument location km 0 20 900 55 480 0 05 0 0 20 20 906 55 511 1 8 3 3 40 20 912 55 546 3 8 7 0 60 20 921 55 596 6 6 12 3 80 20 934 55 666 10 6 19 7 Table 3 Example of a ray tracing output for O3 providing the geographical location of the points along the line of sight corresponding to a percentage of the total O3 column measurement on 25 1 2011 4 04 UT with solar zenith angle 62 and azimuth angle 101 measured from N 0 to E 90 Percentage Latitude North Longitude East Altitude km Distance from instrument location km 0 20 900 55 480 0 1 0 0 20 20 947 55 740 14 8 27 5 40 20 963 55 827 19 8 36 8 60 20 975 55 893 23 6 43 8 80 20 991 55 980 28 6 53 0 G References ISSI 2012 Schneider Matthias Philippe Demoulin Ralf Sussmann and Justus Notholt Fourier Transform Infrared Spectrometry Chapter 6 in Monitoring Atmospheric Water Vapour Ground Based Remote Sensing and In situ Methods ISSI Scientific Report Series Vol No 10 Editor Niklaus K mpfer Springer DOI 10
7. Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 A 2 Measurement technique Ozone microwave radiometers are operated indoors The microwave radiation of the atmosphere passes through the blue styrofoam window Figure 15 A typical ozone microwave radiometer GROMOS at Bern Figure 15 shows a typical ozone microwave radiometer GROMOS at Bern The brightness temperature of the atmosphere is calibrated by means of a cold load A vessel with liquid nitrogen provides a black body brightness temperature of 80 K A FFT spectrometer records the pressure broadened ozone line spectra at 142 GHz with a bandwidth of 1 GHz Figure 16 Frontend with quasi optics of the microwave radiometer Figure 16 shows a frontend with quasi optics of the microwave radiometer Rotating aluminum plate mirror left hand side Martin Puplett Interferometer with wire grids and corner mirrors middle a copper horn antenna wave guides and mixers right hand side Title Data User Guide n S Deliverable number D 4 2 letworl Ground Based Obse the GMES Atmosph Revision 00 Status Final Date of issue 08 05 2013 Electromagnetic Electromagnetic radiation from slant radiation from cold atmosphere column elevation angle load liquid nitrogen for sky measurement is 40 T 80K T 40 260 K Electromagnetic radiation from hot load temperature stabilized
8. aerosol vertical profiles is based on the fact that the concentration of O is proportional to the concentration of O2 Therefore variations in O can be related to changes in aerosol abundance A simultaneous use of O measurements at several wavelengths can significantly increase the information content During clear sky conditions the intensity observed in off axis geometry relative to the zenith measurement can be additionally used as input for the retrieval 04 477nm 04 4wl 04 4wl INT LA Altitude km Altitude km Altitude km K Ob ra reer ere SECUN Fo Saray Or 1a a a E a aa La ea Seren 0 E ESPRIT n D 0 00 0 02 0 04 006 0 08 G10 O12 0 00 0 02 G04 0 06 0 08 9 10 O12 0 00 0 02 G04 0 06 0 08 G10 O12 Extinction 477nm 1 km Extinction 511nm 1 km Extinction 511nm 1 km a b c 04 477nm D4 4wl 04 4wl INT Alt km Alt km Alt km 4 af E d E qi l DA 0 3 0 3 6 5 6 5 6 5 0 7 0 7 0 7 Ht H T 3 F lp H E 15 1B 15 D I 1 og 1 og ig 3 21 3 21 3 EN E 25 23 6 2 5 T 25 lt 250 2 5 1 27 4 27 1 ET 2 9 2 9 2 9 3 1 d 3 1 3 3 3 3 3 3 d 3 5 30 V 3 5 GL 7 abaa Ge D ran bout 1 Chi rasan La uad 0 2 Q0 02 04 9 6 z 1 0 0 4 0 2 DD 02 04 D 08 1 0 0 4 0 2 DD 02 04 D 08 1 0 Extinction averaging kernel a u Extinction averaging kernel a u Extinction averaging kernel a u d e f Figure 11 Example for retrievals top and averaging kernels bottom
9. are indicative of strong pollution in the boundary layer E L2 data and use caveats including concept examples of horizontal vertical averaging Vertical averaging When comparing MAX DOAS trace gas and aerosol vertical profiles to correlative data e g model satellite or FTIR the difference in vertical resolution between both data sets must be taken into account Since the MAX DOAS profiles generally display the lowest vertical resolution the correlative data should be degraded to the MAX DOAS resolution in order to avoid apparent biases at altitudes where one measurement has no or little sensitivity For an Optimal Estimation based MAX DOAS retrieval this is done by convolving the correlative profiles with the coincident MAX DOAS averaging kernels AVK using the following expression Connor et al 1994 Xer X A X RW Xa where A is the MAX DOAS averaging kernel matrix x is the a priori profile used in the MAX DOAS retrieval x is the correlative high resolution profile and x i is the smoothed or convolved correlative profile The averaging kernels which are the rows of the A matrix express the sensitivity of the retrieved profile with respect to the true atmospheric profile Rodgers 2000 Ideally each averaging kernel should be a single discrete peak at its corresponding altitude In practice the information retrieved at a given altitude is also influenced by the nearby layers and hence the averaging kernels are pe
10. data is calculated using the total power formula and the measured temperatures of the hot and cold black body B 2 d L1 gt L2 data The calibrated L1 spectra are integrated further to reach a time resolution of 60 minutes This time resolution is a compromise between a high time resolution and a signal to noise ratio sufficient to retrieve a profile up to the physical limit at about 75 km altitude The physical limit is defined by the properties of the radiation at this frequency in this viewing geometry and cannot be raised The retrieval uses the ARTS QPACK software package which is dedicated to measurements in the millimeter wave region QPACK is an implementation of the optimal estimation method to invert ill posed functions There is no tropospheric correction i e contrary to most instruments the tropospheric contribution is not estimated and removed from the measured spectrum The tropospheric absorption is fitted along with the O profile Because the OZORAM is affected by wavelike structures on the spectrum the retrieval also fits a number of standing waves along with the profile This is the reason while the lower boundary of the altitude range is 30 km not below 20 km as theory would predict The noise on the spectrum is calculated using the system noise temperature and used as a fit parameter The a priori profile and the auto covariance matrix are fixed Title Data User Guide Deliverable number D 4 2 NO R S Revisio
11. of the aerosol extinction profile based on synthetic measurements Figure 11 a d Retrieval using only O at 477 nm b e combined retrieval with O at 360 477 577 and 630 nm c f combined retrieval with O and relative intensity at 360 477 577 and 630 nm The upper panels show the true black a priori dotted red and retrieved solid red profiles as well as the true profile convolved with the averaging kernel green Figure 12 shows retrieved aerosol extinction profiles together with the corresponding averaging kernels for retrievals using only a single O absorption band multiple O absorption bands as well as simultaneously multiple O4 absorption bands and relative intensity The colour code of the averaging kernels indicates the retrieval altitude Each of these curves quantifies the sensitivity of the retrieved profile at given altitude to the true profile providing a measure for the sensitivity and vertical resolution In this example the sensitivity of the retrieval is restricted to the lowermost 2 km of the atmosphere but the sensitivity for the 2 3 km range improves significantly if several wavelengths and or the relative intensity are considered in the retrieval It is important to note that owing to the non linear nature of the inverse problem the vertical resolution and information content of the aerosol retrieval strongly depend on the aerosol extinction profile Title Data User Guide Deliverable number D 4 2 O
12. 2013 Figure 1 shows an experimental setup Top left meteostation top right suntracker bottom Fourier transform spectrometer The meteo station includes a Vaisala wind humidity rain detector in the red circle a sunshine detector total solar irradiance in the green circle a high precision barometer in the orange circle and a presence of rain detector in the yellow circle Title Data User Guide Deliverable number D 4 2 hr Revision 00 Status Final SE Date of issue 08 05 2013 The solar lunar light is guided into the spectrometer by a precise suntracker that follows the sun during the day The system has an active feedback system in order to keep the sun image at all times centered on the entrance aperture of the spectrometer The alignment of the solar beam in the spectrometer is critical and is verified regularly with a cell measurement the measurement with high spectral resolution of order 0 003 cm 1 of the absorption spectrum of a known gas eg HBr N20 CS2 with a known concentration at low pressure in the cell reveals the instrument line shape and permits verification of the alignment The spectrometer is equipped with an InSb detector covering the range 1 to 5 um and a HgCdTe detector covering the range 1 5 to 16 um Both detectors are cooled to liquid N temperatures The recorded signal LO is an interferogram which is then transformed via a Fast Fourier Transform FFT algorithm into a spectrum L1 da
