Future Space-Based Coherent Doppler Wind Lidar for Global Wind Profile Observation

Global wind measurements are essential for numerical weather prediction (NWP), climate studies, and various meteorological studies. Current space-based passive sensors and micro sensors have large coverage and high temporal resolution but low vertical resolution. The Doppler Wind Llidar (DWL) is a useful technique for wind measurement. JAXA studies the feasibility of a future space-based coherent DWL (CDWL) for global wind profile observation. The mission concept of the space-based CDWL is designed to have one look for line-of-sight (LOS) wind measurement at an off-nadir angle of 35° at an azimuth angle of 90° (270°) along satellite track. The candidate altitude and orbit of the satellite are 300 km and dawn-dusk sun-synchronous polar orbit. The forecast impacts of both 1.5- and 2-µm space-based DWL were evaluated using the operational global data assimilation system. The data assimilation experiments were conducted in August in 2018 to assess overall impact and seasonal dependence. It is found that the two space-based DWL have positive impact on NWP. Relative forecast error reduction for 1.5- and 2-µm space-based DWLs can be expected to about 3 and 2%, respectively. Compared to the 2-µm DWL experiment, 1.5-µm DWL experiment had a feature that the number of data usage is larger in the lower layer and less in the upper layer. The future space-based CDWL will fill the gap of the current global wind observing systems and contribute to the improvement of the initial conditions for NWP, atmospheric dynamics and phenomena, and various meteorological researches.