Winter 2010‒2011: A Case Study of the Impact of La Niña on the Arctic Vortex

doi:10.13209/j.0479-8023.2016.100

Abstract

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

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

CLC Number:

P421

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.

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.

Figures/Tables 10

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

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

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)。)

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

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)

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

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

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

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

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