VARIATION OF SUMMER MERIDIONAL WATER VAPOR TRANSPORT OVER EAST ASIA AND ITS IMPACT ON EXTREME PRECIPITATION
-
摘要: 东亚夏季降水的异常与水汽输送的变异密切相关。基于1958—2016年资料,研究了夏季东亚季风区经向水汽输送的主要变异特征及其对东亚夏季极端降水的影响。经向水汽输送的第一主变异模态表现出中国东部和西北太平洋上的水汽经向输送呈现反向异常,以年际变化为主。当中国东部向北输送的水汽增强(减弱)而西北太平洋向北输送减弱(增强),则中国东部大范围的极端降水量及频次增加(减少)。该模态与西太(西太平洋)副高西伸(东撤)有关,并主要受到热带中东印度洋海温的影响。第二变异模态以年代际变化为主兼有年际变化,表现在1980年后中国东部及邻近海域上空的经向水汽输送减弱,使得环渤海地区和华南沿海的极端降水量及频次减少而长江上、下游和贵州的极端降水量及频次增加。该模态与西太副高的减弱有关,并受到热带西太海温年代际增温的影响。第三变异模态以年际变化为主兼有年代际变化,反映中国长江以北地区和日本南部及附近区域的经向水汽输送的反相变化结构。长江以北水汽输送减弱(增强),可导致华北、东北的极端降水量及频次减少(增加)和长江下游及江南地区的极端降水量及频次的减少(增加)。该模态主要受欧亚大陆上空中高纬度纬向遥相关波列和热带印太(印度洋太平洋)海温异常的影响。Abstract: The abnormality of summer precipitation over East Asia is closely associated with anomalous water vapor transport. Based on the datasets from 1958 to 2016, this study investigates the variation features of meridional water vapor transport (MWVT) over East Asian monsoon region and its influence on the extreme precipitation over east China. Three leading anomalous patterns are identified by using the empirical orthogonal function (EOF) method. The first leading EOF mode reveals the inverse variation of MWVT over east China and over the western North Pacific, and the variation is mainly interannual time-scale. When MWVT is enhanced or weakened over east China and weakened or enhanced over the western Northern Pacific, the extreme precipitation rate, and the frequency over a large portion of east China increases or lessens. This mode is associated with the zonal shift of the western North Pacific subtropical high, which is attributed to the sea surface temperature over the tropical central-eastern Indian Ocean. The second EOF mode displays a significant interdecadal change around 1979/1980, and shows that MWVT is suppressed over east China and its adjacent marine area after 1980, leading to a decrease of extreme precipitation and its frequency over south China and around the Bohai Sea, but an increase over the upper and lower reaches of the Yangtze River and Guizhou Province. It is closely related to the intensity weakening of the western North Pacific subtropical high, associated with an interdecadal warming over the tropical western North Pacific. The third anomalous mode presents dominant interannual and minor interdecadal changes and shows an inverse change of MWVT over regions north of the Yangtze River and south Japan. The weakened MWVT over north China may give rise to less extreme precipitation and its frequency over north China and northeast China, and more over the lower reaches and the south of the Yangtze River. This mode is attributed to the impacts of a zonal Eurasian teleconnection over the mid-high latitudes and the sea surface temperature over the tropical Indo-Pacific Oceans.
