2010—2011年冬季La Niña事件对北半球极涡的影响分析

doi:10.13209/j.0479-8023.2016.100

摘要/Abstract

摘要：

为了探讨强极涡与La Niña事件之间的关系, 利用NCEP/NCAR (日平均、月平均位势高度及温度场)再分析资料对2010—2011年冬季进行个例研究。与气候态相比, 2010—2011年冬季北半球平流层极涡偏强, 同时, 显著的强海温负异常(La Niña事件)也持续整个冬季。结果表明, 受La Niña事件影响, 对流层环流场和温度场得到较大的调整, 出现PNA (Pacific North American)型异常环流形势和相对应的温度异常分布。2010年12月, 阿留申地区出现负值的热量经向输送, 使得该地区从对流层上升至平流层的行星波动与气候态相比明显减弱, 从而导致平流层极涡较气候平均态偏强。这一La Niña事件对平流层极涡影响的动力过程也从1948—2010年期间选出的13个冬季强La Niña事件的合成分析结果中得到证实。

关键词: 极涡, 行星波, La Niñ, a事件, 合成分析

Abstract:

The relationship between strong arctic vortex and the La Niña events is found out by a case study of winter 2010-2011, using the NCEP/NCAR (daily and month mean) dataset. During the winter 2010-2011, the Arctic vortex was extremely stronger and persistent longer than normal, at the same time La Niña signals were surprisingly strong and long-lasting. The impact of La Niña on the polar vortex was investigated. Results show that the Pacific/North American (PNA) Pattern and corresponding temperature anomalies were forced by this La Niña event and the atmospheric circulation was greatly modified, too. Due to the negative heat flux in Aleutian region, the wave activities from the troposphere to the stratosphere were much weaker than their climatology. In addition, composite analyses also verified this La Niña’s impact on Arctic Vortex, where 13 strongest La Niña cases during the period of 1948?2010 were selected.

Key words: arctic vortex, planetary waves, La Niñ, a events, composite analysis

中图分类号:

P421

石柳, 付遵涛. 2010—2011年冬季La Niña事件对北半球极涡的影响分析[J]. 北京大学学报自然科学版, 2017, 53(2): 321-328.

Liu SHI, Zuntao FU. Winter 2010‒2011: A Case Study of the Impact of La Niña on the Arctic Vortex[J]. Acta Scientiarum Naturalium Universitatis Pekinensis, 2017, 53(2): 321-328.

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链接本文: https://xbna.pku.edu.cn/CN/10.13209/j.0479-8023.2016.100

https://xbna.pku.edu.cn/CN/Y2017/V53/I2/321

图/表 10

图1 2010年10月至2011年4月NAM指数高度?时间图

Fig. 1 Height-time diagram of NAM from Oct., 2010 to Apr., 2011

Fig. 2 Geopotential height fields, zonal wave number 1 in red and 2 in blue

图3 12月三维EP通量气候态矢量图

Fig. 3 Three-dimensional EP-fluxes in Dec. for climatology

图4 (a) 2010年1月至2011年4月, Nino3.4 区海温月平均距平值; (b) 2010年11月至2011年2月冬季逐日PNA指数①(① 来自 CPC/NCEP 网站(http://www.cpc.noaa.gov/data/indices)。)

Fig. 4 (a) Time series of monthly SST anomalies of Nino3.4 region from Jan., 2010 to Apr., 2011; (b) time series of daily PNA index from Nov., 2010 to Feb., 2011①(① 来自 CPC/NCEP 网站(http://www.cpc.noaa.gov/data/indices)。)

图5 (a) 2010年12月500 hPa三维EP通量距平矢量图, 直线箭头表示水平的波动通量, 颜色填充表示垂直的波动通量(正值表示向上); (b) 12月500 hPa温度场?高度场气候态, 等值线为位势高度场(gpm); (c) 同(b), 2010年12月

Fig. 5 (a) 500 hPa three-dimensional EP-fluxes anomalies in Dec., 2010 (horizontal momentum component is marked as vectors and the vertical heat component is shaded in colors); (b) Spatial pattern of height and temperature for climatology in Dec.; (c) The same as (b), but in Dec., 2010

图6 (a) La Niña年12月500 hPa温度场?高度场合成图; (b) La Niña年12月500 hPa温度场?高度场去纬向平均距平合成图

Fig. 6 (a) Spatial pattern of height and temperature for the composite of La Niña years in Dec.; (b) Spatial pattern of height and temperature anomalies for the composite of La Niña years in Dec. (zonal mean was removed)

表1 1948—2011年期间的13个La Niña事件

Table 1 13 La Niña events selected during 1948?2011

序号	事件发生年份	序号	事件发生年份
1	1950—1951	8	1988—1989
2	1955—1956	9	1995—1996
3	1964—1965	10	1998—1999
4	1970—1971	11	1999—2000
5	1971—1972	12	2000—2001
6	1973—1974	13	2007—2008
7	1975—1976

图7 纬向波数1波(红色线)和2波(蓝色线)位势高度图

Fig. 7 Geopotential height fields, zonal wave number 1 in red and 2 in blue

图8 La Niña事件影响极涡的概念图

Fig. 8 Schematic diagram for La Niña event’s effect on Arctic vortex

图9 1948—2010年冬季11, 12月平均Nino3.4区海温距平值与1月NAM指数的散布图

Fig. 9 SST anomalies of Nino3.4 region (Nov. and Dec. mean) and NAM index (Jan.) during 1948?2010

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