摘要
This study investigates whether and how the Madden-Julian Oscillation(MJO)influences persistent extreme cold events(PECEs),a major type of natural disaster in boreal winter,over Northeast China.Significantly increased occurrence probabilities of PECEs over Northeast China are observed in phases 3 and 5 of the MJO,when MJOrelated convection is located over the eastern Indian Ocean and the western Pacific,respectively.Using the temperature tendency equation,it is found that the physical processes resulting in the cooling effects required for the occurrence of PECEs are distinct in the two phases of the MJO when MJO-related convection is consistently located over the warm pool area.The PECEs in phase 3 of the MJO mainly occur as a result of adiabatic cooling associated with ascending motion of the low-pressure anomaly over Northeast Asia.The cooling effect associated with phase 5 is stronger and longer than that in phase 3.The PECEs associated with phase 5 of the MJO are linked with the northwesterly cold advection of a cyclonic anomaly,which is part of the subtropical Rossby wave train induced by MJO-related convection in the tropical western Pacific.
本文利用高分辨率气温数据和热带季节内振荡(MJO)实时指数,研究了1979-2015年冬季MJO活动对中国东北持续性极端低温事件(PECE)的影响特征和机理.结果表明:当MJO对流分别位于暖池地区的东印度洋(位相3)和西太平洋(位相5)时,中国东北PECE的发生频率显著增加.利用温度方程诊断分析发现MJO两个位相所导致的冷却过程不同:当MJO处于位相3时,中国东北地区为低压异常,上升运动引起绝热冷却作用;而位相5所形成的气旋性环流为中国东北地区带来西北风冷平流,降温过程更强且持续更长时间.
作者
Yitian Qian
Pang-Chi Hsu
Huijun Wang
Mingkeng Duan
Yitian Qian;Pang-Chi Hsu;Huijun Wang;Mingkeng Duan(Key Laboratory of Meteorological Disaster,Ministry of Education,Nanjing University of Information Science&Technology,Nanjing 210044,China)
基金
supported by the National Natural Science Foundation of China[grant number 42088101]
the National Postdoctoral Program for Innovative Talent of China[grant number BX2021133]
the China Postdoctoral Science Foundation of No.70 General Fund[grant number 2021M701753]。
