Interdecadal Variabilities of SCS Summer Monsoon Intensity

Li Xia; Liang Jianyin; Zheng Bin

Vol.18, NO.3, 2007

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Article Navigation > Journal of Applied Meteorological Science > 2007 > 18(3): 330-339

Li Xia, Liang Jianyin, Zheng Bin. Interdecadal variabilities of SCS summer monsoon intensity. J Appl Meteor Sci, 2007, 18(3): 330-339.

Citation:

Li Xia, Liang Jianyin, Zheng Bin. Interdecadal variabilities of SCS summer monsoon intensity. J Appl Meteor Sci, 2007, 18(3): 330-339.

Li Xia, Liang Jianyin, Zheng Bin. Interdecadal variabilities of SCS summer monsoon intensity. J Appl Meteor Sci, 2007, 18(3): 330-339.

Citation:

Li Xia, Liang Jianyin, Zheng Bin. Interdecadal variabilities of SCS summer monsoon intensity. J Appl Meteor Sci, 2007, 18(3): 330-339.

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Interdecadal Variabilities of SCS Summer Monsoon Intensity

1.
Chinese Academy of Meteorological Sciences, Beijing 100081
2.
Institute of Tropical and Marine Meteorology, CMA, Guangzhou 510080
3.
Guangzhou Central Meteorological Observatory, Guangzhou 510080

Received Date: 2005-12-14
Rev Recd Date: 2006-10-17
Publish Date: 2007-06-30

Abstract

Abstract

In order to diagnose the interdecadal variabilities of South China Sea (SCS) summer monsoon activities and reveal the inner relationships of the sea surface temperature and the general circulation anomalies to the interdecadal variabilities of SCS summer monsoon activity, by using NCEP/NCAR reanalysis grid data, the interdecadal phases of SCS summer monsoon are divided, the differences of the average fields in the different interdecadal phases and their causes are studied with composite and comparison analysis. The results show that the intensity of SCS summer monsoon is characterized by intedecadal variability that has an abrupt jump occurring around 1976. It can be divided into two phases. The first phase is from 1960 to 1976 and the second phase is from 1980 to 1998. Comparing the southwesterly over SCS in the second phase with that in the first phase, it is found that the average intensity is weaker, the amplitude of annual variation is greater, the periods are shorter and the ascending flow over the south and center of SCS is stronger in the second phase than that in the first phase. The temperatures in whole troposphere in summer drop over the China continent and rise over the surrounding ocean, leading in the increase of geopotential height in lower and middle levels in troposphere over China continent, and it is more than that over the ocean by the thermodynamic forcing process. The weakening of the pressure gradient between the continent and ocean can result in the enhancement of an anticyclonic anomalous circulation over the continent, leading to the weakening of the southwesterly over the north and center SCS. The temperatures in the troposphere in summer drop over the China continent and rise over the surrounding ocean, leading in geopotential height in lower and middle levels of troposphere over China continent increasing more than that over ocean through the thermodynamic forcing process. The weakening of pressure gradient between the continent and ocean can trigger an anticyclonic anomalous circulation over the continent, leading to the weakening of the southwesterly over the north and center SCS. As shown in the distribution of divergence wind field and vertical motion, it implies that the remarkable increase of sea surface temperature over the eastern equatorial Pacific Ocean may play an important role in enhancing the ascending motion over southern and center of SCS.
- South China Sea summer monsoon (SCSSM);
- interdecadal variation;
- change;
- intensity index

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References(19)

Figures and Tables

图 1 1960—2000年南海夏季风强度指数序列变化图 (a) 和南海夏季风指数的Mann-Kendall法突变检验图 (b)

(其中直线为平均值, 点线为均方差, 曲线为11年滑动平均)

Fig. 1 Variations of South China Sea summer monsoon (SCSSM) indices for the period of 1960—2000 (a) and detecting abrupt climatic change of SCSSM by using Mann-Kendall technique (b)

