THE VARIATION CHARACTERISTICS OF 10~30 DAYS OSCILLATION INTENSITY OF SPRING OVER THE SOUTH CHINA SEA-WESTERN PACIFIC OCEAN AND THEIR EFFECTS ON THE SOUTH CHINA SEA SUMMER MONSOON ONSET
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摘要: 采用NCEP再分析资料,揭示了南海-西太平洋春季对流存在显著的10~30天振荡周期。在年际尺度上,南海-西太平洋春季对流10~30天振荡强度(简称SCSWP_SISO)与南海夏季风爆发日期存在显著的负相关关系。当春季菲律宾和西太平洋海温偏高、赤道太平洋中部及以东地区海温偏低时,索马里、110 °E越赤道气流会加强,南海-西太平洋偏西风加强,产生异常气旋性环流,垂直上升运动增强,水汽异常偏多,东西风切变增强,有利于SCSWP_SISO增强。而SCSWP_SISO增强时,有由南往北、自西向东的异常气旋传播,从而减弱低层副热带高压使之较早撤出南海,南海夏季风得以较早爆发。反之亦然。在不同的年代际背景下,SCSWP_SISO经历了偏弱、较弱和偏强的变化,但影响其变化的因子并不完全一致。在第一阶段(1958—1976年),主导因子是南海-西太平洋冷的海温与异常下沉运动、异常减弱的水汽-对流条件。在第二阶段(1977—1993年),主导因子为中东太平洋异常偏冷的海温以及局地异常减弱的风场垂直切变。在第三阶段(1994—2011年),主导因子为热带海温的整体偏暖、风场垂直切变的增强以及水汽-对流的加强。但随着SCSWP_SISO的年代际增强,其与南海夏季风爆发日期的相关关系却呈现下降趋势。Abstract: Based on the NCEP reanalysis data, the 10~30 days significant sub-seasonal variability period of spring (March-May) convection over the South China Sea-Western Pacific Ocean is revealed. On interannual scale, there exist a negative significant correlation between the intensity variation of the 10~30 days oscillation over the South China Sea-Western Pacific Ocean regions (SCSWP_SISO) and the South China Sea summer monsoon onset. When the sea surface temperature anomalies (SSTA) of the Philippines and the western Pacific Ocean is high, the central and east equatorial Pacific SSTA is low, the crossing equatorial currents of Somali and around 110~120 °E areas and westerly winds from the tropical Indian Ocean will strengthen. Meanwhile, an obvious anomalous cyclonic circulation over the South China Sea-Western Pacific Ocean occurs, along with enhancing vertical ascending motion, increasing water vapor anomalies and strengthening wind vertical shear, which results in enhancing SCSWP_SISO. Due to the SCSWP_SISO increase, propagation of an anomalous cyclone from south to north and west to east leads to early withdrawal of lower subtropical high from the South China Sea and the South China Sea summer monsoon breaks out earlier. And vice versa. Under the background of different decadal, SCSWP_SISO has experienced the change of the weak, the weaker and strong, while the influencing factors are not entirely consistent. In the first stage (1958—1976), the negative SSTA over the South China Sea-Western Pacific and abnormal subsidence, decreasing water vapor-convection play a leading role. In the second stage (1977—1993), the main factors are the abnormal cold SST in the Middle East Pacific and local anomalies reducing vertical shear of wind field. In the third stage (1994—1994), the overall warming SST in the tropical, abnormal increasing vertical shear of wind field and convection are the key factors. But, as the SCSWP_SISO increases, its relation with the date of the South China Sea summer monsoon onset is a declining trend.
