ENVISAT VALIDATION RESULTS OBTAINED WITH LPMA AND IASI-BALLOON FTIR

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1 ENVISAT VALIDATION RESULTS OBTAINED WITH LPMA AND IASI-BALLOON FTIR G. Dufour (1), S. Payan (1), Y. Té (1), P. Jeseck (1), V. Ferreira (1), C. Camy-Peyret (1), M. Eremenko (1, *), A. Butz (2), K. Pfeilsticker (2), W. Gurlit (3), and K. Gerilowski (3) (1) Laboratoire de Physique Moléculaire et Applications (LPMA), Université Pierre et Marie Curie, case 76, 4 place Jussieu, 752 Paris Cedex 05, France (2) Institut für Umweltphysik, Im Neuenheimer Feld 9, 691 Heidelberg, Germany (3) Institute of Environmental Physics and Institute of Remote Sensing, University of Bremen, Bremen, Germany (*) Now in Department of Chemistry, University of Waterloo, Waterloo, ON Canada, N2L 3G1 ABSTRACT/RESUME A summary of the data acquired for Envisat validation during several flights of the Limb Profile Monitor of the Atmosphere (LPMA) instrument is presented. This balloon-borne Fourier transform spectrometer was operated in various optical configurations depending of which Envisat instrument was the prime target for validation: LPMA (LWIR) for MIPAS, LPMA (SWIR) for SCIAMACHY and MIPAS, LPMA (NIR) for SCIAMACHY and GOMOS. Profiles of O 3,, O, and HNO 3 have been compared with Envisat data. Balloon profiles of other species like NO 2, NO and CO have been retrieved but the corresponding Envisat products were nor yet available. In cooperation with IUP/Bremen, we are in the process of calibrating the LPMA (SWIR) spectra to produce absolute irradiance solar spectra in bands 7 (2.0 µm) and band 8 (2.3µm) of SCIAMACHY. 1. FLIGHTS PERFORMED WITHIN ESABC With our two instruments LPMA (Limb Profile Monitor of the Atmosphere) and, we are involved in several Announcement of Opportunities (AO) projects for the ENVISAT chemistry instruments validation [1]. The LPMA instrument is a remote sensing infrared Fourier transform interferometer operating in solar occultation [2]. Three different instrument configurations can be used depending of the validated ENVISAT instrument (Table 1). The LPMA(LWIR) configuration is mainly used for MIPAS validation, the LPMA(SWIR) and the LPMA(NIR) configurations are suitable for SCIAMACHY and GOMOS validation respectively. With this dual channel output optics instrument, the main validated products are the concentration or vmr (volume mixing ratio) profiles of several infrared active stratospheric species. The IASI-Ballon instrument is based on the same interferometer as LPMA but operates in nadir and measures the atmospheric emission of the surface/atmosphere system [3]. It is used to validate the total columns measured by SCIAMACHY in its nadir mode. Table 2 summarizes the different flights performed with the configurations LPMA and of our instrument in the context of ESABC validation campaigns. Table 1 : Different configurations of the LPMA instrument. Configuration Detectors Beamsplitter Spectral range (cm -1 ) LWIR (Long Wave Infrared) SWIR (Short Wave Infrared) NIR (Near Infrared) HgCdTe InSb InSb InSb Si Si KCl ; ; CaF ; ; Quartz Table 2: Balloon flights performed during ESABC validation campaigns. Date Flight Payload Prime Envisat instrument 02/08/05 (1) IASI02 SCIAMACHY 02/08/ LPMA LPMA (NIR) GOMOS 02/08/ (1) 03/03/04 (1) LPMA LPMA (LWIR) CAESR MIPAS 03/03/ (1) LPMA LPMA (SWIR) SCIAMACHY CAESR 04/10/09 (2) LPMA LPMA (SWIR) SCIAMACHY 04/03/ (1) LPMA LPMA (LWIR) MIPAS (1) Kiruna, Sweden, (2) Aire-sur-l Adour, France 2. SCIAMACHY VALIDATION 2.1. Absolute calibration and high resolution solar spectra A new developed collimated calibration source and a NIST FEL 100W irradiance standard were used as input of the suntracker commonly shared by LPMA (IR) and DOAS (UV-vis) [4] before the balloon flight. The spectral response of the both instruments permits to calibrate balloon spectra recorded at float ( high sun ) Proceedings of the Second Workshop on the Atmospheric Chemistry Validation of ENVISAT (ACVE-2) ESA-ESRIN, Frascati, Italy, 3-7 May 04 (ESA SP-562, August 04) EPOENGD