13. 5 500 525 550 575 Wavelength nm Figure 7 Example of two spectra taken during the CINDI campaign in Cabauw Figure 7 is an example of two spectra Iv1 taken during the CINDI campaign in Cabauw 51 96 N 4 9 E on July 1 2009 around noon The blue spectrum was taken in zenith direction while the red spectrum was measured at an elevation of 1 above the horizon The spectra are dominated by Fraunhofer lines The difference in slope is the result of scattering zenith is bluer than the horizon C L1 data L1 data are spectra of intensity as a function of wavelength Before use in the inversion the dark signal of the detector is subtracted data screening for too low noisy or too high saturated signals is performed and a preliminary wavelength axis is assigned to the data Additional information such as location time of measurement solar zenith and azimuth angle the observation geometry and instrument settings is attached to the spectra Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 D L1 gt L2 data processing principles Data analysis is divided into two steps 1 Determination of atmospheric column amounts integrated along the light path slant column densities SCDs by application of the Differential Optical Absorption Spectroscopy method 2 Conversion to vertical column densities VCs or vertical profiles The DOAS fit is based on a linear least square solution
14. For the non absorbed wavelength different techniques are used mainly the generation of a wavelength at 353 nm corresponding to the first Stokes radiation by stimulated Raman effect in a cell filled with hydrogen Werner et al 1983 the use of the third harmonic of a Nd Yag laser 355 nm Godin et al 1989 or the use of a XeF laser which provides a wavelength at 351 nm Nakane et al 1994 Lidar measurements are performed during nighttime and require clear sky meteorological conditions laser radiation is rapidly absorbed by clouds and only cirrus can be tolerated for accurate stratospheric measurements The DIAL algorithm follows basically the theoretical derivation of the ozone number density from the lidar signals The main steps are the following e Temporal signal averaging e Correction from Y background light v dead time correction in the case of photon counting acquisition due to the saturation of the photon counting systems with high intensities e Derivation of the ozone number density from the corrected lidar signals C L1 data In the routine mode the lidar signals are time averaged over the whole measurement period 3 4 h in general in order to increase the signal to noise ratio cf figure 21 Raw signals 0 High Low 308 nm 308 nm 355nm 355 nm Raman channels Ke 332 nm 387 nm Normalized counts photons pulse 80 100 120 140 Altitude km Figure 21 Temporal signal averagi
15. Title Data User Guide Deliverable number D 4 2 f O R S Revision 00 Status Final IDE Date of issue 08 05 2013 ORS Network of Remote Sensing Ground Based Observations in support of the Copernicus Atmospheric Service Data User Guide Deliverable title Data User Guide Deliverable number D4 2 Revision 00 Status Final Planned delivery date 30 04 2013 Date of issue 08 05 2013 Nature of deliverable Report Lead partner BIRA IASB Dissemination level Public This work has received research funding from the European Community s Seventh Framework Programme FP7 2007 2013 under grant agreement n 284421 SEVENTH FRAMEWORK PROGRAMME Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 DOCUMENT PROPERTIES FUNCTION NAME ORGANISATION DATE SIGNATURE LEAD AUTHOR Research T Associate M De Mazi re BIRA IASB 5 5 2013 CONTRIBUTING Research AUTHORS ronan A Richter Univ Bremen Associate Research M pastel LATMOS CNRS Associate Research E Hendrick BIRA IASB Associate je B Langerock BIRA IASB ssociate Research k Hocke IAP U Bern Associate Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 o twor ound e GMES Table of Contents Executive summary Contents L FOURIER TRANSFORM INFRARED SPECTROMETRY FTIR As i
16. aked functions with a half width which is a measure of the vertical resolution Typical MAX DOAS averaging kernels for the NORS products NO2 HCHO and aerosols are shown in Figure 9 Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 Example of MAX DOAS NO profile retrieval 460 nm 3 o 0 1 km 25 o 0 3 km 0 5 km 2 0 7 km 9 0 9 km 15 14 km DOFS 2 7 Altitude km 0 20 40 60 NO vmr ppb Example of MAX DOAS HCHO profile 3 o 0 1 km 0 5 km 0 7 km 9 0 9 km 1 1 km DOFS 1 8 Altitude km o 0 1 km o 0 3 km 0 5 km 0 7 km 9 0 9 km 1 1 km DOFS 1 8 Altitude km 0 5 Aerosol extinction km Figure 9 typical examples of MAX DOAS profiles and averaging kernels for NO HCHO and aerosol retrievals Figure 9 shows typical examples of MAX DOAS profiles and averaging kernels for NO HCHO and aerosol retrievals Retrieved vertical profiles and corresponding averaging kernels are shown on the left and right plots respectively They have been obtained by applying the OEM based bePRO profiling tool Cl mer et al 2010 to MAX DOAS observations at Xianghe China which is one of the candidate stations for the exportation of the NORS expertise WP10 The aerosols retrieval is Titl
17. ass factor calculated from ozone and stratospheric NO profile climatologies More details on these averaging kernel tools can be found on the home page of the NDACC UV VIS Working Group Attp www ndacc org Figure 10 shows typical examples of ozone and NO column averaging kernels calculated for 90 SZA solar zenith angle sunset at 45 N in April The wavelengths are fixed to 475 nm NO and 510 nm Qs Altitude km AVK Figure 10 Typical examples of ozone and NO column averaging kernels computed for 90 SZA sunset and 45 N in April The sensitivity of zenith sky twilight measurements to the troposphere is limited with averaging kernel values smaller than 0 5 below 8 10 km altitude It increases in the stratosphere where averaging kernel values larger than 1 are obtained in the 12 30 km altitude range indicating that these measurements are strongly weighted by the contribution of the stratosphere MAX DOAS and zenith sky twilight averaging kernels will be included in the HDF data files delivered to the NORS NDACC database Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 MOR Network of Remot sound ei the GMES Atmosph Retrieval and Impact of Aerosols The inversion of aerosol vertical profiles is based on measurements of the oxygen collision complex O which shows pronounced absorption features around 360 477 577 and 630 nm The retrieval of
18. atology of Aura MLS ECMWF reanalysis and previous GROMOS ozone profiles B 1 e L2 data use and caveats The retrieved data are marked valid using the following conditions 1 retrieval has converged 2 tropospheric attenuation is less than 0 7 3 check of the ozone profiles by a scientist filter bench produced more runaway ozone profiles than the FFTS The averaging kernel matrix and the a priori profile are saved with the retrieved profile The averaging kernel matrix describes the vertical averaging that should be used if the GROMOS measurements are compared to independent measurements or model data The horizontal averaging over the field of view is considered negligible and not taken into account B 1 f References IAP Bern reports can be downloaded at http www iap unibe ch publications P Eriksson Buehler S Davis C Emde C and Lemke O 2011 ARTS the atmospheric radiative transfer simulator version 2 Journal of Quantitative Spectroscopy and Radiative Transfer 112 155101558 ISSN 00224073 doi 10 1016 j jqsrt 2011 03 001 P Eriksson Jim nez C and Buehler S A 2005 Qpack a general tool for instrument simulation Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 and retrieval work J Quant Spectrosc and Radiat Transfer 91 47 064 doi 10 1016 jqsrt 2004 05 050 C Dumitru K Hocke N K mpfer Y Calisesi Comparison and valida
19. c number density of this constituent can be deduced from the slope of the logarithm of the ratio of the signals at the two wavelengths This technique does not require any calibration To monitor atmospheric ozone with the DIAL technique the choice of the laser wavelengths depends on the altitude range of the measurement The spectral range is chosen first in the ultraviolet where the ozone absorption is more efficient but the selected wavelengths differ according to whether the measurement is made in the troposphere or in the stratosphere for stratospheric measurements the objective is to reach the stratosphere and to detect the high ozone concentrations there Browell 1989 Papayannis et al 1990 Furthermore in the higher stratosphere one has to consider the simultaneous decrease of the ozone number density and the atmospheric number density which provides the Title Data User Guide Deliverable number D 4 2 S Revision 00 Status Final S Date of issue 08 05 2013 OR wor ound Based Ol the GMES Atmo Net Gr backscatter radiation This leads to the need for powerful laser sources in order to reach the high altitude ranges The absorbed wavelength should not be strongly absorbed in order to reach the stratosphere Most teams working on this subject use XeCl eximer laser sources which emit directly in the UV at 308 nm Uchino et al 1978 and are very powerful 100 W are commonly reached with the present systems
