Partenaires et organisations internationales
(Anglais)
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Univ.of Rome, IROE and Univ. of l'Aquila (I), MPI-Ch. and
Univ. of Mainz (D), Univ. of Cambridge (UK), Univ. of Stokholm (S), FMI (FIN), NILU (N)
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Résumé des résultats (Abstract)
(Anglais)
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The APE-POLECAT mission took place between 19 December 1996 and 16 January 1997. APE-POLECAT comprised the inaugural mission of the high-altitude research aircraft, M-55 Geophysica, flights by the DLR Falcon, supporting measurements from a number of Arctic ground stations, and numerical modelling. Both aircraft flew out of Rovaniemi in Finland. The Geophysica was equipped with a payload designed to probe the chemistry and microphysics of polar stratospheric clouds (PSCs) at -- or, with less precision, above -- the aircraft altitude. Prior to the flight campaign, Geophysica flew in a test campaign in Pratica di Mare - Italy.
The Miniature Airborne Udar (MAL) has been developed as compact automated instrument for measurement of the backscatter signal at two polarisations - one parallel to the laser polarisation and the other perpendicular to it. The position for MAL is behind the pilot ensuring eye-safety, and it looks in the zenith direction. In the instrumental complex of 'Geophysika', the task of MAL is to perform measurements of the backscatter signal and the depolarisation ratio of the backscatter light - in the near IR spectral region (850nm) -from 30 m till about 300 m above the aircraft. The work included both comparisons and correlation with the other in situ instruments for aerosol and trace gases. The instrument MAL is developed in co-operation by the Observatory of Neuchâtel and the Space Research Institute of the RAS - Moscow.
During the two flight campaigns with total of 11 flights in Pratica di Mare and Rovaniemi, the lidar instrument MAL showed an excellent reliability and stability of operation. The instrument was operational always when both the on-board computer was operational and when it itself was powered from the aircraft electrical power supply.
The absence of PSC close above to the M-55 flight altitudes determined the shift in the priorities and the data processing procedure, i.e., processing the MAL data for evidences of variation of the background aerosol layer and in the aerosol depolarisation ratio. This shift of the priorities was also valid for all in situ instruments. In absence of clouds MAL was used with integration of the successive range bins close to the aircraft into one, that is in backscatter sonde mode, with outputs: the variation of the total backscatter and the variation of the
depolarisation ratio. These output data have been formatted in a way to be compared to the data from FSSP-300 (Forward Scattering Spectrometer Probe -300), namely the aerosol particles number density. Such comparison was carried out for the several flights.
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