我国南方冬季持续性温湿异常事件的分类和特征分析

发布时间：2018-03-24 06:34

本文选题：冷湿事件　切入点：中国冬季气候　出处：《中国气象科学研究院》2017年硕士论文

【摘要】：低温雨雪冰冻事件对人类活动和农业生产有很大影响,是我国南方地区冬季影响重大的气象灾害之一。本文将从我国南方地区温度和降水异常特征入手,分析各类持续性温湿异常事件影响系统之间的联系与差别。持续性异常事件具有天气和气候异常双重特征。本文主要利用1981-2010年中国2474站逐日气温和降水数据,通过多变量联合EOF客观地挑选我国南方地区冬季持续性温湿异常事件的易发区域,利用关键区各站逐日气温和降水异常序列,将我国南方冬季持续性异常事件分为冷湿、冷干、暖湿和暖干四类异常事件,并用NCEP-NCAR逐日再分析资料对各类持续性异常事件环流特征进行合成分析及对比。通过分析得出,欧亚大陆中高纬上空“北高南低”的异常环流形势使得温带急流减弱,副热带急流增强,有利于冷空气向南爆发,而中纬度地区“东高西低”的异常环流则对应西太平洋副高增强北移和南支西风槽的活跃,有利于偏南风水汽输送达到我国南方地区,因此降水偏多。两种异常环流型的配合,使得我国南方出现各种的持续性异常事件,冷湿事件(低温雨雪冰冻事件)正是在有利于降水和有利于降温的两种异常环流型连续影响下发生的。在此基础上,考虑冷湿事件与其他异常事件之间的不同,利用其发生期间存在差别变化的关键系统,分别定义描述我国南方地区冬季降温的“北高南低”指数()、降水的“东高西低”指数(),可以作为我国南方地区低温雨雪冰冻事件的前期环流信号,可提前至少一周左右对持续性事件做出预测,有助于提高我国南方地区冬季冷湿(低温雨雪冰冻)事件的预报能力。本文同时还对2016年1月我国南方地区的温湿特征进行了分析,结果显示,2016年1月20-25日,南方地区出现持续性异常冷干事件。“北高南低”指数提前8天转为正值,“东高西低”指数一直徘徊在0附近,直到提前4天转为负值,并稳定到事件结束,再一次表明了定义的环流指数可以作为南方持续性温湿异常事件的预报指标。进一步对北极增暖的原因及其对此次冷干的影响机理进行了分析,前期(2015年12月底)北美沿岸海温出现暖异常,激发出北美东岸至北欧的遥相关波列,引起的扰动风对平均温度梯度的向极输送,使得北极增暖。北极的迅速增温使极涡和极地冷空气向南移动,在中西伯利亚堆积后向南爆发,造成我国出现大范围降温。但同期由于水汽条件不好,没有出现持续性降水,故而我国南方地区为持续性异常冷干事件。
[Abstract]:The cold rain and snow freezing event has great influence on human activities and agricultural production, and is one of the major meteorological disasters in southern China in winter. This paper will start with the anomalous characteristics of temperature and precipitation in southern China. This paper analyzes the relationship and difference between the influence systems of various kinds of persistent temperature and humidity anomalies. The continuous abnormal events have the dual characteristics of weather and climate anomalies. The daily temperature and precipitation data of 2474 stations in China from 1981 to 2010 are mainly used in this paper. By using multivariable and EOF, the regions prone to winter persistent abnormal temperature and humidity events in southern China are selected objectively. By using the daily temperature and precipitation anomaly sequence of stations in key areas, the winter persistent abnormal events in southern China are divided into cold and wet, cold and dry winter events. The circulation characteristics of various persistent abnormal events are synthetically analyzed and compared with the NCEP-NCAR daily reanalysis data. The anomalous circulation of "north high south low" over the middle and high latitudes of Eurasia makes the temperate jet flow weaken and the subtropical jet increase, which is conducive to the onset of cold air to the south. The anomalous circulation of "East high and west low" in mid-latitude region corresponds to the northward shift of the subtropical high in the western Pacific Ocean and the activity of the westerly trough in the southern branch of the western Pacific Ocean, which is beneficial to the southward wind and vapor transport to the southern part of China, so there is more precipitation. There are various kinds of persistent abnormal events in southern China. The cold and wet events (low temperature rain and snow freezing events) occur under the continuous influence of two abnormal circulation patterns, which are favorable to precipitation and favorable to cooling. Taking into account the differences between cold and wet events and other abnormal events, and making use of the key systems in which there is a differential change during their occurrence, The index of "north high south low" and "east high west low" of precipitation can be used as the early circulation signal of low temperature rain and snow freezing events in southern China. You can predict a sustained event at least a week in advance. This paper also analyzes the characteristics of temperature and humidity in southern China in January 2016. The results show that, from 20 to 25 January 2016, the winter cold and wet events in southern China can be predicted. The "North High, South low" index turned positive 8 days earlier, and the "East High West low" index hovered around zero until it turned negative 4 days earlier and stabilized until the end of the event. It is shown once again that the defined circulation index can be used as a predictor of the persistent anomalous temperature and humidity events in the South. The causes of the arctic warming and the mechanism of its influence on the cold and dry are further analyzed. In the preceding period (late December 2015), the North American coastal sea surface temperature (SST) showed a warm anomaly, which stimulated the teleconnection wave train from the eastern coast of North America to northern Europe, resulting in the polar transport of the mean temperature gradient by the disturbance wind. The rapid warming of the Arctic caused polar vortex and polar cold air to move southward, which erupted after the accumulation in Central Siberia, causing a large-scale cooling in China. However, due to poor water vapor conditions in the same period, there was no sustained precipitation. Therefore, the southern region of our country for the persistence of abnormal cold and dry events.
【学位授予单位】：中国气象科学研究院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P468

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