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MJO对北半球高纬地区冬季地表气温的影响
崔静, 杨双艳, 李天明
(南京信息工程大学气象灾害教育部重点实验室/气候与环境变化国际合作联合实验室/气象灾害预报预警与评估协同创新中心)
The Influence of the Madden-Julian Oscillation on High-latitude Surface Air Temperature during Boreal winter
CUI Jing, YANG Shuangyan, LI Tim
(Key Laboratory of Meteorological Disaster,Ministry of Education KLME/ Joint International Research Laboratory of Climate and Environment Change ILCEC/ Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disaster CIC-FEMD,Nanjing University of Information Science Technology)
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投稿时间:2019-08-20    修订日期:2020-07-10
中文摘要: 基于1979-2016年的NCEP-NCAR逐日再分析资料研究了热带季节内振荡(MJO)对北半球冬季高纬地区地表气温(SAT)的影响。利用实时多变量MJO(RMM)指数,将MJO分为8个位相,其中位相2(6)对应于位于印度洋地区的正(负)对流。不同MJO位相下的SAT合成结果显示在MJO对流出现于位相2后的5-15天,北半球高纬地区(180°-60°W,60°-90°N)有明显的负SAT异常;由于热带异常加热信号的改变,在MJO对流出现在位相6后的5-15天该地区则对应于显著的正SAT异常。该地区温度的垂直结构在各个位相下也表现出类似的分布特征。500 hPa位势高度场的合成结果显示,在温度负(正)异常的位相对应有明显的位势高度负(正)异常,这种位势高度异常主要是由与热带对流异常相联系的向东北方向传播的罗斯贝波列所引起的。通过对波活动通量的计算,推断该东北方向传播的罗斯贝波列很可能是罗斯贝波能量频散的结果。700 hPa比湿场的合成结果表明在SAT负(正)异常的位相主要表现为负(正)的比湿异常,考虑到对流层中层的比湿与向下长波辐射之间存在着正相关关系,说明该温度异常也与辐射过程相关。上述分析表明与MJO相关的异常SAT信号可能来自平流输送和辐射过程。准确把握MJO位相与SAT异常信号的联系也可以为北半球高纬地区SAT的延伸期预报提供一些可靠线索。
Abstract:The impact of the Madden-Julian Oscillation (MJO) on the high-latitude wintertime surface air temperature (SAT) is examined based on NCEP-NCAR reanalysis daily data during 1979-2016. The real-time multivariate MJO (RMM) index, which divides the MJO into eight phases, where phase 2 (phase 6) corresponds to the enhanced (reduced) convection over the Indian Ocean and Maritime Continent, is used. A significant positive SAT anomaly over northern high-latitude region of (180, 60) is found 5-15 days following MJO phase 2, while a negative SAT anomaly appears over the same region about 5-15 days after the MJO is detected in phase 6, as the tropical forcing changes sign. An analysis of the lagging composite of the geopotential height at 500 hPa indicates that the Arctic SAT anomaly is a result of a north-eastward propagating Rossby wave train associated with the tropical convection anomaly of the MJO. An analysis of the wave activity flux indicates that the north-eastward propagating wave train is likely a result of Rossby energy propagation. A composite analysis of the specific humidity at 700 hPa shows that cool (warm) surface temperatures occur under dry (moist) air, due to the positive relationship between mid-troposphere specific humidity and downward longwave radiation. These composite fields suggest SAT signals due to the MJO result from both advective and radiative process. Hence, the MJO phases provide useful information for the extended-range forecast of high-latitude surface air temperature during boreal winter.
文章编号:201908200312     中图分类号:P461    文献标志码:
基金项目:国家自然科学基金项目(面上项目,重点项目,重大项目)
引用文本:
崔静,杨双艳,李天明,.[en_title][J].Meteor Mon,():-.
CUI Jing,YANG Shuangyan,LI Tim,.The Influence of the Madden-Julian Oscillation on High-latitude Surface Air Temperature during Boreal winter[J].Meteor Mon,():-.