(horizontal lines denote mean values, the dot lines standard denote deviations and the curve line denotes 11-year running mean)

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图 2 南海夏季风强度指数序列的小波变换图 (a) 和小波变换方差的比较 (b)

(虚线为95%信度曲线)

Fig. 2 The wavelet transform of the South China Sea summer monsoon indices (a) and comparison of the wavelet powers for 1960—1976 and 1980—1998 periods (b)

(dash line is for 95% confidence level)

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图 3 850 hPa (a) 和500 hPa (b) 等压面平均风场差值 (矢量, 单位:m/s) 及其显著性检验

(阴影区和等值线分别为纬向风和经向风平均值差异通过95%信度区域)

Fig. 3 850 hPa (a) and 500 hPa (b) of average wind differenes and their significant test

(vectors are for wind differences, unit: m/s; shaded areas and isolines denote the differences of mean zonal winds and meridional winds exceed 95% level, respectively)

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图 4 850 hPa (a) 和200 hPa (b) 势函数差值 (等值线, 单位:10^-6 m/s; 阴影区为通过95%信度检验区域) 和辐散风差值 (矢量, 单位:m/s) 分布

Fig. 4 850 hPa (a) and 200 hPa (b) velocity potential differences (isolines, unit: 10^-6 m/s; shaded areas denote exceeding 95% level) and divergent wind differences (vectors, unit: m/s)

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图 5 850 hPa (a) 和500 hPa (b) 流函数差值 (等值线, 单位:m²/s; 阴影区为通过95%信度检验区域) 和旋转风差值 (矢量, 单位:m/s) 分布

Fig. 5 850 hPa (a) and 200 hPa (b) stream function differences (isolines, unit: m²/s; shaded areas denote exceeding 95% level) and rotation wind differences (vectors, units: m/s)

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图 6 850 hPa上平均位势高度 (单位:gpm)(a) 和平均温度 (单位:℃)(b) 差值场

(阴影区表示通过95%信度检验区域)

Fig. 6 Potential height differences (unit:gpm)(a) and air temperature differences (unit: ℃)(b) at 850 hPa

(shaded areas denote exceeding 95% level)

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图 7 气温差值垂直剖面图 (单位:℃, 阴影区为气温平均值的差异通过95%信度检验)

(a) 纬向平均 (105°~120°E), (b) 经向平均 (20°~40°N)

Fig. 7 Vertical section of air temperature differences (unit: ℃; areas exceeding 95% level are shaded)

(a) zonal mean (105°—120°E), (b) meridional mean (20°—40°N)

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图 8 纬向平均 (105°~120°E)(a) 和经向平均 (15°S~15°N)(b) 垂直速度剖面差值图 (单位:Pa/s) 以及经向平均 (15°S~15°N) 夏季海温差值随经度的变化曲线 (单位:℃)(c)

(阴影区为垂直速度平均值的差异通过95%信度检验区域)

Fig. 8 (a) Section of zonal mean vertical velocity in 105°—120°E (unit: Pa/s), (b) section of meridional mean vertical velocity in 15°S—15°N (unit: Pa/s), (c) differences of meridional mean (15°S—15°N) summer sea surface temperature (unit:℃)

(shaded areas denote vertical velocity exceeding 95% level)

