Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft C. E. Blom, T. Gulde, M. Höpfner, C. Keim, G.Y. Liu, C. Piesch and C. Sartorius Forschungszentrum Karlsruhe GmbH, Institut für Meteorologie und Klimaforschung, Postfach 3640, Karlsruhe, FRG VALIDATION OF THE ENVISAT ATMOSPHERIC CHEMISTRY INSTRUMENTS BY CORRELATIVE MEASUREMENTS OF MIPAS-STR Figure 10. Two-dimensional cross sections of the temperature and of HNO 3, CFC-11 and ClONO 2. The plots were made from 54 individual vertical profiles indicated with + at the GPS altitude of the aircraft. Symbols in the lower part of the plots indicate the lowest tangent height used in the retrieval. The lowest tangent height is 6 km or, if clouds are in the field of view, higher. The clouds are monitored by the DC output of the detectors. About 10 sequences, measured before 2.6·10 4 s UTC, have not been analysed yet. Note the subsidence observed in the cross sections of the trace species when entering the polar vortex from the edge region. Refererences [1] G.Y. Liu, C.E. Blom, T. Gulde, C. Keim, M. Höpfner, P. Loës, C. Piesch, C. Sartorius and M. Volk, Validation of MIPAS on ENVISAT by correlative measurements of MIPAS-STR, Proceedings of "Envisat Validation Workshop", December 2002, Frascati, Italy (ESA SP-531), March [2] C. Piesch, T. Gulde, C. Sartorius, F. Friedl-Vallon, M. Seefeldner, M. Wölfel, C.E. Blom, and H. Fischer, Design of a MIPAS instrument for high-altitude aircraft, Proceedings of the 2nd Internat. Airborne Remote Sensing Conference and Exhibition, ERIM, Ann Arbor, MI, Vol. II, , [3] J. W. Brault, New approach to high-precision Fourier transform spectrometer design, Applied Optics, No. 35, , [4] W. Kimmig, Das Abtastverfahren der Interferogramme des flugzeuggetragenen Fourierspektrometers MIPAS-STR, Dissertation im Fach Physik, Universität Karlsruhe, Wissenschaftliche Berichte des Forschungszentrums Karlsruhe, FZKA 6665, [5] C. Keim, Entwicklung und Verifikation der Sichtlinienstabilisierung für MIPAS auf dem hochfliegenden Forschungsflugzeug M55 Geophysica, Dissertation im Fach Physik, Universität Karlsruhe, Wissenschaftliche Berichte des Forschungszentrums Karlsruhe, FZKA 6729, [6] Trieschmann, O, Level 0 to 1b Data Processing of the MIPAS-B2 balloon borne Fourier Transform Spectrometer, Technical Note, Document: PO-TN-IMK-GS-0003, ESA-Contract No /95/NL/CN and 12078/96/NL/GS, Revision 1.2, Karlsruhe, [7] Stiller, Gabriele P. (Editor) with contributions from T. v. Clarmann, A. Dudhia, G. Echle, B. Funke, N. Glatthor, F. Hase, M. Höpfner, S. Kellmann, H. Kemnitzer, M. Kuntz, A. Linden, M. Linder, G. P. Stiller, S. Zorn, The Karlsruhe Optimized and Precise Radiative transfer Algorithm (KOPRA), Forschungszentrum Karlsruhe, Wissenschaftliche Berichte des Forschungszentrums Karlsruhe, FZKA 6487, [8] M. Höpfner, C.E. Blom, T.v. Clarmann, H. Fischer, N. Glatthor, T. Gulde, F. Hase, C. Keim, W. Kimmig, K. Lessenich, C. Piesch, C. Sartorius, and G.P. Stiller, MIPAS-STR data analysis of APE-GAIA measurements, in IRS 2000: Current Problems in Atmospheric Radiation, W. L. Smith and Yu. M. Timofeyev (Eds.). A. Deepak Publishing, Hampton, Virginia. pp , MIPAS-STR has been operated for ENVISAT validation from the high-altitude aircraft M55-Geophysica. We present results of the 22 July 2002 mid-latitude flight from Forli, Italy, close to the location of lower MIPAS-ENV tangent points for orbit In February/March 2003 an Arctic Geophysica campaign has been performed from Kiruna, Sweden, to validate gradients in the temperature and in the volume mixing ratio of the trace gases. We show examples of the MIPAS-STR measurements of the 8 March 2003 flight between Kiruna and Spitzbergen. Acknowledgement Financial support by the Bundesministerium für Bildung und Forschung for the HGF-Vernetzungsfonds Generierung und Validierung von Datenprodukten aus Envisat-Messungen sowie deren Nutzung zur Erforschung der oberen Troposphäre und der Stratosphäre (FKZ: 01SF9953) and through the Deutsches Zentrum fuer Luft- und Raumfahrt e.V. for the project Validierung von Datenprodukten des