青藏高原坡面观测信息对我国夏季降水预报的作用

The Role of Observations from Tibetan Plateau Slope in Summer Rainfall NWP in China

利用不同同化方式分别同化青藏高原地区新一代综合气象观测网的自动站和GPS大气可降水量信息,探讨这些观测资料对我国夏季不同区域降水预报的作用。通过两组数值试验对2008年夏季连续两个月的天气进行分析场和降水预报结果检验,得出以下主要结论:(1)由于同化测站的平均台站高度在2550m以上,因此同化青藏高原地区新一代综合气象观测网资料后,对背景场调整的正作用主要集中在500 hPa以上;循环同化方式对背景场的调整作用比静态同化方式更明显,尤其在500 hPa以上;(2)无论用静态同化,还是循环同化,该观测网资料对华北地区降水预报的改善作用都不太明显,只是对个别降水量级有改善作用;(3)采用静态同化,会对西南地区东部24小时降水预报有改善作用;在多数情况下同化沿99°E附近的7个测站资料得到的降水预报结果比同化24个站的好;(4)对于长江中下游地区,采用循环同化方式更有利于该地区降水预报准确率的提高,尤其是对25～48小时降水的预报;同时,在多数情况下同化24个自动站和GPS大气可降水量信息对降水预报改善比只同化7个站的更好。

Using different assimilation methods,data from automatic stations and precipitable water vapor （PWV） data from GPS stations in the Tibetan Plateau and its vicinity are assimilated,in order to investigate the role played by these observations in summer rainfall prediction in China.Through comparing assimilation results and precipitation forecast results of two months in summer of 2008,the main conclusions can be drawn from this paper as follows：Firstly,as the average height of these observational stations is above 2550 m,the positive effects to adjust the background fields are concentrated on the pressure above 500 hPa after assimilating the observations in the Tibetan Plateau and its vicinity;The adjustment using intermittent assimilation is more obvious than using single assimilation,especially above 500 hPa.Secondly, regardless of intermittent assimilation or single assimilation,the improvements of precipitation forecast in North China are less obvious,except for individual precipitation levels.Thirdly,using single assimilation can improve obviously the rainfall forecast in eastern Southwest China;In most cases,precipitation forecast results obtained by assimilating the 7 stations＇ observations along 99°E are more accurate than by assimilating the 24 stations＇ observations.Fourthly,using intermittent assimilation is more conductive to the precipitation forecast in the Yangtze River areas,especially for the 25-48 h precipitation forecast;At the same time,the precipitation forecast by assimilating 24 stations＇ observations is superior to the one by assimilating 7 stations＇ mostly.