COSMIC掩星资料在青藏高原地区的偏差特征  

The Characteristics of COSMIC Radio Occultation Data Biases over Qinghai-Tibetan Plateau

作　　者：余小嘉 杨胜朋 蒋熹[1,2] YU Xiaojia;YANG Shengpeng;JIANG Xi(Joint Center for Data Assimilation Research and Application,Nanjing University of InformationScience and Technology,Nanjing 210044,Jiangsu,China;College of Atmospheric Science,Nanjing University of Information Science and Technology,Nanjing 210044,Jiangsu,China)

机构地区：[1]南京信息工程大学资料同化研究与应用联合中心,江苏南京210044 [2]南京信息工程大学大气科学学院,江苏南京210044

出　　处：《高原气象》2019年第2期288-298,共11页Plateau Meteorology

基　　金：国家自然科学基金项目(91337218;41875032;41871053);公益性行业(气象)科研专项(GYHY201406008);江苏省"青蓝工程"项目

摘　　要：利用2007—2013年COSMIC(Constellation Observing System for Meteorology,Ionosphere,and Climate)掩星RO(Radio Occutaion)资料和欧洲中期天气预报中心ECM WF(European Centre for M ediumRange Weather Forecasts)分析资料,研究了COSM IC RO探测的大气折射率及其反演的温度和水汽在青藏高原及其周边地区的偏差特征。结果表明,在夏季和秋季,高原,西南季风区和东部平原地区,大气折射率在对流层里均存在系统性的正偏差,其中高原偏差最大,在夏季可达0. 7%。冬季和春季,大气折射率在青藏高原对流层中下部有小的正偏差,而在西南季风区和平原地区对流层中下部有明显的负偏差。温度和水汽是折射率的反演产品,折射率的正偏差对应着温度的负偏差和水汽的正偏差。因此夏季高原地区的温度和相对湿度偏差可达-0. 5℃和7%。同时,夏季在西南季风区对流层顶出现了11%的相对湿度偏差。对流层下层折射率的负偏差和低层大气多路径效应有关,折射率正偏差和大气中的云水有关。对流层顶附近的相对湿度偏差,则是由于ECMWF模式结果不精确所引入的。COSMIC(Constellation Observing System for Meteorology,Ionosphere,and Climate)RO(Radio Occutaion)data are collocated in space and time with ECMWF(European Centre for Medium-Range Weather Forecasts)analyses during 7 year period from 2007 to 2013 over Qinghai-Tibetan Plateau and its surrounding areas.Atmospheric refractivity,temperature and relative humidity derived from COSMIC GPS ROs are compared with those of the ECMWF analysis.It is found the COSMIC GPS RO refractivity observations are systematically greater than the refractivity calculated from ECMWF analyses in summer and autumn.The fractional refractivity bias over Qinghai-Tibetan Plateau is larger than that over southwest monsoon area and plain with the value of 0.7%.In winter and spring the refractivity bias over Qinghai-Tibetan Plateau is positive,while that over southwest monsoon area and plain is negative.Temperature and water vapor of GPS RO are derived from refractivity.The positive bias of refractivity is highly correlated with positive water vapor bias and negative temperature bias.The bias of relative humidity and temperature are 7%and 0.5℃,respectively over Qinghai-Tibetan Plateau.It is noted that relative humidity bias can reach 11%at the top of troposphere over southwest monsoon area.The lower tropospheric negative refractivity biases are related to the multi-path effect,and the positive biases in the middle and lower troposphere are the result of the influence of cloud.The occurrence of relative humidity bias near the tropopause is due to the inaccuracy of the ECMWF mode results.

关 键 词：青藏高原 GPS掩星 资料同化 折射率 

分 类 号：P405[天文地球—大气科学及气象学]