Major advances foreseen in humidity profiling from the Water apour Lidar Experiment in Space (WALES)
Gérard, E. ; Tan, D.- G.- H. ; Garand, L. ; Wulfmeyer, V. ; Ehret, G. ; Di Girolamo, P.
Année de publication
2004
The need for an absolute standard for water vapor observations, in the <br>form of a global dataset with high accuracy and good spatial resolution,<br> has long been recognized. The European Space Agency's Water Vapour <br>Lidar Experiment in Space (WALES) mission aims to meet this need by <br>providing high-quality water vapor profiles, globally and with good <br>vertical resolution, using a differential absorption lidar (DIAL) system<br> in a low earth-orbit satellite. WALES will be the first active system <br>to measure humidity from space routinely. With launch envisaged in the <br>20082010 time frame and a minimum duration of two years, the primary <br>mission goals are to (a) contribute to scientific research and (b) <br>demonstrate the feasibility of longer-term operational missions. This <br>paper assesses the benefits of the anticipated data to NWP through <br>quantitative analysis of information content. Good vertical resolution <br>and low random errors are shown to give substantial improvements in <br>analysis error in one-dimensional variational data assimilation (1DVAR) <br>comparisons with advanced infrared sounders. In addition, the vertical <br>extent of the profiles is shown to reach 16.5 km or <img src="http://journals.ametsoc.org/na101/home/literatum/publisher/ams/journals/entities/223C.gif" alt="" class="entityA" align="bottom">100<br> hPa, well above the limit of radiance assimilation (13 km or 200 hPa). <br>Also highlighted are important applications in atmospheric sciences and <br>climate research that would benefit from the low bias promised by <br>spaceborne DIAL data and their complemen-tarity to other types of <br>humidity observations.</div>
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