2007年夏季江淮强降水过程中10～30d低频变化及其与对流层上层波包活动的联系  

The 10—30-day intraseasonal oscillations of circulations and their associations with Rossby wave packets in the upper troposphere during persistent severe rainfall in summer 2007

作　　者：陈丹萍[1,2] 管兆勇[1] 侯俊[3] 奚子惠 

机构地区：[1]南京信息工程大学气象灾害省部共建教育部重点实验室,江苏南京210044 [2]中国气象科学研究院灾害天气国家重点实验室,北京100081 [3]江苏省气象局,江苏南京210008

出　　处：《大气科学学报》2016年第2期177-188,共12页Transactions of Atmospheric Sciences

基　　金：公益性行业(气象)科研专项(GYHY201406024);灾害天气国家重点实验室课题(2015LASW-A03)

摘　　要：利用NCEP/NCAR再分析和全国740站逐日降水资料,运用一点滞后相关等方法,对2007年夏季江淮流域强降水期间低频振荡的波动活动特征及其与降水低频变化的联系进行了分析。结果表明,在2007年夏季降水中,降水低频分量起着重要作用。降水的低频振荡主周期为10~30 d,降水距平时间序列与10~30 d低频分量具有较好的对应关系。低频扰动在对流层上层和低层都呈现波列状分布,且在降水活跃位相时,低频环流在高、低层具有斜压结构。在对流层上层,低频扰动有缓慢的东移倾向,相速度为每天2~3个经度。西风带中存在多次移动性波列向下游的传播,且在120°E以西以每天14经度的群速度向下游频散能量,表明10~30 d低频波动具有明显的下游发展特征。在强降水开始5 d前,低频波动与能量可起源于高纬的乌拉尔山附近,沿着西北—东南向的路径向下游传播。下游发展的低频波动为江淮流域带来了能量,为强降水的发生提供了条件。这些结果加深了人们对低频波动在江淮流域强降水过程中所起作用的认识,可为寻找江淮流域强降水过程预报线索提供科学依据。The characteristics of low-frequency oscillation during heavy rainfall in the Yangtze-Huaihe River valley（ YHRV） in summer 2007 and their relationships with Rossby wave packets in the midlatitudes were investigated in the present studyusing NCEP / NCAR reanalysis data along with precipitation data from 740 weather stations in China. Based on other studies,300 h Pa meridional wind variations were chosen to facilitate the analysis of the characteristics of the wave packets. Wave packet envelopes were also defined by performing Hilbert demodulation on the wind data. The relationship between wave packets and precipitation is mainly illustrated using time-lagged one-point correlation maps produced for v ＇（ the wind disturbance of 10—30 d filtering after deducting the seasonal average value of the meridional） and wave packet envelopes. The results demonstrate that the total precipitation was more than 800 mm in summer 2007,and the low-frequency component of precipitation playedan important rolein precipitation disturbances. The intraseasonal variation of precipitation wasmainly dominated by 10—30-day oscillation. The time series of the 10—30-day precipitation component wassignificantly and strongly correlated with the daily rainfall anomaly,with correlation coefficient of 0. 44. Eight phases were defined for describing the10—30-day low-frequency oscillation of circulation. It was found that most regions in the YHRV were affected by the southwest warm air of the northwest side of the anticyclone near the southeast coastal area of China's Mainland in the active precipitation phase in the lower troposphere（ 850 h Pa）,which was able to provide adequate water vapor for heavy rainfall events. On the other hand,it was found that there was a strong low-frequency anticyclone in the upper troposphere（ 200 h Pa）,with vigorous upward movement at 500 h Pa,which was also favorable for the precipitation. The circulation variations with 10—30-day periods were baroclinic in the vertical direction over East C

关 键 词：江淮流域 强降水过程 10~30 d振荡 Rossby波包 

分 类 号：P426.6[天文地球—大气科学及气象学]