20. ctrometer 48 channel filter bench 1994 2011 32768 channel FFT spectrometer since 2009 B 1 b Operation mode GROMOS measures automatically The operator can remotely check the instrumental performance LabView The dewar with liquid nitrogen has to be refilled 2 3 times per week by the operator GROMOS operates in Total Power mode Calibration is performed by switching between a hot load at 312 K a cold load at 80 K liquid nitrogen and the atmospheric target The cycle is repeated every 24 seconds as shown in Figure 17 A 48 channel filter bench was used from 1994 to 2011 The overall bandwidth was 1 2 GHz with a resolution of about 200 kHz in the line center Since September 2009 a 32768 channel FFT spectrometer yields the ozone spectra with a high resolution 30 kHz over the whole bandwidth Both spectrometers were operated parallel between 2009 and 2011 in order to have an overlap The raw data called LO data are stored as binary files on a dedicated data RAID which also serves as a backup Additionally to the binary files auxiliary information such as temperatures measured by sensors in the GROMOS room various voltages of the instrument giving for example the exact mirror position are stored in text files Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 B 1 c L1 data The L1 data are the frequency and power calibrated spectra The calibration is pe
21. d improving thus the precision of the final ozone profile The equation used to compute the true photon count rate from the observed count rate is the following derived from the Poisson statistics B 1 1 x P 1 exp xP where P is the observed photon count rate P is the true count rate and x 1 Pmax with Pmax being the maximum observed count rate In the case of the high energy Rayleigh signals the parameter x used for the pulse pile up correction is adjusted for each wavelength in order to obtain the best agreement Title Data User Guide Deliverable number D 4 2 S Revision 00 Status Final EI Date of issue 08 05 2013 Network of Re Ground Based the e o GMES Atmos between the slopes of both low energy and high energy Rayleigh signals For the low energy Rayleigh signals we use the Raman signals by computing reference Rayleigh slopes from the Raman signal slopes the derived Raman ozone profile and the Rayleigh extinction correction With this technique the best agreement between the ozone profiles derived from the various wavelength pairs is obtained The final ozone profile is retrieved first by combining for each wavelength the slopes of the low energy and high energy Rayleigh signals and then by combining the Raman and the composite Rayleigh ozone profiles The altitude range where both profiles are combined depends on the stratospheric aerosol content The monitoring of the aerosol c
22. e data e g model satellite requires that these reference data undergo the same averaging of information as a function of altitude i e convolution with the averaging kernel in order to obtain comparable objects E g one does not wish to obtain an apparent bias at altitudes where the measurement has no sensitivity This averaging or smoothing of the reference data is essentially Equation 3 where x is replaced by the reference data Horizontal averaging The retrieved profiles are not measured exactly at the instruments location depending on the solar zenith and azimuth angles the line of sight differs A horizontal averaging kernel of a measurement describes the relationship between the information in the retrieved profile and its geographical location These horizontal averaging kernels are not available in the HDF data files and FTIR data users should realize that the data is not geographically located at the instruments location The users can estimate the geographical location of the information from the solar and azimuth angles that are provided in the HDF files and a ray tracing tool Google earth Figure 5 Example of the light path for a measurement at St Denis Ile de La R union with a high solar zenith angle Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 Table 2 Example of a ray tracing output for an FTIR measurement of CH4 at St Denis 20 9 S 55 5
23. e Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 performed from O4 DSCDs at one wavelength only intensities and other wavelength measurements not included The number of independent pieces of information is given by the DOFS degrees of freedom for signal The highest sensitivity is in the first layer 0 200m for the three retrievals and the vertical resolution at this altitude is about 250m At higher altitudes the kernels quickly become broader and their peak values decrease except for NO which displays also a significant sensitivity in the 200 400m layer It should be noted that for aerosols the vertical resolution and information content can be increased by combining the O differential slant column densities DSCDs and intensities at different wavelengths in the same retrieval FrieB et al 2006 These results show that the MAX DOAS measurements are mostly sensitive to the layers close to the ground in addition to the tropospheric vertical column Twilight zenith sky total ozone and stratospheric NO vertical columns are also NORS products that should be delivered to the NORS NDACC database Within the NDACC UV VIS Working Group look up tables of ozone and NO column averaging kernels have been developed based on the Eskes and Boersma 2003 approach i e the averaging kernel of a layer i can be approximated by the ratio of the box air mass factor of this layer 1 and the total air m
24. e line of sight s in the atmosphere In other words they provide integrated information along the line of sight which is completely determined by the geographical location of the spectrometer and the solar lunar zenith and azimuth angles associated with the spectrum The latter parameters are all included in the data files Figure 3 provides an example of a spectrum in the window 1002 1003 cm in which several ozone absorption lines are present T T T T T T T T vni CE Ng l A l Y f a 9 AP bet 1 1 27 H ex AP 4 3 s E 2 08r 4 o or 4 0 4 xi K pae Y Ozone absorption lines ot 1 d 4 D 1 a2 i L 1002 1 1002 2 1002 3 10024 1002 5 10026 1002 7 1002 8 10029 1003 1003 1 Wavenumber env Figure 3 Example of the spectral microwindow 1002 1003 cm which contains several ozone absorption lines from a spectrum taken at St Denis Ile de La R union The retrieval process or inversion L1 L2 consists of extracting from the spectra the information about the absorbers concentrations and vertical distributions in the atmosphere based on the basic radiative transfer equations Schwarzwild s equation 1 Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 Q twor ound e GMES In the solar absorption case the only source term J
25. e weather conditions Systematic uncertainty 0 5 at 10 km to about 4 at 30 km and 5 in the upper stratosphere Daytime nighttime Nighttime Weather conditions lidar measurements require clear sky conditions since laser radiation is rapidly absorbed by clouds Only cirrus can be tolerated for accurate stratospheric ozone measurements Interferences contamination payload None Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 spectral Bottlenecks limitations Large heavy and expensive instrument When placed in a container lidars can be transported Absolute or calibration needed Self calibrating technique no need of instrumental constants Corrections needed No Auxiliary data Pressure Temperature profiles from local observations or model Averaging kernels None A priori information None Spectroscopic parameters O cross section from Bass and Paur 1985 is presently used Future change of ozone cross section is considered depending on IGACO O3 recommendation Transportability Suitability for campaign Transportable if placed in a large container System availability Commercial laser and data acquisition system lab made optical receiving system telescope and spectrometer lab made Data processing time L2 data are produced the day following the
26. ed from the spectrum continuum Ingold et al 1998 Pressure broadened ozone line spectrum T f Inversion of the line spectrum into the ozone profile by optimal estimation method OEM level2 data mmm Vertical profile of ozone volume mixing ratio which is a combination of a priori information and measurement Figure 18 Flow chart of the data retrieval Figure 18 shows a flow chart of the data retrieval The retrieval chain can slightly change from institute to institute e g in case of OZORAM the water vapour continuum is simulated by means of radiative transfer and an apriori profile Title Data User Guide Deliverable number D 4 2 f O R S Revision 00 Status Final Network o f Remote Sensing E Date of issue 08 05 2013 B Ozone microwave radiometers of NORS GROMOS and OZORAM B 1 GROMOS Ground based Millimeter wave Ozone Spectrometer B 1 a Instrument fiche Table 6 GROMOS instrument fiche Location Bern Switzerland Latitude Longitude Altitude 46 95 N 7 44 E 577m Direction of view North East Elevation of antenna 40 Mode of Operation Total power Temperature of Mixer 294 K uncooled room temperature System noise temperature 2520 K Frequency of ozone line 142 17504 GHz Target species O5 aux Quantities Opacity Altitude Range of target species 25 70 km Time resolution 30 min FFTS 60 min filter bench Spe
27. ed in the table below Although the radiative transfer simulations were performed for a fixed SZA of 60 they are roughly representative for SZA lt 70 Finally it should be noted that there is a clear geometric relationship between the height and horizontal distance of the air mass for which MAX DOAS observations are sensitive These relationships depend on elevation angle see Figure 14 below Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Network of Remote Sensing s pur duced Date of issue 08 05 2013 360 nm 1 360 nm 3 80 4 80 m 100m E 100m m 200m m 200m m 500m zs B 500m Eco 1g 1000 m 60 4g 1000 m o m 2000m P m 2000m o o E c c o o 540 540 P s c t o o E N 520 520 X Ss al WW Li 0 r 0 0 2 4 6 8 0 2 4 6 8 O4 DAMF O4 DAMF 630 nm 1 630 nm 3 80 4 80 4 EH 100m m 100m n5 m 200m m 200m P m 500m m 500m 60 BH 1000m 60 m 2000 m N o N o Horizontal distance km Horizontal distance km A eo O4 DAMF O4 DAMF Figure 13 Relationships between the retrieved O4 DSCD and the horizontal sensitivity range for selected elevation angles and wavelengths SZA 60 relative azimuth angles 0 90 180 The different colours represent results for different aerosol extinction box profiles Polynomial coefficients y ax bx c for diffe
