Abstract
KNMI has had a long involvement with the recently launched Aeolus mission. Aeolus is an ESA Earth-Explorer mission and embarks the Atmospheric Laser Doppler Instrument (ALADIN). ALADIN is the first space-borne Doppler Wind Lidar (DWL) and was successfully launched in late August 2018. KNMI has had a long association with this mission and is sharing the software development of the L2B processor used to generate L2B wind products at ECMWF, develops related scene classification algorithms and performs calibration/validation activities. In addition, KNMI conducts more fundamental work for improving the retrieval of atmosphere optical properties, taking into account multiple scattering effects.
Highlights
Atmospheric Laser Doppler Instrument (ALADIN) is a high spectral resolution Doppler lidar operating at 355 nm mounted on the Aeolus satellite
As part of the ESA Aeolus DISC project, KNMI Scene classification is an important component of is leading the development of the so-called chain- the Level-2B wind processor (L2Bp)
The result is a binary map, and shared within the Aeolus Cal/Val team. It is denoted feature mask, used in the L2Bp used for end-to-end sensitivity tests in the wind classification procedure as input for the processing chain and accumulates new calibration accumulation of Mie and Rayleigh signals from settings, algorithm and tool development and measurement (2.88 km along track) to observation product monitoring and evolution
Summary
ALADIN is a high spectral resolution Doppler lidar operating at 355 nm mounted on the Aeolus satellite. The Mie channel uses a Fizeau interferometer coupled to an ACCD array to spectrally resolve and enable the separation of the spectrally narrow elastic backscatter (Mie) peak from clouds/aerosol and the spectrally broader return from atmospheric molecules. By measuring the spectral position of the Mie peak, the Doppler shift relative to the emitted signal frequency can be estimated and the line-of-sight velocity of the cloud/aerosol particles deduced. About 20% of the atmospheric samples have, in general, a cloud/aerosol return of sufficient signal-to-noise ratio to retrieve accurate winds, depending on the vertical sampling strategy. The two resulting subchannels are offset spectrally either side of the center frequency such that the spectrally broad Doppler shift of the atmospheric backscatter can be deduced using the ratio of the two branches of the Rayleigh channel returns. Cloud and aerosol optical properties are being produced with a horizontal resolution down to 3 km, the basic Aeolus horizontal integration length, as secondary product
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