-
图 2 标准化PC1回归的各物理量场的回归系数分布图
a.积分的水汽输送通量场(箭头)及其散度(填色,单位:10-5 kg/ (m2·s));b.沿110~120 °E平均的垂直剖面上的经向水汽通量(填色,单位:10-3 kg/(m·s))和经圈环流(箭头);c. 850 hPa风场(箭头)和500 hPa垂直速度(填色,单位:10-2 Pa/s);黑线、红线和蓝线分别为气候平均、PC1大于+1及小于-1的年分合成的1 500 gpm位势高度线;d. 200 hPa风场(箭头)及散度(填色,单位:10-6s-1);e.夏季极端降水日数(频次);f.夏季日极端降水量(填色,单位:mm)。黑色箭头及黑点表示回归系数通过0.05显著性水平检验。
图 3 标准化PC1回归的各物理量场的回归系数分布图
a. 850 hPa辐散风(箭头)、速度势函数(等值线,5×104 m2/s)和500 hPa垂直速度(填色,单位:10-2 Pa/s);b. 200 hPa辐散风(箭头)、速度势函数(等值线,间隔为:1×105 m2/s)和散度(填色,单位:10-6 s-1);c.沿b中所标的A (70 °E,10 °S)-B (100 °E,0 °)-C (128 °E,23 °N)-D (115 °E,38 °N)垂直剖面的垂直速度(填色,单位:0. 02 Pa/s)和垂直环流(箭头);d.海温场(填色,单位:K)。打点区通过0.05显著性水平检验。
图 6 同图 4,但为PC3的回归场
图 7 a.标准化PC3回归的250 hPa位势高度(填色,单位:gpm)、流函数(等值线,间隔:4×105 m2/s)和波活动通量(箭头);b.标准化印度降水(AIR)×(-1)回归的250 hPa位势高度场(等值线,单位:gpm);c.标准化PC3回归的海温场(填色,单位:℃);d.北大西洋海温(NAT)回归的250 hPa位势高度场(等值线,单位:gpm);e.热带海温(TSST)时间序列(黑线)和9年高斯低通滤波(红线);f.热带海温区(TSST)回归的500 hPa坐标垂直速度(填色,单位:10-2Pa/s)和850 hPa风场(箭头)。
a、b、d中的填色区,a、f中的黑色箭头,以及c、f中的打点区,表示通过0.05显著性水平检验。
表 1 PC3与中纬度波列(RWI)、全印度降水(AIR)、北大西洋海温三极子(NAT)、赤道中东太平洋海温(Niño3.4)、热带印度洋(TIO)的相关系数
“*”表示通过0.05显著性水平检验。 参数 RWI AIR NAT Niño3.4 TIO PC3 0.73* 0.38* 0.52* 0.42* 0.34* -
[1] 黄荣辉, 张振洲, 黄刚, 等.夏季东亚季风区水汽输送特征及其与南亚季风区水汽输送的差别[J].大气科学, 1998, 22(4):76-85. [2] 陈际龙, 黄荣辉.亚澳季风各子系统气候学特征的异同研究Ⅱ.夏季风水汽输送[J].大气科学, 2007, 31(5):766-778. [3] 黄荣辉, 陈际龙.我国东、西部夏季水汽输送特征及其差异[J].大气科学, 2010, 34(6):1 035-1 045. [4] 田红, 郭品文, 陆维松.中国夏季降水的水汽通道特征及其影响因子分析[J].热带气象学报, 2004, 20(4):401-408. [5] SUN L, SHEN B Z, SUI B. A study on water vapor transport and budget of heavy rain in Northeast China[J]. Adv Atmos Sci, 2010, 27(6): 1 399-1 414. [6] ZHOU T, YU R. Atmospheric water vapor transport associated with typical anomalous summer rainfall patterns in China[J]. J Geophys Res Atmos, 2005, 110(D8): 211. [7] 方浩, 乔云亭.中国东部夏季极端降水时空分布及环流背景[J].热带气象学报, 2019, 35(4):517-527. [8] ZHANG R H. Relations of water vapor transport from Indian Monsoon with that over East Asia and the summer rainfall in China[J]. Adv Atmos Sci, 2001, 18(5): 1 005-1 017. [9] JIANG T, KUNDZEWICZ Z W, SU B. Changes in monthly precipitation and flood hazard in the Yangtze River Basin, China[J]. Int J Climatol, 2008, 28(11): 1 471- 1 481. [10] SUN B, ZHU Y, WANG H. The recent interdecadal and interannual variation of water vapor transport over eastern China[J]. Adv Atmos Sci, 2011, 28(5):1 039-1 048. [11] CHEN B, XU X D, ZHAO T L. Main moisture sources affecting lower Yangtze River Basin in boreal summers during 2004-2009[J]. Int J Climatol, 2013, 33(4): 1 035-1 046. [12] LI X, LU R. Extratropical factors affecting the variability in summer precipitation over the Yangtze River Basin, China[J]. J Climate, 2017, 30(20): 8 357-8 374. [13] UPPALA S M, KALLBERG P W, SIMMONS A J, et al. The ERA-40 