28. eliverable number D 4 2 f O R S Revision 00 Status Final ER Date of issue 08 05 2013 Ground Based Observ the GMES Atmospher Exposure times depend on instrument type and illumination conditions and vary from milliseconds to seconds To increase the signal to noise ratio several measurements are averaged typically over several minutes In MAX DOAS applications a series of measurements is taken at different elevation angles typical values being 1 2 3 4 5 6 7 8 9 10 15 30 90 elevation Additional viewing direction at different azimuths can be taken for horizontal gradients A compromise has to be taken between minimising atmospheric changes between measurements short measurements and high signal to noise for the individual observations longer measurements Instruments are usually fully automated and programmed providing data through internet access or direct download Many instruments are also equipped by video cameras to facilitate data analysis with respect to viewing conditions and identification of disturbances As part of the measurement programme calibration measurements for characterisation of detector dark signal are taken either with a shutter or at night and some instruments also perform regular line lamp measurements for instrument line shape monitoring ok Qu m A zenith sky 1 elevation o o Intensity Arbitrary Units 104 O m A Oo 400 425 450 47
29. ent in the case of the OHP Observatoire de Haute Provence in France lidar instrument Both the precision and the vertical resolution profile depend on the experimental configuration The precision can vary from one measurement to the other 44 Title Data User Guide Deliverable number D 4 2 R Revision 00 Status Final Date of issue 08 05 2013 NO Network of Rei Ground Based Ol the GMES Atmo EXECUTIVE SUMMARY NERS twork of und Bas e GMES A CONTENTS Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 Fourier transform Infrared Spectrometry FTIR A Instrument fiche Table 1 FTIR Instrument fiche Adapted from ISSI 2012 Annex A 1 3 Instrument Fourier transform infrared spectrometer Michelson type interferometer Platform ground based Measuring technique Solar or lunar absorption spectrometry Observation geometry Looking directly at the center of the sun or the moon Units Total columns mol cm2 and volume mixing ratio per atmospheric layer vmr and partial column per atmospheric layer mol cm2 Vertical resolution A few km to 10 km Horizontal resolution Depending on solar zenith angle of measurement and vertical profile of the target species the horizontal resolution decreases as the SZA increases and if the target gas is located higher in the atmosphere Temporal resolution D
30. epending on the spectral resolution and number of interferometer scans per spectrum the higher the spectral resolution and the number of scans per spectrum the worse the temporal resolution Vertical range 0 70 km Horizontal range about 5x5km at 50 km Stability drift avoided by instrument line shape verifications with a known cell measurement typically HBr or N20 Precision Systematic uncertainty Mainly determined by spectroscopic uncertainties 5 20 Daytime nighttime Only daytime for solar absorption nighttime data with lunar absorption are generally less precise Weather conditions Stable optical depth is required in FOV essentially clear sky is required Interferences contamination payload spectral Minor contaminations due to spectroscopic interferences with other species like H2O CH4 In general they are minimized Bottlenecks limitations Large heavy and expensive instrument limited or no transportability open view to the sun is required all day air conditioned room is required The instrument must be operated with a Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 reliable suntracking system Absolute or calibration needed Self calibrating technique differential absorption principle Corrections needed No Auxiliary data Pressure Temperature profil
31. es from local observations or NCEP Averaging kernels Important component of the retrieval products L2 give information about sensitivity of the data products to the true and the a priori profiles A priori information A priori information on atmospheric vertical profiles for target and interfering species is required in the L1 gt L2 retrieval process taken from WACCM output sometimes adjusted via a dedicated pre fit of observed spectra Spectroscopic parameters from spectroscopic databases HITRAN or pseudolines from JPL G Toon or specific databases Transportability Suitability for campaign Bruker 120 125 M is transportable and therefore suitable for campaigns Bruker 120 125 HR are not transportable unless if installed in a transportable container System availability Commercial spectrometers Data processing time The goal is to deliver L2 data within 1 month after spectra acquisition Additional products Interfering species concentrations in particular HO Future potential Delivery of more species more information about isotopologues for some species H20 CO CH delivery of horizontal averaging kernels Caveats Averaging kernels vertical and horizontal and a priori information required for proper interpretation of the L2 data Title Data User Guide Deliverable number D 4 2 N ORS Revision 00 Status Final Date of issue 08 05
32. es of stratospheric ozone at NIES Tsukuba 36N 140E Proc 17th ILRC Sendai Japan 1994 T J McGee M Gross R Ferrare W S Heaps and U N Singh Geophys Res Lett 1993 20 955 958
33. evision 00 Status Final Date of issue 08 05 2013 Palm M Melsheimer C No l S Heise S Notholt J Burrows J amp Schrems O Integrated water vapor above Ny Alesund Spitsbergen a multi sensor intercomparison Atmos Chem Phys 2010 10 1 12 Ozone DIAL A Instrument fiche Table 8 Ozone DIAL instrument fiche Instrument The O lidar Light Detection and Ranging is an active remote sensing instrument Platform Ground based Measuring technique Differential Absorption Laser technique DIAL which requires the simultaneous emission of two laser beams Observation geometry zenith Units O number density profiles mol cm volume mixing ratio profiles vmr partial column mol cm Vertical resolution Increasing from 0 5 km at 20 km to 6 km at 50 km Horizontal resolution Depending on the power and the repetition rate of the laser an ozone measurement lasts typically four hours leading to a spatial resolution of the order of 200 km depending on the atmospheric wind conditions Temporal resolution 4 hours of measurements Vertical range 10 50 km Horizontal range none Stability drift Lidar ozone measurements are self calibrated Long term drift with respect to other measurement time series show values close to zero at most altitudes Nair et al 2012 Precision from 1 at 20 km to 1096 5046 at 50 km depending on the systems and th
34. f issue 08 05 2013 MOR Network of Remot ound Based Obset the GMES Atmosph kernel close to zero tells you that you re almost reproducing the a priori in other words the measurements have not added a lot of information The averaging kernel also provides you the information about the vertical resolution the vertical resolution cannot be expressed as a single number rather it is described by the convolution of the true profile with the averaging kernel Both x and A are provided in the data files A determines the so called smoothing error of the retrieval products as described in the Guide to Data Uncertainties F Including concept examples of horizontal vertical averaging Vertical averaging O3 example retrieval profile EE Aprori profile for O3 Retrieved profile for O3 O3 example averaging kernel in VMR VMR units rel to the apriori d T T I I T I Sensitivity sumof AVK rows scaled with 1 10 0 I H Ve e M M NS Height km Height km Pressure hPa Height km 10 12 0 H 0 10 0 05 0 00 0 05 0 10 0 15 0 20 0 25 0 30 4 6 8 VMR ppmv Figure 4 Example of ozone retrieval left plot green profile is the a priori blue profile is the retrieved one and associated averaging kernel in VMR VMR units right plot The dashed curve in the latter plot represents the sensitivity curve see text The ab
35. f the retrieved vertical profiles x z expressed as a volume mixing ratio VMR on a vertical altitude grid In addition the data files also provide the integrated profiles or total columns and the partial columns per altitude layer defined by the layer altitude boundaries With each variable the associated random systematic and total uncertainty is provided see Guide to Data Uncertainties Since water vapour is an important interfering gas in the infrared and since it is important to distinguish between the dry air VMR and the wet air VMR the concentration profiles of HO are also provided in the data files One must be careful as to whether the VMR is specified as an effective mean VMR in the corresponding altitude layer defined by the altitude boundaries or as a VMR on one of the layer boundaries this is explained in the variable descriptions associated with the ALTITUDE ALTITUDE BOUNDARIES MIXING RATIO and COLUMN PARTIAL variables in the data files One must be well aware about the interpretation of the retrieved vertical profiles The above equation 3 tells you how the retrieved profile is related to the true profile and what the contribution is of the a priori in the retrieved profile An averaging kernel close to the identity matrix tells you that the retrieval is close to the truth and the a priori contribution is very small An averaging Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date o
