MJO不同活动中心位置对云南冬半年降水过程的影响  

Influence of MJO Center Position on Precipitation Process of Yunnan in Winter Half Year

作　　者：牛法宝[1] 杞明辉[1] 杨素雨[1] 琚建华[2] 

机构地区：[1]云南省气象台,昆明650034 [2]云南省气象局,昆明650034

出　　处：《气象》2013年第9期1145-1153,共9页Meteorological Monthly

基　　金：公益性行业(气象)科研专项(GYHY201306022);NSFC-云南省联合基金项目(U0833602和U1133603);气象关键技术集成与应用项目(CMAGJ2013M48)共同资助

摘　　要：通过对热带对流季节内振荡（MJO）的研究和业务实践应用表明，利用对MJO传播过程来研究延伸期（10～30d）天气已经成为一种新的、可行的手段。然而，在明确了MJO的活动位置条件下如何依据大气环流条件来把握云南冬季降水过程的延伸期预测，是预报实践中需要解决的重要问题。本文考虑云南冬半年在有北方冷空气南下入侵云南前提下，MJO活动位置（分为“干窗口”和“湿窗口”两种情况）及有无合适的水汽引导环流条件（分为“孟加拉湾一带90°E附近有南支槽系统”和“孟加拉湾至中南半岛西侧一带为反气旋环流”两种情况）主要有4种不同的配置类型，选取MJO影响下前3种不同配置类型的天气过程进行对比分析，期望能为云南冬半年延伸期天气预测过程中较好地把握过程降水及降水强度提供理论依据。分析表明：MJO活动中心进入孟加拉湾及西太平洋热带地区（本文称之为MJO“湿窗口”）以后将会充分激发这些地区的对流活动，MJO活动中心在孟加拉湾及西太平洋热带以外地区（本文称之为MJO“干窗口”）时不能充分激发云南上游热带地区的对流活动。在有北方南下冷空气影响云南的背景情况下，MJO在“湿窗口”时，要使云南出现大范围的降水天气过程必须还要有合适的环流条件（90°E附近南支槽前或西太平洋副热带高压西侧的偏南气流）引导热带地区的水汽进入云南；MJO在“干窗口”时，即便有合适的水汽输送与扰动环流条件，仍然不能造成云南大范围的降水天气过程。由于MJO在激发水汽方面的贡献非常明显，利用MJO的东传规律可以有效地进行云南冬半年降水的延伸期天气预测，并对中短期天气预报业务起到很好的指导作用。The research of MJO has showed that it is a new and workable method for studying the extend- ed-period weather forecast （10 to 30 days） to use the propagation process of MJO. However, how to pre- dict the extended-period rainfall process in winter Yunnan is an important problem to be solved in forecast operations. In this paper, rainfall circulation configurations under the influence of MJO are divided into three types, and the corresponding three weather processes are contrasted and analyzed in order to find the forecast predictors for the extended-period weather forecast. The results showed that firstly, the tropicalconvection activities will be fully aroused when MJO activity center enters into the west Bengal and tropical regions of Pacific （called ＂wet window＂）. Otherwise, the tropical convection activity is not active in the upstream region of Yunnan （called ＂dry window＂）. Secondly, when MJO is in wet window, the occur- rence of precipitation process is under the condition of cold air and suitable circulation. Southerly winds of Southern branch trough or the West Pacific subtropical high guides the water vapor into Yunnan. But, when MJO is in dry window, even though there is befitting condition of water vapor and circulation pertur bation, the large-scale rainfall process does not happen.

关 键 词：MJO 干湿窗口 云南 冬半年 降水过程 

分 类 号：P461[天文地球—大气科学及气象学]