同化FY3B/IRAS资料对GRAPES分析场影响诊断

GRAPES(Globe and Regional Assimilation and Prediction System)变分系统能够同化常规资料和非常规卫星资料,这些被同化的资料究竟对同化系统得到的分析场有何影响,目前国内外尚未见相关的研究文献。为此,首次采用基于信息熵信号自由度思想,诊断风云三号B星(FY3B)红外分光计(Infrared Atmospheric Sounder,IRAS)资料对GRAPES分析场的影响。诊断过程中,采用数值逼近方法,统计2012年12月24日18时到2013年1月22日00时共114个时次IRAS资料对GRAPES分析场影响,结果表明,IRAS中高层通道亮温资料对GRAPES分析场影响比地表通道20观测亮温的影响大,地表通道8和9观测亮温对分析场影响较大。前24个GRAPES变分同化时次每个时次IRAS通道亮温对分析场影响的贡献率分析结果显示,高层通道和H_2O通道贡献率较大。个例分析结果表明,在同化探空资料基础上加入IRAS资料后,温度和湿度增量场变化幅度较大,表明IRAS资料对分析场有降温和增湿作用。

Diagnosis Effect of Assimilating FY3B/IRAS Data on GRAPES Analysis Field

The variational system of Globe and Regional Assimilation and Prediction System (GRAPES) can assimilate the conventional and unconventional satellite data, but there are no relevant research literatures about the effect of assimilating these data on the analysis field of assimilation system at home and abroad. Therefore, we diagnose the effect of assimilation FY3B Infrared Atmospheric Sounder (IRAS) data on GRAPES analysis field based on information entropy and freedom degree of signal for the first time. In the process of diagnosis, the numerical approximation method is used. We study the effect of assimilation IRAS data (from 18 UTC, 24th Dec, 2012 to 00 UTC, 22th Jan, 2013, a total of 114 times) on GRAPES analysis field, and the results show that: the IRAS high channel brightness temperature data have greater influence on GRAPES field than the surface channel 20, while the surface channel 8 and 9 brightness temperature have greater influence than other channels on analysis field. The each time analysis results about contribution rate of the IRAS channel brightness temperature in the first 24 GRAPES variational assimilation times show that: the contribution rates of top channel and H2O channel are high. Results from case analysis show that after adding IRAS data based on radiosonde data assimilation, the temperature and humidity increment field change greatly, which indicates that the IRAS data have cooling and humidification effect on analysis field.