36. ision of SCs by appropriate air mass factors either from geometrical considerations or more accurately from radiative transfer calculations 2 Formal inversion of a series of measurements taken under different conditions observation geometries for tropospheric columns and profiles solar zenith angles for stratospheric columns and profiles using Optimal Estimation in combination with a priori assumptions on the vertical profile of the substance of interest and its variability The resulting lv2 product is the atmospheric profile together with its uncertainty and the averaging kernel 3 Inversion of a series of measurements using a parameterised approach without a priori information The resulting lv2 product are parameters characterising the atmospheric profile of the species for example mixing height and their uncertainties Title Data User Guide Deliverable number D 4 2 MOR S Revision 00 Status Final Date of issue 08 05 2013 the GMES Atmospheric S NO Slant Columns in Bremen May 24 2012 200 E o 8 150 o E e 100 a Oo 2 50 fe Z B ds 3 5 8 10 13 15 18 20 Time UT Figure 8 Example NO differential slant columns 1v2a Figure 8 is an example of NO differential slant columns via measured in Bremen on May 24 2012 All data are relative to the noon zenith observation the gap around 18 00 UT is to avoid direct sunlight to enter the telescope The larger columns in the lower elevation angles
37. l signal and an electronic acquisition system The analysing systems used to digitize the electronic signal provided by the photomultipliers include photon counting and or transient analysers cf figure 20 Title Data User Guide Deliverable number D 4 2 N O R S Revision 00 Status Final Network of Remote Sensing S e L SE Date of issue 08 05 2013 s GMES Atm Background radiation Altitude ct 2 v N Background signal v Altitude ace Aerosol Mie Y scattering Rayleigh scattering Lidar signal Backscattered intensity Photodetectors Laser Telescope Figure 20 Schematic view of the principle of a lidar system In the case of DIAL systems using the emission of two laser wavelengths the optical receiving system comprises spectral analyzing optics such as interference filters or spectrometers The Differential Absorption Lidar DIAL technique uses the absorption properties of a given atmospheric constituent to deduce its atmospheric concentration Laser beams at two different wavelengths are sent into the atmosphere The wavelengths are chosen so that one of them is significantly more absorbed wavelength ON than the other wavelength OFF The difference in the absorption along the beam path causes the returned lidar signals to yield a different altitude dependence Knowing from laboratory work the absorption cross sections of the constituent at both wavelengths the atmospheri
38. m Stability drift avoided by calibration with a cold and hot load Precision 5 940 km 1096 60 km based on satellite validation Systematic uncertainty 5 10 Daytime nighttime independent of day or nighttime Weather conditions not critical unless severe humidity or precipitation Interferences contamination payload spectral electromagnetic interference from communication signals Bottlenecks limitations high tropospheric humidity Absolute or calibration needed Calibration with liquid nitrogen needed in regular intervals Corrections needed no Auxiliary data Temperature profiles from radiosondes and or Re analysis Averaging kernels Important component of the produced data give information about measurement and a priori content A priori information a priori info for ozone needed e g from climatology Spectroscopic parameters from spectroscopic databases JPL and HITRAN Transportability Suitability for campaign Compact systems exist soon for campaigns System availability n a Data processing time n a Additional products opacity at the used microwave frequency Future potential traveling standard compact instrument for validation campaigns cheaper technology allowing to build more instruments Caveats Averaging kernels required for proper interpretation Table is similar to Fact sheets in Kampfer 2013
39. microwave absorber T 313 K Rotating mirror as a switch for the radiation source Calibration cycle Cold Sky Hot 24 seconds Martin Puplett interferometer MPI suppresses the image band 149 GHz and selects the strong emission line of ozone at 142 GHz Microwave signal is mixed down to an intermediate frequency IF signal of 3 7 GHz FFT spectrometer measures the voltage spectra level0 data L Vc f and V f and V f as a function of channel or frequency Figure 17 Flow chart of the measurement process The ozone microwave radiometer provides three voltage spectra cold load hot load and the atmosphere with a strong ozone emission line These data are the levelO data Title Data User Guide Deliverable number D 4 2 nN O R S Revision 00 Status Final Network of Remote Sensing Sensin SE Date of issue 08 05 2013 A 3 Data analysis From voltage spectra level 0 to vertical ozone profiles level 2 level0 data In the Rayleigh Jeans limit one can assume that the measured intensity is linearly dependent on the target temperature The receiver output voltage is calibrated in units of antenna temperature using the hot and cold load i T ot 7T Tes levell data L Tal a E Va Veota Teota gt Vhot Veola L Corrections for Attenuation by styrofoam window Attenuation of ozone emission by tropospheric water vapour opacity is determin
40. n 10 minutes for stratospheric columns at twilight typically 15 30 minutes for profile in the troposphere Vertical range 0 70 km Horizontal range 0 50 km in the troposphere Stability drift avoided by thermal stabilisation use of zenith reference spectra and instrument line shape verifications with spectral measurements and or numerical determination of slit width Precision 22 Systematic Determined by spectroscopic uncertainties 5 10 and radiative transfer uncertainty uncertainties 10 20 Daytime nighttime Only daytime Weather conditions Best measurements at clear sky good tropospheric profiles at homogeneous cloud conditions stratospheric columns nearly independent of weather conditions Direct sun observations only possible if solar disk is visible Interferences contamination Spectral interferences for weak absorbers at low concentrations possible NORS letworl E CH M e GMES Atm Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 payload spectral Bottlenecks limitations Relatively sensitive instrument air conditioned room is required for many research grade instruments tracker used High aerosol load and broken clouds limits accuracy and resolution of tropospheric profiles Absolute or calibration needed Self calibrating technique differential absorption p
41. n 00 Status Final Date of issue 08 05 2013 d Altitude km 20 Mu e 0112 03 03 04 22 06 11 07 31 099 11 08 12 28 Date mm dd of year 2010 Figure 19 Time series of strato mesospheric Ozone measured using the OZORAM B 2 e L2 data use and caveats The retrieved data are marked valid using the following conditions 1 retrieval has converged 2 line center of the O3 emission is properly fitted failure to do so points to an instability in the system 3 the atmospheric background is below 200 K 4 the standing waves are below 10 times of the noise level 5 theretrieved water vapour column is positive 6 there are no strong negative overshoots in the retrieved profile The averaging kernel matrix and the a priori profile are saved with the retrieved profile The averaging kernel matrix describes the vertical averaging that should be used if the OZORAM measurements are compared to independent measurements or model data The horizontal averaging over the field of view is considered negligible and not taken into account B 2 f References For more information and examples compare Palm M Hoffmann C G Golchert S H W amp Notholt J The ground based MW radiometer OZORAM on Spitsbergen description and status of stratospheric and mesospheric O3 measurements Atmos Meas Tech 2010 3 1533 1545 ops twork of und Bas e GMES A Title Data User Guide Deliverable number D 4 2 R
42. ng in order to increase the signal to noise ratio Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 D L1 gt L2 data processing principles Several corrections are applied to the averaged signal such as the background correction in which the background light is estimated using a linear regression in the altitude range where the lidar signal is negligible 80 150 km and the dead time correction effect in order to account for the saturation of the photon counting signals in the lower ranges The ozone number density is retrieved from the derivation of the logarithm of the corrected lidar signals according to the following equation A d P z Py 03 772 Aogs Z dz Pz z Pp 6193 Z where nO3 z is the ozone number density at altitude z P A z is the number of detected photons at wavelength A backscattered from altitude z Py is the background radiation at wavelength A and Aoos Z corresponds to the differential ozone absorption cross section 603 A1 Z Go03 A2 Z Ozone absorption cross sections depend on atmospheric temperature and thus on altitude nos z is a correction term depending on absorption by other constituents and Rayleigh and Mie differential extinction and scattering 6no3 z is expressed as follows 1 id B2 No3 z Aoss 2 E Kasel Es Aa z m Z AdeNe e where f Aj Z is the total atmospheric backscatter coefficient at wavelength A and al
43. nge can become very large gt gt 100 km However such long distances are associated with air masses at rather high altitudes Here we focus on altitudes lt 2 km for which MAX DOAS observations are most sensitive At these altitudes the horizontal sensitivity ranges are lt 83 km 1 elevation angle lt 52 km 2 elevation angle and lt 36 km 3 elevation angle Thus we limit this exercise to horizontal sensitivity ranges lt 80 km Note that horizontal sensitivity ranges gt 40 km only occur for very low aerosol optical depths lt 0 005 For such distances also the effect of the earth s curvature is small lt 130m In the following we consider elevation angles of 1 2 and 3 for which the horizontal sensitivity ranges for atmospheric layers below 2 km is largest In Figure 13 relationships between the retrieved O DSCDs and the horizontal sensitivity ranges derived from radiative transfer simulations are shown The results are obtained for a fixed SZA of 60 relative azimuth angles of 0 90 and 180 and for different aerosol layer heights Results for elevation angles of 1 and 3 and wavelengths of 360 nm and 630 nm are shown The blue lines indicate polynomial fits degree 2 to the results for an aerosol profile extending from 0 2000m which can be used as upper limit for the horizontal sensitivity range Polynomial coefficients for these results and also for additional wavelengths and elevation angles are present
44. ngs of the Quadriennal Ozone Symp Halkidiki 1985 Greece p 606 D Reidel Hingham MA Godin S G M gie J Pelon Systematic Lidar Measurements of the Stratospheric Ozone vertical Distribution Geophys Res Letters Vol 16 No 16 547 550 1989 Godin S A Carswell D Donovan H Claude W Steinbrecht S Mcdermid T Mcgee M R Gross H Nakane DPI Swart J B Bergwerff O Uchino P Von Der Gathen R Neuber Ozone Differential Absorption Lidar Algorithm Intercomparison Appl Opt Vol 38 30 6225 6236 1999 Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 Godin Beekmann S J Porteneuve A Garnier Systematic DIAL ozone measurements at Observatoire de Haute Provence J Env Monitoring 5 57 67 2003 Nair P J Godin Beekmann S Froidevaux L Flynn L E Zawodny J M Russell IIL J M Pazmino A Ancellet G Steinbrecht W Claude H Leblanc T McDermid S van Gijsel J A E Johnson B Thomas A Hubert D Lambert J C Nakane H and Swart D P J Relative drifts and stability of satellite and ground based stratospheric ozone profiles at NDACC lidar stations Atmos Meas Tech 5 1301 1318 doi 10 5194 amt 5 1301 2012 2012 7085 7091 S Godin G M gie and J Pelon Geophys Res Lett 1989 16 16 547 550 H Nakane N Sugimoto S Hayashida Y Sasano and I Matsui Five years lidar observation of vertical profil
45. nstrument fiche ten Patience oet eter Ren hte YRER DRE ENEE EERSTEN ENEE 7 Be Op ration mode E 9 EN E C E 11 D L1 L2 data processing princdples esee eene nnne nennen nnns 11 E LD data and se Caveats 2 ccce oer te Ense ege rien Done Fe ee er eee x Uere 12 F Including concept examples of horizontal vertical averaging eeeee 13 Gs RETEREMCOS Em 15 Il DOAS MAXDOAS A Instr ment fi clie cs t rv T ELEME ti evess ado Cadac ree En 16 B Operation Ru Le TEE 18 Cr MW EE 19 D L1 gt L2 data processing principles 20 E L2 data and use caveats including concept examples of horizontal vertical averaging 21 Fis References iie see a io e Eege Eege ENEE EE EES E 28 III OZONE MICROWAVE RADIOMETRY A Intro general esen tremit n tees ad died tee rure cae aces vs dada dusnuce ge 29 A 1 Instrument fiche 29 A 2 Measurement technique 30 A 3 Data analysis 32 B Ozone microwave radiometers of NORS GROMOS and OZORAM 33 B 1 GROMOS Ground based Millimeter wave Ozone Spectrometer 33 B 2 OZORAM 35 IV OZONE DIAL A Instr ment tiche ccce petere eaa a dE uou pena exu EERSTEN ga dae ka ERR Ea 38 B Operation mode cerei tei ehem ciun Ses RE eum ER sb ave E vast uiae RUE Td Ue M eR RE do ERE HN E E 39 Gy WL athe ease EE 41 D L1 gt L2 data processing principles nennen eene nnn nana snas nnns 42 E D datarandiuse caveats hdf ie ote ri optet ex Er t IRR ARENS EEN 43 F Including concept examples of horizon
46. of Lambert Beer s law for many wavelengths in parallel I A 1 A exp t oad ous Here I is the measurement spectrum and I is a background spectrum often a zenith sky observation taken with the same instrument either at noon for stratospheric retrievals or very close in time to the current measurement for tropospheric MAX DOAS observations A reference spectrum is needed to remove the effect of Fraunhofer lines which dominate the spectra recorded The absorption cross section o is taken from spectroscopic data bases and the integral over the absorber density p along the light path is the slant column density SCD In the atmosphere several absorbers have to be taken into account as well as scattering The effects of elastic scattering are accounted for as closure polynomials in wavelength inelastic scattering is corrected using pseudoabsorbers derived from radiative transfer calculations I 4 In o A SCD gt c WER i p In order to improve the detection limit and the accuracy of the results a non linear component is included in the fit allowing spectral alignment between the two spectra used For absolute wavelength calibration alignment to a high resolution solar spectrum is performed sometimes coupled to a fit of the instrument slit function The second step retrieval of atmospheric vertical columns or profiles can be performed in different ways including 1 Conversion to vertical column densities by div
47. of a pointable telescope connected to a spectrometer via quartz fibre bundle and connected to a temperature stabilised grating spectrometer equipped with a CCD detector Miniaturized systems exist that integrate all components into one box The example shown is for the IUP UB instrument used during the CINDI intercomparison campaign it has two channels one for the UV and one for the visible part of the spectrum In a Multi AXis or MAX DOAS instrument light is guided into the spectrometer by a telescope that can be pointed at the sun or at different parts of the sky Depending on the instrument and application different operation modes can be used 1 Zenith sky operation for total columns stratospheric profiles and tropospheric columns with low sensitivity 2 Direct sun operation for total columns and in combination with scattered light observations for atmospheric profiles 3 Multi Axis operation with multiple viewing directions above the horizon for tropospheric profiles and if azimuthal pointing is possible horizontal gradients Depending on application one or several spectrometers are connected to the telescope via quartz fibre optics covering parts of the spectral range from 320 600 nm with spectral resolution of typically 0 2 1 nm The spectrometers are usually equipped with cooled CCD detectors Spectral filters are used to reduce straylight from wavelengths outside the spectral region of interest Title Data User Guide D
48. of the spectral microwindow 1002 1003 cm which contains several ozone absorption lines from a spectrum taken at St Denis lle de La R union eeeeeeee 11 Figure 4 Example of ozone retrieval left plot green profile is the a priori blue profile is the retrieved one and associated averaging kernel in VMR VMR units right plot The dashed curve in the latter plot represents the sensitivity curve see text sssssessessesssseeeennee nennen nnne rnnt nnne n nnns 13 Figure 5 Example of the light path for a measurement at St Denis lle de La R union with a high solar zenith anple NRI Lu EE 14 Figure 6 Experimental setup eene enne aaa e a senses sense seii sagas ganan 18 Figure 7 Example of two spectra taken during the CINDI campaign in Cabauw sseeeeee 19 Figure 8 Example NO differential slant columns via 21 Figure 9 typical examples of MAX DOAS profiles and averaging kernels for NO HCHO and aerosol Edu Lm 22 Figure 10 Typical examples of ozone and NO column averaging kernels computed for 90 SZA sunset and SEP ed TI 23 Figure 11 Example for retrievals top and averaging kernels bottom of the aerosol extinction profile based on synthetic measurements ueesessseseeeeeeeeee enn nnn nnns annes nennen nennen nnn 24 Figure 12 Example for the impact of the aeros
49. ol extinction profile on the NO2 retrieval Left Aerosol extinction profile middle NO2 Box Airmass Factors right NO2 averaging kernels 25 Figure 13 Relationships between the retrieved O4 DSCD and the horizontal sensitivity range for selected elevation angles and wavelengths SZA 60 relative azimuth angles 0 90 180 The different colours represent results for different aerosol extinction box profiles 27 Figure 14 Relationships between altitude and horizontal distance of an air mass observed by MAX DOAS observations for different elevation angles The effect of the earth s curvature is taken into ACCOUNT m 28 Figure 15 A typical ozone microwave radiometer GROMOS at Bern 30 Figure 16 Frontend with quasi optics of the microwave radiometer sess 30 Figure 17 Flow chart of the measurement process sss ener nini ananas 31 Figure 18 Flow chart of the data retrieval cesses inunan eiai nnns 32 Figure 19 Time series of strato mesospheric Ozone measured using the OZORAM 37 Figure 20 Schematic view of the principle of a lidar system 40 Figure 21 Temporal signal averaging in order to increase the signal to noise ratio 41 Figure 22 Precision and vertical resolution profile of an ozone measurem
