大气科学学报2025，Vol.48Issue(2)：267-277,11.DOI:10.13878/j.cnki.dqkxxb.20240111001
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
摘要
Abstract
May precipitation plays a crucial role in the transition from the dry to the wet season in Yunnan,mark-ing the onset of the region's rainy season.Understanding the mechanisms driving its anomalies has been a key fo-cus and challenge in climate change research.Before the 1990s,May precipitation in Yunnan was primarily char-acterized by interannual variability.Therefore,meteorological studies predominantly examined precipitation anom-alies 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 pe-riods 1999-2008 and 2009-2023.This study analyzes the characteristics and underlying causes of these varia-tions. The results indicate the following:1)The average precipitation anomaly percentage in May was 37.9％dur-ing 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 Ara-bian Sea monsoon.In contrast,during 2009-2023,the Arabian Sea monsoon did not coincide with the active pha-ses of the Indo-Burma trough,while the western Pacific subtropical high was anomalously strong.The enhanced easterly winds along its southern flank obstructed moisture transport from the Indian Ocean,while the strengthened westerly winds on its northern side extended over Yunnan and South China,suppressing the intrusion of cold air.4)Water vapor transport flux characteristics were analyzed using both Eulerian and Lagrangian meth-ods.Eulerian analysis revealed moisture flux convergence over Yunnan in May during 1999-2008 but divergence during 2009-2023.The influx of moisture from Yunnan's southwestern border was greater during 1999-2008 than in 2009-2023,while moisture flux from the western border was smaller during 1999-2008 than in 2009-2023.Lagrangian tracking of moisture transport pathways at 700 hPa and 500 hPa showed that the number of wa-ter vapor transport trajectories originating from the Indian Ocean was 21％and 25％higher during 1999-2008 than in 2009-2023,respectively.In contrast,the proportion of moisture transport from the westerlies was 2％and 41％lower during 1999-2008 compared to 2009-2023. The findings of this study indicate that the persistent May precipitation anomalies in Yunnan over the past 25 years have been closely linked to variations in moisture transport from the Indian Ocean.The interdecadal differ-ences in precipitation during 1999-2008 and 2009-2023 can largely be attributed to shifts in Indian Ocean moisture.However,these decadal-scale variations may also be influenced by external forcing factors,such as sea surface temperature anomalies.The relationship between May precipitation in Yunnan and sea surface temperature anomalies remains a critical avenue for future research.关键词
云南5月降水/年代际变化/大气环流机制Key words
May precipitation in Yunnan/interdecadal variation/atmospheric circulation mechanisms引用本文复制引用
周建琴,陶云,周杰,李蒙,窦小东..近25年云南5月降水多寡的年代际异常特征及其成因[J].大气科学学报,2025,48(2):267-277,11.基金项目
国家自然科学基金项目(42165004) （42165004）
云南省重点研发计划项目(202203AC100005) （202203AC100005）
中国气象局复盘总结专项(FPZJ2024-123) （FPZJ2024-123）
中国气象局创新专项(CXFZ2024J045) （CXFZ2024J045）
科技人才与平台计划项目(202405AC350093) （202405AC350093）