re-analysis[J]. Quart J Roy Meteorol Soc, 2005, 131(612): 2 961- 3 012. [14] DEE D, UPPALA S M, Simmons A J, et al. The ERA-Interim reanalysis: configuration and performance of the data assimilation system[J]. Quart J Roy Meteorol Soc, 2011, 137(656): 553-597. [15] HARRIS I, JONES P D, OSBORN T J, et al. Updated high-resolution grids of monthly climatic observations - the CRU TS3.10 Dataset[J]. Int J Climatol, 2014, 34(3): 623-642. [16] WANG B, CLEMENS S C, LIU P. Contrasting the Indian and East Asian monsoons: Implications on geologic timescales[J]. Marine Geology, 2003, 201(1-3): 5-21. [17] ENOMOTO T, HOSKINS B J, MATSUDA Y. The formation mechanism of the Bonin high in August[J]. Quart J Roy Meteorol Soc, 2003, 129(587):157-178. [18] ENOMOTO T. Interannual variability of the Bonin high associated with the propagation of Rossby waves along the Asian jet[J]. J Meteorol Soc Jpn, 2004, 82(4): 1 019-1 034. [19] TAKAYA K, NAKAMURA H. A formulation of a phase-independent wave-activity flux for stationary and migratory quasigeostrophic eddies on a zonally varying basic flow[J]. J Atmos Sci, 2001, 58(6): 608-627. [20] RODWELL M J, HOSKINS B J. Monsoons and the dynamics of deserts[J]. Quart J Roy Meteorol Soc, 1996, 122(534): 1 385-1 404. [21] WANG B, WU R G, LAU K M. Interannual variability of the Asian summer monsoon: Contrasts between the Indian and the western North Pacific-East Asian monsoons[J]. J Climate, 2001, 14(20): 4 073-4 090. [22] KRISHNAN R, SUGI M. Baiu rainfall variability and associated monsoon teleconnection[J]. J Meteor Soc Japan, 2001, 79(3): 851-860. [23] LU R Y, OH J H, KIM B J. A teleconnection pattern in upper-level meridional wind over the North African and Eurasian continent in summer[J]. Tellus A, 2002, 54(1): 44-55. [24] LIU R, HUANG R. Linkages between the South and East Asian monsoon water vapor transport during boreal summer[J]. J Climate, 2019, 32(14): 4 509- 4 524. [25] ZUO J Q, LI W J, SUN C H, et al. Impact of the North Atlantic sea surface temperature tripole on the East Asian summer monsoon[J]. Adv Atmos Sci, 2013, 30(4): 1 173-1 186. [26] GILL A E. Some simple solutions for heat-induced tropical circulation[J]. Q J Roy Meteorol Soc, 1980, 106(449): 447-462. [27] 吴国雄, 刘平, 刘屹岷, 等.印度洋海温异常对西太平洋副热带高压的影响——大气中的两级热力适应[J].气象学报, 2000, 58(5):513-522. [28] XIE S P, HU K M, Hafner J, et al. Indian Ocean capacitor effect on Indo-western Pacific climate during the summer following El Niño[J]. J Climate, 2009, 22(3): 730-747. [29] WU B, LI T, ZHOU T. Relative contributions of the Indian Ocean and local SST anomalies to the maintenance of the western North Pacific anomalous anticyclone during the El Niño decaying summer[J]. J Climate, 2010, 23(11): 2 974-2 986.