ABSTRACT

Due to the insufficiencies of conventional observations and the effectiveness of bias corrections, it is still necessary to assimilate data from polar orbit satellites into a limited-area rapidly updated multiscale analysis and prediction system for Central Asia (RMAPS-CA). This study diagnoses the observation errors of the radiation brightness temperature (BT) of satellite Microwave Humidity Sounder (MHS) from multiple platforms through comparisons to the simulated BTs by the Community Radiative Transfer Model (CRTM) with soundings and a GFS input separately. The results show that the majority BIAS of the MHS BT compared with the simulated BT falls within −1.5–2.0 K and increases with an increase in the peak energy contribution height (PECH). No significant bias differences for the same channel of MHS and the same satellite are found across the different sounding stations, but obvious differences are found for the same channel from different satellites. Additionally, most of the GFS BTs are higher than the MHS BTs, which increase with the PECH. Moreover, almost all PDF distributions of the observed MHS BT bias relative to the GFS BT form a nearly Gaussian distribution, with the centre value being positive for channels 3 and 4. An assessment of the initial applications of MHS to RMAPS-CA is then conducted through two one-month retrospective runs, and forecasts initialized from analyses with and without MHS are verified against the observations. The results show that compared to the natural run for which no observations are assimilated, an improvement in the geopotential height of approximately 55.3% can be obtained by the assimilation of MHS, along with improvements of 12.8%, 4.7% and 2.3% for temperature, specific humidity (SPFH), and wind speeds below 200 hPa, respectively, for an average RMSE with initial time, which is valued at 2.9% and 3.3% for the SPFH at 2 m and wind speed at 10 m, respectively In addition, significant improvements in 24-h precipitation of 11.3%, 28.7% and 20.0% are obtained for light, medium and heavy rain, respectively, while no positive effects are obtained for rainstorm forecasts.

摘要

由于常规观测的不足和偏差修正的有效性，仍需要将极轨卫星的数据同化成有限区域快速更新的中亚多尺度分析预测系统（RMAPS-CA）。本研究通过与社区辐射传递模型（CRTM）分别进行探测和GFS输入的模拟BTs进行比较，诊断出来自多个平台的卫星微波湿度测深仪（MHS）辐射亮温（BT）的观测误差。结果表明，与模拟 BT 相比，MHS BT 的大多数 BIAS 落在 -1.5-2.0 K 内，并且随着峰值能量贡献高度（PECH）的增加而增加。MHS 的同一频道和同一卫星在不同的探测站之间没有发现明显的偏差差异，但在不同卫星的同一频道上发现了明显的差异。此外，大多数 GFS BTs 高于 MHS BTs，随着 PECH 的增加而增加。此外，观察到的 MHS BT 偏差相对于 GFS BT 的几乎所有 PDF 分布都形成近乎高斯分布，通道 3 和 4 的中心值为正。 然后对 MHS 对 RMAPS-CA 的初始应用进行评估通过两个为期一个月的回顾性运行，并根据观察结果验证从有和没有 MHS 的分析中初始化的预测。结果表明，与没有同化观测值的自然运行相比，