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References

[1]	Tao Shiyan, Chen Longxun. The East Asian Summer Monsoon. Tokyo:Proceedings of International Conference on Monsoon in the Far East, 1985:5-8.
[2]	郭其蕴.东亚夏季风的变化与中国降水.热带气象学报, 1985, 1(1):44-52. http://www.cnki.com.cn/Article/CJFDTotal-RDQX198501005.htm
[3]	丁一汇, 薛纪善, 王守荣, 等. 1998年亚洲季风活动与中国的暴雨/洪涝∥丁一汇, 李崇银. 南海季风爆发和演变及其与海洋的相互作用. 北京: 气象出版社, 1999: 1-4.
[4]	何敏, 宋文玲. 南海夏季风对中国夏季降水的影响及预测∥丁一汇, 李崇银. 南海季风爆发和演变及其与海洋的相互作用. 北京: 气象出版社, 1999: 112-116.
[5]	吴尚森, 梁建茵, 李春晖.南海夏季风强度与我国汛期降水的关系.热带气象学报, 2003, 19(增刊):25-36. http://www.cnki.com.cn/Article/CJFDTOTAL-RDQX2003S1002.htm
[6]	李崇银, 李桂龙, 龙振夏.中国气候年代际变化的大气环流形势对比分析.应用气象学报, 1999, 10(增刊):1-8. http://www.cnki.com.cn/Article/CJFDTOTAL-YYQX9S1.000.htm
[7]	王绍武, 朱锦红.几个方兴未艾的气候学问题.应用气象学报, 1999, 10(增刊):104-113. http://www.cnki.com.cn/Article/CJFDTOTAL-YYQX9S1.012.htm
[8]	Li Chongyin, He Jinhai, Zhu Jinhong. A review of decadal/interdecadal climate variation studies in China. Adv Atmos Sci, 2004, 21(3):425-436. doi: 10.1007/BF02915569
[9]	李峰, 何金海.北太平洋海温与东亚夏季风相互作用的年代际变化.热带气象学报, 2000, 16(3):260-271. http://www.cnki.com.cn/Article/CJFDTOTAL-RDQX200003008.htm
[10]	黄刚.东亚夏季风环流指数与夏季气候变化关系的研究.应用气象学报, 1999, 10(增刊):61-69. http://www.cnki.com.cn/Article/CJFDTOTAL-YYQX9S1.007.htm
[11]	Wang Huijun. The weak of the Asian summer monsoon circulation after the end of 1970s. Adv Atmos Sci, 2001, 18:376-386. doi: 10.1007/BF02919316
[12]	Wang Huijun. Instability of the East Asian summer monsoon-ENSO relation. Adv Atmos Sci, 2002, 19:1-11. doi: 10.1007/s00376-002-0029-5
[13]	Huang Ronghui. Decadal variability of the summer monsoon rainfall in East Asian and its association with the SST anomalies in the tropical pacific. CLIVAR Exchange, 2001, 2:7-8.
[14]	Liang Jianyin, Wu Shangsen. Diagnostic analysis of interdecadal changes of the summer monsoon in the South China Sea. Acta Meteorologica Sinica, 2003, 17(1):81-95. https://www.researchgate.net/publication/294374680_Diagnostic_analysis_of_interdecadal_changes_of_the_summer_monsoon_in_the_South_China_Sea
[15]	王安宇, 冯瑞权, 吴池胜, 等.南海夏季风建立的气候特征Ⅱ———年代际变化.热带气象学报, 2002, 18(1):1-9. http://www.cnki.com.cn/Article/CJFDTOTAL-RDQX200201000.htm
[16]	Lin Ailan, Liang Jianyin, Gu Dejun, et al. On the relationship between convection intensity of Shouth China Sea summer monsoon and air-sea temperature difference in the tropical oceans. Acta Oceanologica Sinica, 2004, 23(2):267-278. https://www.researchgate.net/publication/282385314_On_the_relationship_between_convection_intensity_of_South_China_Sea_summer_monsoon_and_air-sea_temperature_difference_in_the_tropical_oceans
[17]	吴尚森, 梁建茵.南海夏季风强度指数及其变化特征.热带气象学报, 2001, 17(4):337-344. http://www.cnki.com.cn/Article/CJFDTOTAL-RDQX200104000.htm
[18]	Torrence Christopher, Compo G P. A practical guid to Wavelet Analysis. Bull Amer Meteor Soc, 1998, 79(1):61-78. doi: 10.1175/1520-0477(1998)079<0061:APGTWA>2.0.CO;2
[19]	魏凤英.现代气候统计诊断与预测技术.北京:气象出版社, 1999: