Abstract

Tropospheric wind field is a primary atmospheric variable, the knowledge of which is required at a global scale for operational meteorology and climatology studies. With the present state-of-the-art technology a spaceborne Doppler coherent lidar is foreseen to fullfil the requirements on sampling and wind speed accuracy. An initial feasability study has been conducted at NOAA in the late 70's proposing a viable concept for a laser remote sensor instrument WINDSAT. In the late 80's NASA and ESA started two studies on wind Doppler lidar so-called LAWS and ALADIN respectively to be launched either on a polar or a low inclinaison orbit depending on the scientific objectives and instrument performances dictated by the overall technology : lidar and platform. In these two studies a conical scanning mode provides the horizontal coverage at the earth surface. In a separate way restricting at first the scientific objectives to the climatology of the tropics CNES in France started a feasability study for a low inclinaison mission so-called BEST which includes among others a wind Doppler lidar. A new instrumental concept is proposed for BEST which is a multi-fixed line-of-sight configuration relaxing the constraints on lag-angle compensation and laser technology. So, a comparison of the two scanning modes has to be made keeping in mind the applications in order to show what can be acomplished with an increasing instrumental complexity. The various subjects to be covered by a comparison analysis are : horizontal coverage, cloud obstruction, sampling at various time scales, representativeness and wind speed accuracy, but also the data assimilation methods. Such a study is conducted for BEST and ALADIN by LMD and DMN following a step by step approach with an increasing complexity and completeness.

© 1991 Optical Society of America