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图 3 春季变量合成异常场分布(振荡强年减去弱年)
a.海温(深、浅阴影表示正、负海温,*表示通过0.05显著性水平检验,单位:℃);b. 850 hPa风场(矢量,粗箭头表示通过0.05显著性水平检验,单位:m/s)和700 hPa水汽(阴影,#号表示通过0.05显著性水平检验,单位:g/kg);c. 1 000~100 hPa共12层的经向风场V和气压垂直速度W构成的Hadley环流(经度平均取105~130 °E)(深浅阴影为通过0.05显著性水平检验,V单位:m/s,W单位:Pa/s,放大100倍);d. 1 000~100 hPa共12层的纬向风差值分布(经度平均取105~130 °E)(深、浅阴影表示通过0.05显著性水平检验,单位:m/s)。
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[1] HE J H, ZHU Z W. The relation of South China Sea monsoon onset with the subsequent rainfall over the subtropical East Asia[J]. Int J Climatol, 2015, 35(15):4 547-4 556, Doi:10.1002/joc.4305. [2] LAU K M, YANG G J, SHEN S H. Seasonal and intraseasonal climatology of summer monsoon rainfall over East Asia[J]. Mon Wea Rev, 2001, 116(1): 18-37. [3] ANNAMALAI H, SLINGO J. Active/break cycles: Diagnois of the intraseasonal variability of the Asian summer monsoon[J]. Clim Dyn, 2001, 18(1-2): 85-102. [4] LAU K M, CHAN P H. Intraseasonal and interannual variations of tropical convection: A possible link between the 40-50 day oscillation an ENSO?[J]. J Atmos Sci, 1988, 45(3): 506-521. [5] HSU H H, WENG C H. Northward propagation of intraseasonal oscillation in the western North Pacific during the boreal summer: Structure and mechanism[J]. J Clim, 2001, 14(18): 3 834-3 850. [6] KAJIKAWA Y, YASUNARI T. Interannual variability of the 10~25 and 30~60-day variation over the South China Sea during boreal summer[J]. Geophys Res Lett, 2005, 32(4):319-325, doi:10.1029/2004GL021836. [7] JU J, ZHAO E. Impacts of the low frequency oscillation in East Asian summer monsoon on the drought and flooding in the middle and lower valley of Yangtze River[J]. J Trop Meteor, 2005, 21(2): 163-171. [8] LAU K M, CHAN P H. Aspects of the 40-50 day oscillation during the northern summer as inferred from outgoing longwave radiation[J]. Mon Wea Rev, 1985, 113(11):1 354-1 367. [9] 穆明权, 李崇银. 1998年南海夏季风的爆发与大气季节内振荡的活动[J].气候与环境研究, 2000, 5(4):375-387. [10] 温之平, 黄荣辉, 贺海晏, 等.中高纬大气环流异常和低纬30~60天低频对流活动对南海夏季风爆发的影响[J].大气科学, 2006, 30(5):952-964. [11] 林爱兰.南海夏季风的低频特征[J].热带气象学报, 1998, 14 (2):113-118. [12] 陈尚锋, 温之平, 陈文.南海地区大气30~60天低频振荡及其对南海夏季风的可能影响[J].大气科学, 2011, 35 (5):982-992. [13] XIE S, HUANG P, HUANG R. Role of phase transition of intraseasonal oscillation on the South China Sea summer monsoon onset[J]. Clim Dyn, 2015, 45(1-2):125-137. doi:10. 1007/s00382-014-2264-8. [14] NITTA T, YAMADA S. Recent warming of tropical sea surface temperature and its relationship to Northern Hemisphere circulation[J]. J Meteor Soc Japan, 1989, 67(12):375-383. [15] KACHI M, NITTA T. Decadal variations of the global atmosphere-ocean system[J]. J Meteor Soc Japan, 1997, 75(3): 988-993. [16] 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[J].应用气象学报, 1999, 10(增刊): 1-8. [17] 郭其蕴, 蔡静宁, 邵学梅, 等.东亚夏季风的年代际变率对中国气候的影响[J].