Development and Potential of Space-Borne Doppler Wind Lidar

The advantage of lidar over other wind sensors is presented in this paper. With more than 20 years research, the development of the space-borne wind lidar is reviewed. Longer-term investigation has made many technologies suitable for the wind lidar measurement from an orbital platform become mature. However, there are still some problems to be solved. In order to obtain the optimal performance in wind detection, great importance is being attached to the simulation of a virtual space-borne wind lidar system on computer as developed by NASA and ESA.

利用星载激光雷达资料研究东亚地区云垂直分布的统计特征

已有研究表明:云的垂直结构(简称CVS)是一个在卫星资料反演和气候模式预测中很重要的云特征。本文通过利用美国2006年刚发射的卫星CALIPSO(Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Obser-vations)所负载的激光雷达Level2_05km的云数据,研究了东亚地区(18°N^53°N,74°E^144°E)云的垂直分布特征。结果表明:东亚地区多层云云量在夏季、秋季、冬季、春季分别为43.6%、29.6%、21.1%、33.3%,而多层云分布中双层云比例最大。云顶和云底高度除了随季节变化显著外,还有明显的区域特征。单层云、双层云以及三层云的云顶和云底高度的数据显示,三层云中最上层的云顶和云底最高,并始终高于两层云中最上层云的云顶和云底高度。平均云层厚度季节变化不明显,其值普遍在0.9~2km范围之间。而云层间距同样没有明显的季节和区域变化,其出现的概率随距离的增大而减小。其中,间距在0.35km的概率最大,占到将近50%。而间距在1.45km附近的概率大约为15%,高一点的可达到20%。

Synergistic Use of AIRS and MODIS for Dust Top Height Retrieval over Land

It is nontrivial to extract the dust top height（DTH） accurately from passive instruments over land due to the complexity of the surface conditions. The Moderate Resolution Imaging Spectroradiometer（MODIS） deep blue（DB） algorithm can be used to infer the aerosol optical depth（AOD） over high-reflective surfaces. The Atmospheric Infrared Sounder（AIRS） can simultaneously obtain the DTH and optical depth information. This study focuses on the synergistic use of AIRS observations and MODIS DB results for improving the DTH by using a stable relationship between the AIRS infrared and MODIS DB AODs. A one-dimensional variational（1DVAR） algorithm is applied to extract the DTH from AIRS. Simulation experiments indicate that when the uncertainty of the dust optical depth decreases from 50% to 20%, the improvement of the DTH retrieval accuracy from AIRS reaches 200 m for most of the assumed dust conditions. For two cases over the Taklimakan Desert, the results are compared against Cloud-Aerosol Lidar with Orthogonal Polarization（CALIOP） measurements. The results confirm that the MODIS DB product could help extract the DTH over land from AIRS.

Evaluation of Cloud Top Height Retrievals from China’s Next-Generation Geostationary Meteorological Satellite FY-4A

To evaluate the validity of cloud top height (CTH) retrievals from FY-4A, the first of China's next-generation geostationary meteorological satellite series, the retrievals are compared to those from Himawari-8, CloudSat, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and Moderate Resolution Imaging Spectroradiometer (MODIS) operational products from August to October 2017. Regarding CTHs from CloudSat, CALIPSO, and MODIS as truth, the results show that the performance of FY-4A CTH retrievals is similar to that of Himawari-8. Both FY-4A and Himawari-8 retrieve reasonable CTH values for single-layer clouds, but perform poorly for multi-layer clouds. The mean bias error (MBE) shows that the mean value of FY-4A CTH retrievals is smaller than that of Himawari-8 for single-layer clouds but larger for multi-layer clouds. For ice crystal clouds, both FY-4A and Himawari-8 obtain the underestimated CTHs. However, there is a tendency for FY-4A and Himawari-8 to overestimate the CTH values of CloudSat and CALIPSO mainly for low level liquid water clouds. The temperature inversion near the tops of water clouds may result in an overestimation of CTHs. According to the MBE change with altitude, FY-4A and Himawari-8 overestimate the CTHs mainly for clouds below 3 km, and the overestimation is slightly more apparent in Himawari-8 data than that in FY-4A values. As the cloud optical thickness (COT) increases, the CTH bias of FY-4A CTH retrievals gradually decreases. Two typical cases are analyzed to illustrate the differences between different satellites' CTH retrievals in detail.

Estimation of the Aerosol Radiative Effect over the Tibetan Plateau Based on the Latest CALIPSO Product

Based on the CALIPSO （Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation） Version 4.10 products released on 8 November 2016, the Level 2 （L2） aerosol product over the Tibetan Plateau （TP） is evaluated and the aerosol radiative effect is also estimated in this study. As there are still some missing aerosol data points in the day-time CALIPSO Version 4.10 L2 product, this study re-calculated the aerosol extinction coefficient to explore the aer-osol radiative effect over the TP based on the CALIPSO Level 1 （L1） and CloudSat 2B-CLDCLASS-LIDAR products. The energy budget estimation obtained by using the AODs （aerosol optical depths） from calculated aerosol extinction coefficient as an input to a radiative transfer model shows better agreement with the Earth＇s Radiant En- ergy System （CERES） and CloudSat 2B-FLXHR-LIDAR observations than that with the input of AODs from aero- sol extinction coefficient from CALIPSO Version 4.10 L2 product. The radiative effect and heating rate of aerosols over the TP are further simulated by using the calculated aerosol extinction coefficient. The dust aerosols may heat the atmosphere by retaining the energy in the layer. The instantaneous heating rate can be as high as 5.5 K day^-1 de-pending on the density of the dust layers. Overall, the dust aerosols significantly affect the radiative energy budget and thermodynamic structure of the air over the TP, mainly by altering the shortwave radiation budget. The signific-ant influence of dust aerosols over the TP on the radiation budget may have important implications for investigating the atmospheric circulation and future regional and global climate.