近25年云南5月降水多寡的年代际异常特征及其成因  

Characteristics and causes of decadal anomalies in May precipitation in Yunnan over the past 25 years

作　　者：周建琴[1] 陶云 周杰 李蒙[1] 窦小东 ZHOU Jianqin;TAO Yun;ZHOU Jie;LI Meng;DOU Xiaodong(Yunnan Climate Centre/Yunnan Key Laboratory of Meteorological Disasters and Climate Resources in the Greater Mekong Subregion,Kunming 650034,China;Yunnan Institute of Meteorological Sciences/Research Center for Disastrous Weather in Hengduan Mountain and Low-latitude Plateau,CMA,Kunming 650034,China;Chongqing Climate Center,Chongqing 401147,China;Yunnan Meteorological Service Center,Kunming 650034,China)

机构地区：[1]云南省气候中心/云南省大湄公河次区域气象灾害与气候资源重点实验室,云南昆明650034 [2]云南省气象科学研究所/中国气象局横断山区低纬高原灾害性天气研究中心,云南昆明650034 [3]重庆市气候中心,重庆401147 [4]云南省气象服务中心,云南昆明650034

出　　处：《大气科学学报》2025年第2期267-277,共11页Transactions of Atmospheric Sciences

基　　金：国家自然科学基金项目(42165004);云南省重点研发计划项目(202203AC100005);中国气象局复盘总结专项(FPZJ2024-123);中国气象局创新专项(CXFZ2024J045);科技人才与平台计划项目(202405AC350093)。

摘　　要：近25年来云南5月降水年际变化特征减弱而年代际变化特征明显,在1999—2008年和2009—2023年发生了一次明显的由多转少的年代际变异,本文分析了这两个时段降水的持续异常特征及其环流成因。结果显示:1)1999—2008年和2009—2023年两个时段的全省性降水差异明显,平均的云南5月降水距平百分率分别为37.9%和-19.7%,且大部地区的降水量差值超过20 mm,其中中西部地区超过了60 mm。2)1999—2008年中高纬度环流有利于冷空气南下影响云南,阿拉伯海和孟加拉湾500 hPa高度场偏低,700 hPa风场为异常气旋环流,输送到云南境内的水汽偏多,降水偏多,而2009—2023年则与之相反。3)1999—2008年和2009—2023年两个时段环流差异明显的区域位于中低纬度。1999—2008年阿拉伯海季风和印缅槽同时偏强,云南5月降水主要受阿拉伯海季风强弱的影响。2009—2023年阿拉伯海季风和印缅槽偏强的时段不对应,同时西太平洋副热带高压偏强,其南侧的异常东风对来自印度洋的水汽输送有阻挡作用,其北侧的西风异常位于云南和华南一带,也不利于北方冷空气影响云南。4)利用欧拉方法计算的两个时段的云南水汽输送通量特征表明,1999—2008年5月60°E附近越赤道气流偏强,到达云南的印度洋暖湿水汽输送偏强,水汽辐合增强,而2009—2023年则与之相反。1999—2008年来自南(西)边界的水汽大(小)于2009—2023年;基于拉格朗日方法计算的700 hPa和500 hPa云南水汽输送轨迹特征显示,1999—2008年来自印度洋(西风带)的水汽输送轨迹数比2009—2023年分别偏多21%和25%(偏少2%和41%)。May precipitation plays a crucial role in the transition from the dry to the wet season in Yunnan,marking the onset of the region's rainy season.Understanding the mechanisms driving its anomalies has been a key focus and challenge in climate change research.Before the 1990s,May precipitation in Yunnan was primarily characterized by interannual variability.Therefore,meteorological studies predominantly examined precipitation anomalies in specific years.However,over the past 25 years,interannual variability has weakened,while interdecadal fluctuations have become more pronounced.A distinct shift from a wetter to drier phase occurred between the periods 1999-2008 and 2009-2023.This study analyzes the characteristics and underlying causes of these variations.The results indicate the following:1)The average precipitation anomaly percentage in May was 37.9%during 1999-2008 and-19.7%during 2009-2023.The precipitation difference between the two periods exceeded 20 mm across most regions and reached 60 mm in central and western Yunnan.These differences were statistically significant across most of the province.2)Atmospheric circulation patterns during 1999-2008(2009-2023)were(were not)conducive to the southward penetration of cold air into Yunnan.At 500 hPa,the Arabian Sea and Bay of Bengal exhibited low(high)geopotential heights,while at 700 hPa,anomalous cyclonic(anticyclonic)circulation prevailed.These conditions facilitated(hindered)more the transport of moisture into Yunnan,leading to increased(decreased)precipitation.3)The most pronounced circulation differences between the two periods occurred in the mid-and low-latitude regions.During 1999-2008,both the Arabian Sea monsoon and the Indo-Burma trough were strong,and May precipitation in Yunnan was primarily influenced by the intensity of the Arabian Sea monsoon.In contrast,during 2009-2023,the Arabian Sea monsoon did not coincide with the active phases of the Indo-Burma trough,while the western Pacific subtropical high was anomalously strong.The enhanced easterly wi

关 键 词：云南5月降水 年代际变化 大气环流机制 

分 类 号：P426.6[天文地球—大气科学及气象学]