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2022年4-6月云南异常低温事件的低频特征及成因

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利用NCEP/NCAR逐日再分析资料和云南省124个气象站观测资料,首先分析了 2022年4-6月云南异常低温事件的极端性及低频振荡变化特征,然后分析了对流层中层和低层大气环流系统低频振荡配置的演变特征.结果表明:1)2022年云南春末夏初(4-6月)出现了气候变暖背景下罕见的极端异常低温事件.平均气温为1961年以来历史同期第5低,1991年以来最低年,全省有42个气象站平均气温达到或突破历史同期最低纪录.2)云南2022年春末夏初的平均气温存在10～20 d显著性周期,方差贡献为45.7％,与实际强降温过程对应关系较好.3)云南10～20 d低频振荡气温降低最大位相7(升高最大位相3),500 hPa上云南被南压的贝加尔湖低频异常高压(低压)与日本海低频异常低压(高压)环流系统间的偏北(偏南)气流控制;700 hPa上中国东部到南海被低频偏北(南)气流控制,低频气温降温(升温)区与之对应,云南被偏东(西)气流控制,位于降温(升温)区;海平面气压场上西伯利亚冷高压增强南移,将高纬度冷空气带到低纬度地区,从而影响云南气温的变化,造成了云南强冷空气过程的形成和发展.因此,高低空低频环流系统配置和演变导致了 2022年4-6月云南异常低温事件.4)2022年4-6月,500 hPa上低频正异常高度扰动从高纬度向南传播到贝加尔湖附近,中低纬度低频正异常高度扰动从地中海附近向东移动到贝加尔湖一带,两支低频波列协同作用有利于我国东部和云南地区异常低温事件的产生、加强和维持.5)2022年春末夏初(4-6月),10～20 d低频振荡中,南支西风槽指数和西伯利亚高压指数分别超前云南低频气温7 d和5 d时达到最好的相关关系;这2个指数对云南异常低温过程预报具有很好的提前预示性.
Low-frequency characteristics and causes of the abnormally low tempera-ture event in Yunnan from April to June 2022
Based on NCEP/NCAR daily reanalysis data and observations from 124 meteorological stations in Yunnan Province,we analyze the extreme features and low-frequency oscillation characteristics of the abnormally low temperature event in Yunnan from April to June 2022.We also investigate the evolution of the spatial config-uration of low-frequency circulation systems in the middle and lower troposphere.The results are as follows:1)In the late spring and early summer(April-June)of 2022,Yunnan experienced a rare extreme low temperature event under the backdrop of climate warming.The average temperature was the fifth lowest on record for this period since 1961 and the lowest since 1991.Average temperatures at 42 stations reached or broke histori-cal records for the same period.2)There was a significant 10-20 d period for average temperatures in Yunnan in late spring and early summer of 2022,with a variance contribution of 45.7％.This 10-20 d oscillation was close-ly related to actual temperature drops.3)During the 10-20 d low-frequency oscillation,phase 7 corresponded to the maximum temperature decrease and phase 3 to the maximum temperature increase over Yunnan.At 500 hPa,Yunnan was influenced by northerly(southerly)airflow between a low-frequency anomalous high-pressure(low-pressure)system around Lake Baikal and a low-frequency anomalous low-pressure(high-pressure)system near the Sea of Japan in phase 7(phase 3).Simultaneously,the region from eastern China to the South China Sea was mainly controlled by low-frequency northward(southward)wind at 700 hPa,which correlated with cooling(warming)areas.Yunnan was mainly under control of the low-frequency easterly(westerly)air flow and also located in the cooling(warming)area.The sea level pressure field showed an enhanced and southward-moving Siberian high-pressure system,bringing cold air from high to low latitudes,affecting temperature changes in Yun-nan,and contributing to the strong cold air process.4)At 500 hPa,low-frequency positive height anomalies prop-agated southward from high latitudes to Lake Baikal,while low-frequency positive height anomalies at middle and low latitude moved eastward from Mediterranean Sea to Lake Baikal.The synergistic effect of these two low-fre-quency wave trains facilitated the generation,strengthening,and maintenance of abnormally low temperatures in eastern China and Yunnan from April to June 2022.5)In late spring and early summer of 2022,the South Branch Westerly Trough Index and the Siberian High Pressure Index in the 10-20 d low-frequency oscillation showed the best correlation with low-frequency temperatures in Yunnan at 7 and 5 d,respectively.These indices can effec-tively predict abnormal low-temperature processes in Yunnan.

Yunnanlate spring and early summer(April-June)of 2022abnormal low-temperature event10-20 d low-frequency oscillationcirculation system

陶云、郭萍、邢冬、周建琴、任菊章、陈艳、张万诚

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云南省气象科学研究所,云南 昆明 650034

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

云南省临沧市气象局,云南临沧 677099

云南省气候中心,云南 昆明 650034

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云南 2022年春末夏初(4-6月) 异常低温事件 10～20d低频振荡 环流系统

云南省重点研发计划-社会发展专项国家自然科学基金项目国家自然科学基金项目国家自然科学基金项目国家自然科学基金项目云南省基础研究计划基础研究专项中国气象局创新发展专项云南省气象局创新团队项目云南省气象局创新团队项目

202203 AC 10000642465004420306034216500441965005202401AT070124CXFZ2024J0452022CX032022CX04

2024

10.13878/j.cnki.dqkxxb.20240108001

大气科学学报
南京信息工程大学

大气科学学报

CSTPCD北大核心
影响因子：1.558
ISSN：1674-7097
年,卷(期)：2024.47(5)