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Abstract
Preparations for the European Space Agency's (ESA) Atmospheric Dynamics Mission (ADM-Aeolus), which is scheduled for launch in 2011, are in full progress. The direct detection high spectral resolution Doppler Wind Lidar (DWL) satellite instrument will be the first to measure wind profiles from space, from the surface up to 30 km altitude.
An important part of the preparations is to study the possibilities of calibrating the wind results by means of surface
reflections. To estimate the effect of water motion due to waves, a simple wave model has been combined with a reflectivity model of the water surface. This includes specular reflection on smooth water surfaces and Lambertian reflection on foam caused by wind streaks and breaking waves. The effect of sub-surface reflection is still being investigated. Using this model, the average net water movement that will be observed by the DWL instrument is estimated. It is concluded that, depending on local atmospheric conditions, a non-zero water movement may be observed, which leads to biases in the observed wind profile. Therefore, a zero wind calibration based on land surface reflections has been recommended to ESA. Land surface returns are now being further investigated.
Another part of the preparations includes the development of level 2B (i.e., wind) processing software (L2Bp). This software will accept as input measurement data files (level 1B) and uses an estimate of the atmospheric temperature and pressure profiles (from a numerical weather prediction model) to retrieve the wind profile from the spectrometer data. This software will be made available by ESA as source code, free of charge, to all interested users in the meteorological/research community, and may be used as standalone software, or integrated as subroutine in a larger system for use in scientific or operational applications. The working of the L2Bp will be illustrated at the conference.