胡娅敏,翟盘茂,罗晓玲,吕俊梅,覃志年,郝全成. 2014. 2013年华南前汛期持续性强降水的大尺度环流与低频信号特征[J]. 气象学报, 72(3):465-477, doi:10.11676/qxxb2014.042
2013年华南前汛期持续性强降水的大尺度环流与低频信号特征
Large scale circulation and low frequency signal characteristics for the persistent extreme precipitation in the first rainy season over South China in 2013
投稿时间:2013-07-30  修订日期:2014-03-10
DOI:10.11676/qxxb2014.042
中文关键词:  华南前汛期  持续性强降水  季节内振荡  大尺度环流
英文关键词:The first rainy season over South China  Persistent extreme precipitation  Intraseasonal oscillation  Large scale circulation
基金项目:国家重点基础研究发展计划(973计划)项目(2012CB417205、2013CB430202)、国家自然科学基金项目(40905043、41375091)、中国气象局气候变化专项(CCSF201307)。
作者单位
胡娅敏 广东省气候中心, 广州, 510080
中国气象科学研究院灾害天气国家重点实验室, 北京, 100081 
翟盘茂 中国气象科学研究院灾害天气国家重点实验室, 北京, 100081 
罗晓玲 广东省气候中心, 广州, 510080 
吕俊梅 中国气象科学研究院灾害天气国家重点实验室, 北京, 100081 
覃志年 广西自治区气候中心, 南宁, 530022 
郝全成 广东省气候中心, 广州, 510080 
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中文摘要:
      自2013年3月下旬开始,华南地区遭遇持续性强降水袭击。采用小波分析、交叉小波变换和小波相干、集合经验模态分解(EEMD)、带通滤波等统计方法,分析2013年华南前汛期持续性强降水过程的大尺度大气环流和低频特征,寻找影响持续性强降水可能的前期信号。揭示出:(1)2013年华南前汛期持续性强降水主要分为两个时段:3月26日—4月11日(第1阶段)和4月23日—5月30日(第2阶段)。前者华南雨带呈现西北—东南分布,由北向南降水量逐渐增大,后者降水强度较前者强,雨带主要集中在华南北部和东南沿海地区。(2)第1阶段华南降水主要受北方冷空气的持续影响,第2阶段主要受西太平洋副热带高压和南海季风的影响。两个阶段的环流特征明显不同:第1阶段在对流层中层主要对应西高东低的经向环流,东亚大槽深厚、东北冷涡长时间盘踞,北方冷空气与来自西太平洋副热带高压西北侧的暖湿气流交汇在华南,此时以冷式锋面降水为主;第2阶段500 hPa高度场为两脊一槽的分布型,热带对流活跃,其上空表现一异常的气旋环流,具有季风降水的性质。(3)第1(2)阶段降水呈现出20—50 (8—15) d的振荡特征,可能是北方冷空气活动频繁(西太平洋副热带高压加强和南海季风爆发)的影响,交叉小波功率谱分析得到,东北冷涡(南海北部水汽输送的纬向分量)可能提前1(1/2)个周期,对华南降水具有一定的指示。
英文摘要:
      From April to June, widespread severe rainstorms events mainly concentrate over South China (SC). During the period, the persistent extreme precipitation events (PEPEs) are in high incidence and rainfall during this period accounts for nearly 40%-50% of the annual total. It is usually called the first rainy season (FiRS) over SC. From late March to mid-June in 2013, the precipitation frequently occurred in SC with multiple precipitation processes, severe intensity and long duration. Based on the statistical methods such as the wavelet analysis, the cross wavelet transform, the wavelet coherence, the ensemble empirical mode decomposition (EEMD) and the band pass filter, the PEPEs are analyzed. The results show that two persistent extreme precipitation processes occurred during the period of 26 March-11 April (which is called the first stage hereafter) and 23 April-30 May (which is called the second stage hereafter), respectively. During the first stage, rainfall amount increased from the north to the south region and accounted for 24.7% of the rainfall in FiRS with rainbelt extending from the southeast to northwest. However, during the second one, the precipitation intensity was stronger than that in the former and the amount reached 54.0% with rainbelt over the north and southeast coast region in SC. There are the predominant factors played an important role in the two persistent extreme precipitation processes. In the first stage, precipitation was continuously influenced by cold airflow from the north. In the latter, however, it was mainly affected by the tropical convection system from the south. Moreover, two PEPEs have been affected by the different large-scale atmosphere circulations. For the former one, the meridional circulation pattern with the high/low value system in the eastern/western region presented in the middle troposphere. A cold vortex continuously maintained over Northeast China, and the cold surge merged with the warm current from the northwest flank of the West Pacific Subtropical High (WPSH). It suggested that, the cold frontal precipitations hold a leading post in the first stage. Nevertheless, in the second one, the meridional circulation is rectified into the pattern with one trough between double ridges in the 500 hPa geopotential height. Before the monsoon breakout over the South China Sea (SCS), precipitation was still controlled by the cold front. There existed a duration transition between the first and the second stages. From perspective of precipitation low frequency feature, it transited from the intraseasonal oscillation into the quasi-biweekly one. After the monsoon breakout, the cold air decreased in severity. The WPSH has retreated from the SCS and the water vapor passage from the Bay of Bengal (BOB) established. In the meantime, the convection systems began active in the low latitudes. The troughs over the south branch were more active from the Indo-China Peninsula to SC. At the moment, an anomaly cyclonic circulation presented over the SC region. The warm convective precipitation occurred more often under the unsteady stratified atmosphere with remarkable convective activity developing in the second stage. Low frequency oscillation characteristics of precipitation and their predominant factors are further analyzed. Precipitation in the first stage showed a 20-50 d low frequency oscillation, which was affected by the active cold surge from the north region. In the second stage, it showed a 8-15 d low frequency oscillation, which was impacted by the strengthened WPSH and the SCS monsoon onset from the south. By using of the cross wavelet transform, the cold vortex over Northeast China and the zonal component of water vapor transportation over SCS are likely able to be used as possible early signals for the FiRS precipitation over the SC region for the extended range forecast.
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