THREE VALIDATION METHODS of SCIAMACHY and MIPAS-E DATA WITH DOAS MEASUREMENTS OBTAINED by the GASCOD/A4p SPECTROMETER on BOARD the GEOPHYSICA-M55 AIRCRAFT

The aim of this paper is to present three methods for the validation of the SCIAMACHY and MIPAS-E data using the UV/Vis. DOAS spectrometer, called GASCOD/A4pi, installed on board the Geophysica M-55 aircraft, which can fly up to 20 km of altitude. The first method is the classic one of the cross-crossing that requires the temporal and spatial simultaneity of the measurements on board both the ENVISAT-1 satellite and the M55 aircraft. The second one is based on a Lagrangian approach, which allows for the identification of the best flight trajectory of the M55, on the basis of the dynamic and chemical "history" of the air masses at the aircraft altitude. In this case the comparison can be extended for longer time periods. The latter method is proposed to validate the tropospheric amounts of O-3 and NO2. In fact, from SCIAMACHY data it can be possible to infer the tropospheric amounts of minor gases subtracting the stratospheric column, detected with limb measurements, from the total column obtained with subsequent nadir measurements. In the GASCOD/A4pi data the tropospheric gases amounts are directly observed by means of the nadir measurements, if the flight altitude is close up the tropopause level