50. ontent in the stratosphere is made by computing the backscatter ratio defined as the ratio of the total backscatter coefficient to the Rayleigh backscatter coefficient at 355 nm using the Klett method This allows us to check the presence of aerosol layers due to small volcanic eruptions reaching the lower stratosphere or the presence of subvisible cirrus In background aerosol conditions the combination of the Rayleigh and Raman ozone profile is made around 14 15 km Finally both the Raman and composite Rayleigh profiles are corrected from the Rayleigh extinction using composite pressure temperature profiles E L2 data and use caveats hdf In addition to the number density profiles the data files also provide the volume mixing ratio profiles the integrated profiles or total columns in the valid domain With each variable the associated random systematic and total uncertainty is provided see Guide to Data Uncertainties At OHP station v For each ozone profiles the user must take the data in the valid domain defined in the metadata and variable note in the HDF files Y Pressure and Temperature profiles used for the ozone retrieval are a composite of various models For NRT data Daily P and T from Arletty model For consolidated data Daily P and T from local sounding NCEP MAP85 At Reunion station v For each ozone profiles the user must take the data in the valid domain defined in the metadata and variable no
51. orological data are stored at a high frequency of order 1s In some cases the spectral radiances are calibrated against a blackbody see ISSI 2012 interferogram measurement on April 24 2012 Spectrum measured on April 24 2012 Intensity a u e Intensity a u o ne ode oed scidit teme 02 ML 0 02 0 03 0 04 0 05 2500 2600 2700 2800 2900 3000 OPD em Wavenumber cmi 03 Figure 2 Example of an interferogram and associated spectrum in the spectral range 2450 3200 cm 1 recorded on April 24 2012 at St Denis lle de La R union 21 S 55 E approximately sea level Title Data User Guide Deliverable number D 4 2 N ORS Revision 00 Status Final ER Date of issue 08 05 2013 twoi moti Ground Based Observations for GMES Atmospheric Serv C L1data As explained above the L1 data are spectra covering a given spectral bandwidth Some preprocessing is performed before they are ingested in the inversion to derive the L2 products The preprocessing essentially includes re formatting calculation of the solar zenith and azimuth angle characterizing the spectrum synchronization between the spectra and the meteorological data and rejection of bad spectra based on the meteorological parameters and the detector DC signal D L1 L2 data processing principles The observed spectra as a function of wavenumber v are representative of the absorption of the solar beam along th
52. ove picture presents a typical averaging kernel AVK matrix for an O retrieval The AVK matrix is defined on the same vertical grid as the retrieved profile The colored curves in the plot are the rows of the AVK matrix where each element in a row is plotted against the corresponding height grid Each curve or row of the AVK is color coded according to the height of the corresponding row index see horizontal lines The sensitivity curve represents the fractional sensitivity of the retrieved profile at each altitude to the measurement The AVK matrix determines how the retrieved profile is related to the true and the a priori profiles according to Eq 3 For example the retrieved profile at 40 km altitude is obtained from Eq 3 with the row of AVK corresponding to 40km i e the yellow curve in the AVK plot in Figure 4 The yellow curve has a peak at 40km but has non vanishing terms on the nearby altitude layers Ideally each row has a single discrete peak at its corresponding height but in OEM the retrieved information at a certain altitude is obtained also from nearby layers And at higher altitudes there is no Title Data User Guide Deliverable number D 4 2 f O R S Revision 00 Status Final Ee Date of issue 08 05 2013 Net Ground Ba the GI z amp information at all the red lines tend to zero There the retrieved profile reproduces the a priori vertical profile Comparing FTIR retrieved profiles with other referenc
53. rent wavelengths and elevation angles derived from the fit to the radiative transfer results for an aerosols layer O 2000m SZA 60 relative azimuth angles 0 90 180 Title Data User Guide Deliverable number D 4 2 t Oo R S Revision 00 Status Final z E Date of issue 08 05 2013 work of Rem Ground Based Ob the GMES Atmospi wave pol coefficients pol coefficients pol coefficients length a b C a b c a b c 360nm 0 409 3 339 0 380 0 607 3 780 0 107 1 009 3 822 0 255 477nm 0 101 4 676 0 301 0 211 5 304 0 606 1 076 2 916 1 214 577nm 0 008 5 257 0 782 0 133 5 792 0 977 0 922 3 502 0 874 630nm 0 036 5 588 1 000 0 106 5 988 1 092 0 807 3 960 0 588 3 height_0 height 1 height 2 v neignt s x height 6 o o E 0 0 10 20 30 40 50 Horizontal distance km Figure 14 Relationships between altitude and horizontal distance of an air mass observed by MAX DOAS observations for different elevation angles The effect of the earth s curvature is taken into account F References Cl mer K Van Roozendael M Fayt C Hendrick F Hermans C Pinardi G Spurr R Wang P and De Mazi re M Multiple wavelength retrieval of tropospheric aerosol optical properties from MAXDOAS measurements in Beijing Atmos Meas Tech 3 863 878 2010 Connor B J Siskind D E Tsou
54. rformed offline as well as the retrieval The L1 data are calculated using the total power formula and the measured temperatures of the hot and cold black body The L1 data are calibrated and temporally integrated For the standard retrieval one spectrum is available per 30 minutes The calibrated spectra are further binned averaged in the frequency range resulting in a frequency resolution of 30 kHz around the line center and a frequency resolution of approximately 80 MHz at the wings B 1 d L1 gt L2 data The L1 spectra of brightness temperature are inverted into vertical profiles of ozone volume mixing ratio These so called L2 data profiles together with necessary retrieval data are transferred to a MySQL database at the University of Bern The retrieval uses the ARTS QPACK version 2 0 software package which is dedicated to measurements in the millimeter wave region Eriksson et al 2011 QPACK is an implementation of the optimal estimation method to invert ill posed functions Eriksson et al 2005 There is a tropospheric correction which takes the absorption of the stratospheric ozone emission by tropospheric water vapour into account The tropospheric correction is described by Peter 1997 and Ingold et al 1998 Tropospheric opacity at 142 GHz is a spin off of the tropospheric correction ECMWF reanalysis and meteorological station data are used as auxiliary data The ozone apriori climatology is a mixture of an ozone clim
55. rinciple Corrections needed No Auxiliary data No Averaging kernels Important component of the retrieval products L2 give information about sensitivity of the data products to the true and the a priori profiles A priori information A priori information on atmospheric vertical profiles for target and their covariances are needed in Optimal Estimation type profile retrievals Spectroscopic from spectroscopic databases parameters Transportability Depending on instrument type Mini DOAS excellent to scientific grade Suitability for campaign instruments suitable but container or air conditioned room needed System availability Commercial spectrometers for scientific grade instruments with custom built telescopes thermal stabilisation and calibration units Data processing time The goal is to deliver L2 data within 1 month after spectra acquisition Additional products Future potential Caveats Averaging kernels vertical and horizontal and a priori information required for proper interpretation of the L2 data Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 B Operation mode UV Spectrometer Y shaped optical fiber bundle Motorised table with 3 gratings Vis Spectrometer Figure 6 Experimental setup Figure 6 shows an experimental setup Instruments usually consist
56. rno Revision 00 Status Final the GMES Atmospheric Service Date of issue 08 05 2013 La Altitude km M 1 0 0 00 0 02 0 04 0 06 0 08 O10 Aerosol extinction amp 470 nm 1 km eee rey c Altitude km Altitude km ECC aL etg nC e let e la 10 20 0 2 900 02 04 06 98 10 Diff box AMF Averaging kernel a u AO km 4 4 E 0 7 3 3 0 9 E IR f E f i 1 7 g2 2 ER 1 9 3 3 3 r E E ZS 23 x x E FE 1 1 EA 2 9 3 Y 0 QE ES a T E 0 00 0 02 0 04 0 06 0 08 G10 0 12 O 14 0 10 20 30 40 Eu 0 2 D 0 2 0 4 0 6 OP Aerosol extinction amp 470 nm 1 km Diff box AMF Averaging kernel a u Figure 12 Example for the impact of the aerosol extinction profile on the NO2 retrieval Left Aerosol extinction profile middle NO2 Box Airmass Factors right NO2 averaging kernels The sensitivity of MAX DOAS measurements on trace gases is significantly affected by the presence of aerosols and clouds In Figure 12 the top panels show a scenario with an aerosol layer from the surface up to 2 km the bottom panels for an elevated aerosol profile centered around 2 km This figure illustrates the impact of the aerosol vertical profile on the performance of the NO vertical profile retrieval for an aerosol layer extending from the surface up to 2 km altitude as well as for an elevated aerosol layer centered around 2 km It can be seen from the NO Box Airmass Factor that an uplifted aerosol layer leads
