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广西冬季降水的低频特征及其与MJO的联系
何洁琳, 陆虹, 何慧, 李艳兰, 周秀华
广西壮族自治区气候中心,广西 南宁 537000
摘要:
应用广西壮族自治区国家气象站降水,NCEP/NCAR逐日再分析资料,NOAA逐日向外长波辐射(OLR)等逐日资料,NOAA-CPC热带大气季节内振荡(MJO)指数等,使用经验正交函数分解方法分析了广西冬季降水的气候特征;用功率谱、带通滤波、相关分析和滞后线性回归等方法,以及定义MJO相关降水事件,研究了广西冬季降水异常偏多年的降水低频特征及其与MJO的联系。(1) 广西冬季降水特征以全区一致型分布为主;冬季降水异常偏多年份的逐日降水具有14~26 d的低频周期。(2) MJO强对流在赤道印度洋东部发展并东传到西太平洋热带地区时,广西可出现冬季持续强降水。(3) 当MJO异常对流在印度洋东部热带地区产生,中南半岛地区到华南地区上空为异常低频偏南和偏西南气流,有利于降水形成;当印度洋东部热带地区为MJO对流抑制区,华南地区上空为异常低频偏东气流控制,不利于降水产生。(4) 华南地区上空大气环流的异常是由热带印度洋地区的MJO对流激发的Rossby波列造成。
关键词:  热带大气季节内振荡  冬季降水  Rossby波  华南  延伸期预测
DOI:10.16032/j.issn.1004-4965.2019.028
分类号:
基金项目:
LOW FREQUENCY CHARACTERISTICS OF WINTERTIME RAINFALL IN GUANGXI AND ITS RELATIONSHIP WITH MJO
HE Jie-lin, LU hong, HE Hui, LI Yan-lan, ZHOU Xiu-hua
Guangxi Climate Center, Nanning 530022, China
Abstract:
Using daily precipitation records in Guangxi, NCEP/NCAR reanalysis dataset, outgoing long wave radiation (OLR) data, and the Madden-Julian Oscillation (MJO) index provided by NOAA-CPC, the climatic characteristics of wintertime rainfall in Guangxi are found through empirical orthogonal function analysis. By means of power spectrum analysis, bandpass filter, correlation analysis and lagged linear regression techniques, as well as the definition of the MJO-related rainfall events, the low-frequency features of wintertime rainfall and its connection with MJO are studied. The results are shown as follows. The chief distribution pattern of wintertime rainfall in Guangxi is uniform, with a 14~26 d low-frequency oscillation during the wintertimes with more precipitation. When the MJO convection develops in the eastern equatorial India Ocean and spreads to the tropical western Pacific, it would be a persistent rainfall period in wintertime. When the MJO anomalous convection occurs in the eastern tropical region of the India Ocean, the abnormal low-frequency south-west flow covers the Indochina Peninsula and southern China, which is beneficial to the formation of precipitation. On the contrary, when the MJO convection is suppressed over the tropical eastern India Ocean, the anomalous low-frequency easterly flow covers the southern China area, which is not favorable for rain. The anomalous atmospheric circulation over the south of China is caused by the Rossby wave train excited by the MJO convection in the tropical India Ocean region.
Key words:  tropical atmospheric seasonal oscillation  winter precipitation  Rossby wave, south of China  extended-range forecast
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