LIDAR-MEASURED WINDS FROM SPACE - A KEY COMPONENT FOR WEATHER AND CLIMATE PREDICTION

The deployment of a space-based Doppler lidar would provide informatio n that is fundamental to advancing the understanding and prediction of weather and climate. This paper reviews the concepts of wind measurem ent by Doppler lidar, highlights the results of some observing system simulation experiments with lidar winds, and discusses the important a dvances in earth system science anticipated with lidar winds. Observin g system simulation experiments, conducted using two different general circulation models, have shown 1) that there is a significant improve ment in the forecast accuracy over the Southern Hemisphere and tropica l oceans resulting from the assimilation of simulated satellite wind d ata, and 2) that wind data are significantly more effective than tempe rature or moisture data in controlling analysis error. Because accurat e wind observations are currently almost entirely unavailable for the vast majority of tropical cyclones worldwide, lidar winds have the pot ential to substantially improve tropical cyclone forecasts. Similarly, to improve water vapor flux divergence calculations, a direct measure of the ageostrophic wind is needed since the present level of uncerta inty cannot be reduced with better temperature and moisture soundings alone.