A review of the technical system of spaceborne Doppler wind lidar and its assessment method

Spaceborne Doppler Wind Lidars (DWL) are powerful tools in global wind observations. The first spaceborne Doppler wind lidar designed by European Space Agency (ESA) was launched successfully in August 2018. Meanwhile, the US and Japan provide huge resources in the demonstration and development of new technical systems of spaceborne DWLs, which are Hybrid DWL (HDWL) and Coherent DWL (CDWL), respectively. The technical systems of Aeolus, HDWL, and CDWL were assessed from three aspects, including the data acquisition rate or measurement number, the accuracy of wind observations, and the role played in improving the Numerical Weather Prediction (NWP) results to provide reference for our country to develop our own spaceborne DWL. We introduced the three technical systems briefly because the three technical systems of spaceborne DWLs are relatively different. These technical systems were assessed from the three aspects using previous research results. The three technical systems, which consist of Aeolus, HDWL, and CDWL, were assessed through the data acquisition rate or measurement number. Previous studies illustrated that the profiles of measurements obtained by HDWL is twice as much that of CDWL, and four times as much that of Aeolus. The data acquisition rate of CDWL is low due to its coherent-detection technology. The three technical systems are also assessed through the accuracy of wind observations. The main factors, which affect the accuracy of wind observations, are Poisson noise and atmospheric heterogeneity. Previous studies demonstrated that wind observations obtained by coherent-detection technology or the Mie channel of Aeolus has high accuracy (about 0—2 m/s) and traced by aerosol or cloud particles. However, its observations only cover about 30% of the total observations. The accuracy of wind observations obtained by direct detection is relatively low (about 1—3 m/s) and traced by molecules. Its observations can cover about 70% of the total observations. Generally, the global wind distributions can be well detected by combining coherent and direct detection. Observing System Simulation Experiments (OSSEs) provide a quantitative evaluation of new observing systems for the improvement of NWP. ESA, the US, and Japan verified the positive impact of Aeolus, HDWL, and CDWL on NWP results through OSSEs. Studies also indicate that uniform spaceborne DWL profile coverage is more important than the observations of horizontal vector wind using joint observations with two Aeolus-type spaceborne DWLs. Meanwhile, the observations of horizontal vector wind perform better in the improvement of the forecast results close to the satellite tracks than the observations of line-of-sight wind observations. HDWL is expected to achieve more favorable improvement of NWP forecast due to its larger data coverage and ability to observe the horizontal vector wind. The conclusions are drawn based on previous studies. Furthermore, HDWL and CDWL are still on the demonstration phase. Their parameters may be justified in the future, affecting the accuracy of wind observations. Future research on the comparison of the technical systems of spaceborne DWLs should be developed. © 2022 National Remote Sensing Bulletin. All rights reserved.