冬季两类ENSO事件对欧亚地区阻塞高压的影响

发布时间：2018-08-27 13:23

【摘要】：利用1979-2015年美国环境预报中心和美国大气研究中心发布的再分析资料和由日本海洋科学技术中心提供的El Ni?o/La Ni?a Modoki距平指数(EMI)资料,对比研究了近36 a冬季两类El Ni?o-南方涛动(ENSO)事件对欧亚关键区阻塞高压(阻高)的影响及其环流成因.结果表明,当发生El Ni?o(EN)事件时,欧亚3个关键区瞬时阻塞都有不同程度的减小,尤其是乌拉尔山地区瞬时阻塞减少32%,阻塞事件的平均持续天数降低了14.7%;La Ni?a(LN)事件导致乌拉尔山地区瞬时阻塞偏多53%,阻塞事件的平均持续天数增多27.9%,但导致了鄂霍次克海地区阻塞事件的平均持续天数减少24%;新型海温异常模态ENSO Modoki对于欧亚阻高的影响与传统的ENSO事件不同.发生EN Modoki时,与正常年份相比,欧亚3个关键区瞬时阻塞都有不同程度的增加,其中鄂霍次克海地区的瞬时阻塞偏多最多,达到55%,阻塞事件的平均持续天数增多18.2%;发生LN Modoki事件时,乌拉尔山地区瞬时阻塞偏多15%,阻塞事件平均持续天数偏多25%,但鄂霍次克海地区瞬时阻塞偏少29%,阻塞事件的平均持续天数偏少10.6%,两类ENSO事件对于贝加尔湖地区的阻高影响均较小.两类ENSO事件对阻高影响不同的直接原因是其对大气环流影响的不同.从500 hPa位势高度场及风场的配置可见,当发生EN事件时,乌拉尔山及鄂霍次克海地区风场有气旋性环流异常,配合位势高度场负异常,导致阻高偏少;发生LN事件时,乌拉尔山及贝加尔湖西部偏北的地区有大范围反气旋性环流异常,500 hPa位势高度偏强,阻高偏多;而在EN Modoki事件发生时,欧亚3个关键区的500 hPa位势高度均有不同程度的正异常,有利于3个地区阻高的偏多;在LN Modoki事件下,乌拉尔山及贝加尔湖北侧地区位势高度偏高,有利于这两个地区阻高的偏多,而不利于鄂霍次克海地区阻高的生成.
[Abstract]:Based on the reanalysis data released by the US Environmental Forecasting Center and the US Center for Atmospheric Research from 1979 to 2015 and the El Ni?O/La Ni?A Modoki anomaly index (EMI) data provided by the Japan Marine Science and Technology Center, the effects of two types of El Ni?O-Southern Oscillation (ENSO) events on the blocking high (blocking high) in the key Eurasian regions in the winter of recent 36 years were studied. The results show that the instantaneous blockage in the three key regions of Eurasia decreases in varying degrees when the El Ni?O (EN) event occurs, especially in the Ural Mountains, where the instantaneous blockage decreases by 32%, and the average duration of the blockage decreases by 14.7%; the La Ni?A (LN) event causes the instantaneous blockage in the Ural Mountains by 53% and the blockage events are flat. The average duration increased by 27.9%, but the average duration of blocking events in the Okhotsk Sea area decreased by 24%. The influence of ENSO Modoki on Eurasian blocking is different from that of traditional ENSO events. In the central Okhotsk Sea area, the instantaneous blockade is the most, reaching 55%, and the average duration of blocking events increases by 18.2%; in the case of LN Modoki, the instantaneous blockade is 15%, the average duration of blocking events is 25%, but in the Okhotsk Sea area, the instantaneous blockade is 29%, and the average duration of blocking events is 10.2%. The direct reason for the difference is that the two types of ENSO events have different effects on the atmospheric circulation. It can be seen from the configuration of 500 hPa potential height field and wind field that there is cyclonic circulation anomaly in the wind field of Ural Mountains and Okhotsk Sea when the EN event occurs. Negative anomalies in the height field of the conjunctive potential lead to less resistive height; large-scale anticyclonic circulation anomalies occur in the Ural Mountains and areas north-west of Lake Baikal when LN events occur, and 500 hPa geopotential height is relatively strong and resistive height is relatively high; and 500 hPa geopotential height in the three key regions of Eurasia has different degrees of positive anomalies when EN Modoki events occur. Under the LN Modoki event, the geopotential heights in the Ural Mountains and the Hubei side of Baikal are higher, which is beneficial to the high resistance in these two areas, but not conducive to the formation of the high resistance in the Okhotsk Sea area.
【作者单位】：兰州大学大气科学学院半干旱气候变化教育部重点实验室;
【基金】：国家自然科学基金项目(41305105) 中央高校基本科研业务费专项资金项目(LZUJBKY-2016-16)
【分类号】：P424;P732

【相似文献】