57. sed was obtained empirically by calculating the filter transfer function for various filter orders The DIAL stratospheric ozone lidar profiles are thus generally characterized by a vertical resolution varying from several hundred meters in the lower stratosphere to several kilometers around 50 km cf Figure 22 Godin et al 1999 The information about the vertical resolution is provided in the HDF files in the variable O3 NUMBER DENSITY ABSORPTION DIFFERENTIAL RESOLUTION ALTITUDE ORIGINATOR PRECISION 96 0 5 10 15 20 25 30 35 40 45 50 z a lt u O RAYLEIGH LOW Z O OJN udin 204 7 15 i Gs PRECISION J RAMAN RESOLUTION C x i TEENER lf TEE e vv 9v vp nnn rer rm 0 1 2 3 E 5 6 7 RESOLUTION KM Figure 22 Precision and vertical resolution profile of an ozone measurement in the case of the OHP Observatoire de Haute Provence in France lidar instrument Both the precision and the vertical resolution profile depend on the experimental configuration The precision can vary from one measurement to the other G References E V Browell Proc IEEE 1989 77 419 432 A Papayannis G Ancellet J Pelon and G M gie Appl Opt 1990 29 467 476 O Uchino and I Tabata Appl Opt 1991 30 15 2005 J Werner K W Rothe and H Walther Appl Phys B 1983 32 113 118 Bass AM Paur RJ The ultraviolet cross sections of ozone I The measurements in CS Zerefos and A Ghazi Eds Proceedi
58. ta Figure 2 In order to increase the signal to noise ratio an optical filter in front of the detector limits the spectral bandwidth of the recorded spectra The interferogram corresponds to the AC part of the detector signal ideally the DC part is also recorded to verify the signal strength For operational measurements the ground based FTIR spectra are measured with a typical resolution of about 0 005 cm i e maximum optical path difference OPD of 180 cm which corresponds to a resolution 4 5A at 1000 cm of approx 2x10 To increase even more the signal to noise ratio several interferometer scans may be co added before transformation into a spectrum Recording of one spectrum requires between one to a few tens of minutes depending on the required spectral resolution and signal to noise ratio During the whole recording time the solar lunar intensity in the infrared must be stable This can be guaranteed only with completely clear sky In many instances and especially in remote locations the experiment is performed in automatic or remote control mode This requires knowledge about the meteorological conditions via a small meteorological station Most important meteo parameters are the presence of rain in which case the suntracker must be closed the solar irradiance to verify the solar intensity and the local surface pressure and temperature Additional parameters are wind speed and direction and local humidity The mete
59. tal vertical averaging cccccccccssseccesseeceesseeecsseeeeeens 43 CHECA M 44 16 29 38 Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 List of tables Table 1 FTIR Instrument fiche Adapted from ISSI 2012 Annex A 1 3 eene 7 Table 2 Example of a ray tracing output for an FTIR measurement of CH4 at St Denis 20 9 S 55 5 E Ile de La R union on 25 1 2011 04 04 UT for a solar zenith angle Of ei 15 Table 3 Example of a ray tracing output for O3 providing the geographical location of the points along the line of sight corresponding to a percentage of the total O3 column measurement on 25 1 2011 4 04 UT with solar zenith angle 672 15 Table 4 DOAS MAXDOAS instrument che 16 Table 5 Ozone Microwave Radiometry instrument fiche 29 Table 6 GROMOS instrument fiche 33 Table 7 OZORAM instrument fiche 35 Table 8 Ozone DIAL instrument che 38 Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 List of figures Figure 1 Experimental set p i eene ines essa er e de ek Ea a Nania a EEE seats 9 Figure 2 Example of an interferogram and associated spectrum in the spectral range 2450 3200 cm 1 recorded on April 24 2012 at St Denis lle de La R union 21 S 55 E approximately sea level 10 Figure 3 Example
60. te in the HDF files Y Pressure and Temperature profiles used for the ozone retrieval are a composite of various models For NRT data Daily P and T from Arletty model For consolidated data Daily P and T from local sounding ECMWF MAP85 F Including concept examples of horizontal vertical averaging Depending on the power and the repetition rate of the laser an ozone measurement lasts typically several hours leading to a spatial resolution of the order of 100 km depending on the atmospheric conditions Due to the rapid decrease of the signal to noise ratio in the high stratosphere it is necessary to degrade the vertical resolution of the measurement in order to limit the statistical error at this altitude range to reasonable values In the DIAL technique it is necessary to use a low pass filter in order to account for the rapid decrease of the signal to noise ratio in the high altitude range In our case the logarithm of each signal is fitted to a 2 order polynomial and the ozone number density is computed from the difference of the derivative of the fitted polynomials The smoothing is achieved by varying the number of points over which the signals are fitted The resolution is calculated from the Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 cut off frequency of the low pass filter defined at 23 dB The relation between the filter cut off frequency and the number of points u
61. tion studies related to ground based microwave observations of ozone in the stratosphere and mesosphere Journal of Atmospheric and Solar Terrestrial Physics ed Elsevier vol 68 no 7 pp 745 756 2006 K Hocke Homogenisation of the ozone series of the microwave radiometers SOMORA and GROMOS IAP Research Report No 2007 04 MW Institut f r angewandte Physik Universitat Bern 2007 K Hocke Comparison of Ozone Measurements by GROMOS SOMORA Aura MLS and Ozonesonde IAP Research Report No 2005 04 MW Institut f r angewandte Physik Universitat Bern 2005 T Ingold Peter R Kampfer N Weighted mean tropospheric temperature and transmittance determination at millimeter wave frequencies for ground based applications Radio Science vol 33 no 4 pp 905 918 1998 N K mpfer Monitoring Atmospheric Water Vapour Ground Based Remote Sensing and In situ Methods ed Niklaus K mpfer vol 10 series ISSI Scientific Report Series Springer New York http dx doi org 10 1007 978 1 4614 3909 7 2012 ISBN 978 1 4614 3908 0 2013 R Peter The Ground based Millimeter wave Ozone Spectrometer GROMOS IAP Research Report No 1997 13 Institut fiir angewandte Physik Universitat Bern 1997 B 2 OZORAM B 2 a Instrument fiche Table 7 OZORAM instrument fiche Location Ny Alesund Spitsbergen Norway Latitude Longitude Altitude 78 9 11 9 15m Direction of view AZIMUTH Elevation 113
62. titude z Aa z is the differential atmospheric extinction a 44 z a 45 z linked to Rayleigh and Mie scattering and Xe A0en Z the differential extinction by other atmospheric compounds In the DIAL technique the laser wavelengths are chosen so that the term 6n 3 z represents less than 10 of the term derived from the slope of the lidar signals in the altitude range of interest The derivation of the ozone number density from the laser signals shows thus that the DIAL technique is a self calibrated technique which does not need the evaluation of instrumental constants The ozone number density is derived from the three lidar signal pairs detected by the experimental system Rayleigh high energy Rayleigh low energy and Raman which optimizes the accuracy of the retrieved ozone profile in the high stratosphere the middle low stratosphere and the lower stratosphere respectively In condition of background stratospheric aerosol it is preferable to use the low energy Rayleigh signals in the lower stratosphere since they provide a better vertically resolved ozone profile than the Raman signals The use of these signals in the lowermost stratosphere is prevented by the saturation of the photon counters as is the use of the high energy Rayleigh signals higher up A method based on the adjustment of the parameter used for the pulse pile up correction was then designed in order to optimize the range where the most energetic lidar signal pair can be use
63. to an increase in light path at the altitudes where the aerosol is present As indicated by the averaging kernels an elevated aerosol layer results in an increase in sensitivity for NO at higher altitudes but a lower sensitivity right above the surface Horizontal averaging The horizontal range for which MAX DOAS observations are sensitive can be estimated from the measured O absorption The respective relationships between the retrieved O4 DSCDs and the horizontal sensitivity ranges can be established based on radiative transfer simulations Here we assume that the horizontal sensitivity range extends to the distance at which the O4 DAMP AMF at Title Data User Guide Deliverable number D 4 2 Revision 00 Status Final Date of issue 08 05 2013 low eg 1 elevation minus AMF at zenith decreases to Le of its value at the location of the instrument within 60 m distance The relationships between the retrieved O4 DSCDs and the horizontal sensitivity ranges depend on wavelength elevation angle and aerosol profile Thus for the different wavelengths and elevation angles separate relationships are determined see below In general larger horizontal sensitivity ranges are found for vertically more extended aerosol extinction profiles Further dependencies on SZA and relative azimuth angle are relatively small for SZA lt 70 and will be ignored here In principle especially at long wavelengths the horizontal sensitivity ra

Data User Guide

Contents

Download Pdf Manuals

Related Search

Related Contents