地理学报, 2003, 58(4): 569-576. [18] WANG H. The weakening of the Asian monsoon circulation after the end of 1970's[J]. Adv Atmos Sci, 2001, 18(3): 376-386. [19] HUANG R. Decadal variability of the summer monsoon rainfall in East Asia and its association with the SST anomalies in the tropical Pacific[J]. CLIVAR Exchanges, 2001, No.2, International CLIVAR Project Office, Southampton, United Kingdom, 7-8. [20] LIANG J, WU S. Diagnostic Analysis of Interdecadal Change of the Summer Monsoon in the South China Sea[J]. ACTA Meteorological Sinica, 2003, 17(suppl): 81-94. [21] 戴念军, 谢安, 张勇.南海夏季风活动的年际和年代际特征[J].气候与环境研究, 2000, 5(4): 363-374. [22] LIANG J, YANG S, LI C, et.al. Long-term changes in the South China Sea summer monsoon revealed by station observations of the Xisha Islands[J]. J Geophys Res, 112(D10):185-194, doi: 10.1029/2006JD007922. [23] LI C, LI T, LIANG J, et al. Interdecadal Variations of Meridional Winds in the South China Sea and Their Relationship with Summer Climate in China[J]. J Clim, 2010, 23(4): 825-841. [24] KWON M H, JHUN J G, WANG B, et al. Decadal change in relationship between east Asian and WNP summer monsoons[J]. Geophys Res Lett, 2005, 321(16):101-120, doi: 10.1029/2005gl023026. [25] KWON M H, JHUN J G, HA K J. Decadal change in east Asian summer monsoon circulation in the mid-1990s[J]. Geophys Res Lett, 2007, 34(21):377-390, doi:10.1029/2007GL031977. [26] YIM S Y, YEH S W, WU R, et al. The influence of ENSO on decadal variations in the relationship between the East Asian and western North Pacific summer monsoons[J]. J Climate, 2008, 21(13): 3 165-3 179. [27] WANG B, HUANG F, WU Z, et al. Multi-scale climate variability of the South China Sea monsoon: A review[J]. Dyn Atmos Oceans, 2009, 47(1): 15-37. [28] KAJIKAWA Y, WANG B. Interdecadal change of the South China Sea summer monsoon onset[J]. J Clime, 2012, 25(9):3 207-3 218. [29] KAJIKAWA Y, YASUNARI T, WANG B. Decadal change in intraseasonal variability over the South China Sea[J]. Geophys Res Lett, 2009, 36(6): 150-164, doi:10.1029/2009gl037174. [30] SMITH T M, REYNOLDS R W. Extended reconstruction of global sea surface temperatures based on COADS data (1854—1997)[J]. J Clim, 2003, 16(10):1 495-1 510. [31] SMITH T M, REYNOLDS R W. Improved Extended Reconstruction of SST (1854-1997) [J]. J Clim, 2004, 17(13): 2 466-2 477. [32] TRENBERTH K E. Signal versus noise in the Southern Oscillation[J]. Mon Wea Rev, 1984, 112(2): 326-332. [33] 梁建茵, 吴尚森.南海西南季风爆发日期及其影响因子[J].大气科学, 2002, 26(6): 829-844. [34] WANG B, XIE X. A model for the boreal summer intraseasonal oscillation[J]. J Atmos Sci, 1997, 54(1): 72-86. [35] 黄荣辉, 孙凤英.热带西太平洋暖池的热状况及其上空的对流活动对东亚夏季气候异常的影响[J].大气科学, 1994, 18(2): 141-151. [36] 梁建茵, 吴尚森.太平洋海温异常对南海西南季风建立早晚的影响——数值模拟研究[J].海洋学报, 2003, 25(1): 28-41. [37] JIANG X, LI T, WANG B. Structures and mechanisms of the northward propagating boreal summer intraseasonal oscillation[J]. J Clim, 2004, 17(5): 1 022-1 039. [38] LIU F, WANG B. A Mechanism for explaining the maximum intraseasonal oscillation center over the Western North Pacific[J]. J Clim. 2014, 27(2): 958-968. -