MIPAS- ENVISAT mittels Ballon-, Flugzeug- und bodengebundener Messungen (FKZ: 50EE0203), the EU-project APE-INFRA (contract EVR1-CT ) and the European Space Agency is gratefully acknowledged. MIPAS-STRatospheric aircraft: concept and strategy MIPAS-STR is a cryogenic mid IR ( cm -1 ; µm) FT emission sounder [2]. Two-sided interferograms (L = 14 cm) are measured resulting in a spectral resolution (1/2L) of cm -1. Data sampling is performed in time-equidistant mode [3] with accurate delay compensation to reduce noise due to sampling errors [4]. Low NESR, in flight < 8 nW/cm 2 ·sr·cm -1 in channel 1 ( cm -1 ) and < 4 nW/cm 2 ·sr·cm -1 in channel 2 ( cm -1 ), and accurate pointing (1 arcmin precision) [5] has been achieved. After switch-on, the instru- ment runs fully autarkic according a predefined measurement strategy. Data retrieval is made with level-1 software [6], modified for continuous calibration measurements during the flight, and the level-2 Karlsruhe Optimized and Precise Radiative transfer Algorithm (KOPRA, [7]) with appropriate inversion routines [8]. The final results are 2-dimensional distributions of the trace gases in an altitude range covering the lowest stratosphere and the upper troposphere. Figure 8. Measurement strategy Oversampled (tangent-height-sta- bilised, 1.25 km spaced) limb sounding and upward observa- tions with intermediate blackbody and deep-space measurements. Single sequences require about 2.5 min. resulting in a horizontal resolution in flight direction of 30 km. Figure 7. The MIPAS-STR mounted in the instrument-tailored dorsal bay be- hind the pilot cabin. Validation of gradients at high latitudes: Kiruna, February - March 2003 In July 2002 a Geophysica test campaign was extended with two flights aimed at an early validation of ENVISAT standard products. Below are results from the flight conducted with the so called chemistry payload, a combination of remote sensing and in-situ instruments. The results were presented at Envisat Validation Workshop in Frascati [1]. Profiles of HNO 3 and O 3 seem to agree well with the correlative measurements but vertical zigzag features, alternating for even and odd scans, are observed in the profiles of MIPAS-Envisat. This behaviour, not observed by MIPAS-STR, is mostly pronounced in the CH 4 and N 2 O data from channel B but also present in the temperature profiles derived from channel A. It is probably caused by deficiencies in the radiometric calibration of the atmospheric spectra which is independently performed for forward and backward interferometer sweeps. Validation at middle latitudes: The 22 July 2002 flight from Forli, Italy European Geophysical Society Nice, April 2003 Figure 9. The location of the tangent points of MIPAS-ENV and MIPAS-STR for the and flights. The points are colour coded depending on the tangent height (black for 6 km, red for 20 km). Note that the MIPAS-STR measurements of are in the region of the SCIAMACHY limb measurements (see table 1). # ) CFC-11 from channel 1 was used to obtain methane profiles: CH 4 = × CFC-11. The coefficients are from HAGAR (High Altitude Gas chromatograph for Atmospheric Research) measurements for the flight. Figure 1. Retrieved VMR profiles of O 3 from MIPAS- STR and MIPAS-ENV. flight flight Figure 2. Retrieved VMR profiles of HNO 3 from MIPAS-STR and MIPAS-ENV. Figure 4. Retrieved temperature profiles from MIPAS-STR and MIPAS-ENV and the ECMWF analysis. Figure 3. Retrieved VMR profiles of CH 4 from MIPAS-STR # ) and MIPAS-ENV. Figure 5. The difference between the VMR of CH 4 and the average profile of limb scans 7-17 (CH 4 CH 4 mean) for MIPAS-ENV orbit Figure 6. The difference between temperature and mean temperature (T Tmean) of MIPAS-ENV orbit Five flights were made with the Geophysica chemistry payload to validate gradients in the trace gas distributions measured by MIPAS, SCIAMACHY and GOMOS. No validation has yet been made but a few two-dimensional cross sections are shown to illustrate the measure- ments made by MIPAS-STR. Table 1. Coincidences of the MIPAS-STR and MIPAS-ENV measurements. Dive