2 on an absolute radiance/irradiance scale. SCIAMACHY Level 1b spectra recorded in the IR (band 7 and 8) and in the UV-vis (band 1 to 4) can also be validated by these absolute calibrated spectra. The calibration procedure was established and tested before the LPMA flight. A good stability of LPMA spectra (InSb detectors) with respect to time and distance of the input the collimated calibration source was observed. The high S/N spectra recorded during the LPMA flight by LPMA and DOAS instruments will be used to validate collocated SCIAMACHY Level 1b spectra. Around 800 solar line and 800 H 2 O telluric line parameters in the near infrared have been derived from spectra recorded during a previous flight, LPMA10 performed on March, 97 and from LPMA spectra [5]. These new parameters should improve the radiative transfer calculations in the band 6 of SCIAMACHY. Moreover, the LPMA10 flight had permitted to determine new spectroscopic data in the O 2 A band (760 nm) [6], which will be very useful for GOMOS SCIAMACHY nadir validation with IASI- Balloon The total columns of, O and O 3 measured during the IASI02 flight have been used to validate those measured by SCIAMACHY operating in the nadir mode the same day. Fig. 1 shows and SCIAMACHY total columns with respect to measurement location (latitude and longitude). The SCIAMACHY columns were retrieved from bands 7 and 8, the O columns from band 7 and the ozone columns from bands 1 and 2. The co-location between and SCIAMACHY measurements is rather good (< 600 km). On Fig. 2, the columns of, O and O 3 measured by are compared to the corresponding columns measured by SCIAMACHY for the different locations indicated on Fig. 1. The columns retrieved from SCIAMACHY band 8 are unphysically variable. The CO columns retrieved also in the band 8 are variable and have negative values (not shown here). The same behavior is observed for ozone columns retrieved from band 2 (Fig. 1.). So, at present, SCIAMACHY nadir products derived from bands 2 and 8 have to be considered carefully. The variability of retrieved columns in bands 1 and 7 is smaller and we can compare these columns with the columns measured by. A negative bias of about % is observed for the columns derived from the band 7. This bias becomes of the order of 60 % for O columns. Concerning ozone columns derived from band 1, the bias is positive: at present and for our conditions, SCIAMACHY nadir products overestimate ozone columns by about % Band E 2.85E 3E 3.15E 3.3E 3.45E 3.6E 3.75E 3.9E Band 7 - O Band 1 - O 3 Band 2 - O 3 2E 2.563E 3.1E 3.688E 4.E 4.813E 5.375E 5.938E 6.5E 5.6E 5.9E 6.2E 6.5E 6.8E 7.1E 7.4E 7.7E 8E -4E -2.E -5E17 1.E 3E 4.75E 6.5E 8.E 1E Fig. 1. Total columns of, O and O 3 measured by and SCIAMACHY and respective measurement location

3 total columns total columns 4.0x10 3.5x10 3.0x10 2.5x10 2.0x10 1.5x10 1.0x10 5.0x10 1x10 9x10 8x10 7x10 6x10 5x10 4x10 3x10 2x10 1x (68.10,.96) (68.10,.96) SCIAMACHY - band 7 (67.84,.57) (67.84,.57) (68.,.11) (67.57,.) (68.01,.75) (68.40,.) (68.,.11) (67.57,.) (68.01,.75) (68.40,.) (68.46,.) SCIAMACHY - band 8 (68.46,.) 3.1. LPMA flight The MIPAS profiles considered here for validation have been obtained the same day as the LPMA flight at :13 TU and for a mean position of (65.7 N, 13.4 E). LPMA profiles have been measured several hours earlier during the sunset (between 15:40 and 16:10 UT). The location of the tangent point varies between (66.7 N,.8 E) and (66.1 N, 15.6 E). The spatial and temporal co-location is rather good between LPMA and MIPAS measurements. Fig. 3 shows the comparison between LPMA and MIPAS profiles of ozone. The operational profile of ozone obtained with the version 4.61 of the retrieval algorithm presents strong oscillations. A tendency of overestimating ozone values can be observed. On the other hand, the scientific profile of ozone is smoother and has a relatively small negative bias around 8 % compared to LPMA profile. O 3 total columns O total columns 6x10 5x10 4x10 3x10 2x10 1x10 8x10 7x10 6x10 5x10 4x10 3x10 2x10 1x (68.10,.96) (68.49,.72) (68.44,.84) SCIAMACHY - band 7 (67.84,.57) (68.,.11) (67.57,.) (68.01,.75) (68.40,.) (68.46,.) SCIAMACHY - band 1 (68.,.33) (68.45,.09) (68.17,.46) (67.96,.95) (68.,.72) (68.39,.49) (67.91,.09) (67.45,.81) (67.69,.58) (67.91,.36) (68.11,.14) (68.31,.91) (68.50,.64) (68.49,17.86) (67.64,.72) (67.71,.61) (67.96,.17) (68.,.72) (68.46,.) Fig. 2. Comparison between total columns of, O and O 3 measured by SCIAMACHY and by IASI- Balloon 3. MIPAS VALIDATION WITH LPMA The validation of MIPAS products is presented here. In addition to operational products distributed by ESA, we have used scientific products from IMK (G. Stiller) for the comparison with co-located profiles of O 3, O, and HNO 3 measured during LPMA and LPMA flights. 32 LPMA sunset (66.7N,.8E) O 3 Fig. 3. Comparison between the O 3 operational profile of MIPAS (V4.61) and the O 3 scientific profile of MIPAS (IMK) and the O 3 profile measured by LPMA Fig. 4 presents the comparison between LPMA and MIPAS profiles of and O. The operational profile of O is in good agreement with the profile measured by LPMA whereas the operational profile of methane shows strong oscillations. The scientific profile of methane agrees well with the LPMA profile (falling within the range of error bars). The agreement between the MIPAS scientific profile of O and the LPMA profile is a little worse than for methane profile. The scientific profile is about % lower than the LPMA profile. The correlations between and O measured by LPMA and MIPAS (IMK) are compared with the calculated correlation derived from ATMOS outside Arctic measurements [7] on Fig. 5. The / O correlation obtained from flight LPMA agrees well with the calculated one above km. is overestimated compared to O for lower altitudes. Methane amounts measured by MIPAS (IMK) tend also to be overestimated for all the altitude range.

4 32 (66.7N,.8E) LPMA sunset 32 (66.7N,.8E) LPMA sunset HNO 3 32 (66.7N,.8E) LPMA sunset O Fig. 4. Comparison between the and O operational profiles of MIPAS (V4.61) and the and O scientific profiles of MIPAS (IMK) and the and O profiles measured by LPMA VMR (ppmv) 1.6 LPMA sunset MIPAS (IMK) ATMOS (calculated) O VMR (ppmv) Fig. 5. Comparison of the / O correlation derived from MIPAS (IMK) and LPMA measurements with the calculated correlation derived from ATMOS measurement In the case of HNO 3, the operational and scientific profiles agree relatively well, particularly for altitudes lower than km (Fig. 6). A negative shift of about 2 km is observed between these 2 profiles and the profile measured by LPMA. Fig. 6. Comparison between the HNO 3 operational profile of MIPAS (V4.61) and the HNO 3 scientific profile of MIPAS (IMK) and the HNO 3 profile measured by LPMA LPMA flight The MIPAS profiles considered here for validation have been measured the same day as the LPMA flight at :16 TU and for a mean position of (65.7 N, 12.7 E). LPMA profiles have been measured several hours earlier during the balloon ascent (between 15:13 and 16: UT) for a mean latitude of 67.4 N and a mean longitude of.1 E. The spatial and temporal colocation is rather good, however, between LPMA and MIPAS measurements. Fig. 7 shows the comparison between LPMA and MIPAS profiles of ozone. Contrary to the previous case, the operational profile of ozone derived from the version 4.61 of the ESA retrieval algorithm does not present any oscillations. Its agreement with the LPMA profile of ozone is good (falling within the range of error bars). The agreement between scientific profile of ozone and LPMA profile is also rather good except between 15 and km :51 TU (67.3N,.7E) 16: TU (66.8N,.8E) 14 MIPAS (65.7N,12.7E), :16 TU 12 15:13 TU (67.7N,.6E) O 3 Fig. 7. Comparison between the O 3 operational profile of MIPAS (V4.61) and the O 3 scientific profile of MIPAS (IMK) and the O 3 profile measured by LPMA

5 Contrary to the results of the LPMA flight, the shape of MIPAS and O scientific profiles for LPMA is very different from the shape of LPMA profiles and from the MIPAS operational profiles (Fig. 8). The structure observed near km by MIPAS (IMK) is not observed by LPMA nor by the operational MIPAS retrieval. A verification is needed however to check that the profile provided by IMK is the right one. The operational methane profile is overestimated for all altitudes. However the agreement with the LPMA profile is reasonable (near error bars). Operational O is overestimated above km and agrees relatively well below. The comparison between measured and calculated / O correlations (Fig. 9) shows that a very good agreement is obtained between LPMA and the ATMOS derived correlation. On the other hand, the correlation obtained with operational products disagrees with the calculated one for O values lower than 0.17 ppmv. An opposite behavior for the correlation obtained with scientific products is observed. The structure observed for O values around 0.17 ppmv does not seem realistic. A comparison using a CTM to scale the LPMA profile to the location and the time of MIPAS measurements would provide a firmer basis for comparison MIPAS (65.7N,12.7E), :16 UT 12 15:13 UT 10 (67.7N,.6E) : UT (66.8N,.8E) : UT (66.8N,.8E) 15:51 UT (67.3N,.7E) 15:51 UT (67.3N,.7E) MIPAS (65.7N,12.7E), :16 UT 12 15:13 UT 10 (67.7N,.6E) O Fig. 8. Comparison between the and O operational profiles of MIPAS (V4.61) and the and O scientific profiles of MIPAS (IMK) and the and O profiles measured by LPMA O MIPAS (IMK) MIPAS V4.61 (ESA) ATMOS (calculated) Fig. 9. Comparison of the / O correlation derived from MIPAS (V4.61), MIPAS (IMK) and LPMA measurements with the calculated correlation derived from ATMOS measurement 4. CONCLUSION So far, the agreement between Envisat measurements and our LPMA and measurement is reasonable. For SCIAMACHY, nadir products derived from bands 1 and 8 have to be considered carefully. For MIPAS, the scientific algorithms seem to give results, which are more stable than results obtained by the operational algorithm (less oscillations). Some improvements are needed for both scientific and operational algorithms. The validation of Envisat products for NO 2, NO and CO will be done as soon as the corresponding Envisat products are available. 5. REFERENCES 1. Camy-Peyret C., et al., Validating Envisat atmospheric products using the balloon-borne instrument LPMA (Limb Profile Monitor of the Atmosphere, ESA WPP, Vol. 6, Camy-Peyret C, et al., The LPMA balloon-borne FTIR spectrometer for remote sensing of atmospheric constituents, ESA Publications, Vol. SP-370, 3-3, Té Y., et al., Balloon-borne calibrated spectroradiometer for atmospheric nadir sounding, Appl. Opt., Vol. 4, , Ferlemann F., et al., A new DOAS-instrument for stratospheric balloon-borne trace gas studies, Appl. Opt., Vol. 39, 77-86, Eremenko M., Inversion des spectres infrarouges à haute résolution spectrale enregistrés en absorption à partir de ballons stratosphériques. Ajustement global de grands domaines spectraux. Inversion multi-paramètres (espèces moléculaires), Thèse de l université Pierre et Marie Curie, Paris 6, Camy-Peyret C., et al., Hight resolution balloonborne spectroscopy within the O 2 A-band: observations

6 and radiative transfer modelling, In IRS 00: Current Problems in Atmospheric Radiation. pp., A. Deepak Publ., Virginia, USA01 7. Michelsen H.A., et al., Correlations of stratospheric bundances of and O derived from ATMOS measurements, Geophys. Res. Lett., Vol., , ACKNOWLEDGEMENTS We are very grateful to G. Stiller from IMK/FZK who provided us with the scientific profiles of MIPAS. The co-authors of the present paper are very glad to acknowledge the contribution of I. Pépin, G. Lerille, D. Mayèle and C. Rouillé from LPMA balloon team as well as the help of M. Dorf, F. Weidner from the DOAS team. The LPMA/DOAS and payloads are benefiting from the very professional expertise of J. Evrard and his colleagues (A. Laurens, A. Pelissier and A. Vecten) from the pointing gondola department of CNES in Toulouse, France. The campaign coordinator, P. Wursteisen and the CNES and SSC launching teams played a key role in making possible the balloon flights and obtaining the results reported in this paper.