Changes of summer water vapor in Bengal region and its linkage with the interdecadal Pacific oscillation

doi:10.11755/j.issn.1006-7639(2023)-03-0380

Abstract

Abstract:

Located in the middle zone between the Tibetan Plateau and the Bay of Bengal, the Indian Peninsula and the Indo-China Peninsula, the Bengal region is the first region affected by the outbreak of the Asian monsoon. The change of water vapor in the Bengal region is of great significance to the climate of South Asia and East Asia. The causes and possible physical processes of the atmospheric precipitable water (APW) change in summer (June-September) in the Bengal region are analyzed using the ERA5 reanalysis data from the European Center for Medium-Range Weather Forecasts (ECMWF) and sea surface temperature data from the National Oceanic and Atmosphere Administration (NOAA) from 1979 to 2020. The results show that APW in the Bengal region is the largest at the same latitude in southern Asia. The summer APW accounts for more than 50% of the whole year, and the average summer APW presents a significant increase trend. According to the whole layer water vapor budgets and water vapor budget vertical profiles of the four boundaries of the Bengal region, the trends of the whole layer water vapor budgets of the eastern and southern boundaries are favorable to the increase of APW there, while the trends of the whole layer water vapor budgets of the western and northern boundaries are unfavorable to the increase of APW there. The summer APW in the Bengal region is negatively correlated with the interdecadal Pacific oscillation (IPO) on both inter-annual and inter-decadal scales. When the IPO is in its positive phase, in the lower troposphere, the westerly (easterly) wind anomaly prevails in the equatorial Pacific (equatorial Indian Ocean), while it is the opposite in the upper troposphere, indicating a weakening of the Walker circulation over the Indian and Pacific Oceans. The Gill-type anticyclonic circulation anomaly is observed in the lower troposphere in the north and south sides of the equatorial Indian Ocean. The Indian monsoon is weak, and a northwest wind anomaly prevails from the Arabian Peninsula to the Bengal region. The westerly airflow is not conducive to the transport of water vapor to the Bengal region, while the sinking airflow accompanying the anticyclonic circulation is not conducive to the convergence of water vapor in this region, resulting in the reduction of APW in the Bengal region. On the contrary, when the IPO is in a negative phase, it is favorable for the increase of APW in the Bengal region in summer.

Key words: the Bengal region, atmospheric precipitable water, water vapor transport, sea surface temperature, IPO

摘要：

孟加拉地区位于青藏高原与孟加拉湾、印度半岛与中南半岛的中间地带，是亚洲季风爆发率先影响的区域，孟加拉地区的水汽变化对亚洲南部以及东亚气候有重要的指示意义。采用1979—2020年欧洲中期天气预报中心ERA5再分析资料和美国国家海洋和大气管理局提供的海表面温度等资料，分析孟加拉地区夏季（6—9月）大气可降水量（Atmospheric Precipitable Water，APW）变化成因及其可能的物理过程。结果表明，孟加拉地区APW在亚洲南部同纬度最大，夏季APW占全年50%以上，且夏季平均APW呈显著增加趋势。从孟加拉地区4个边界整层的水汽收支和水汽收支垂直廓线来看，西边界与北边界的水汽收支趋势不利于该区域水汽增加，而东边界与南边界的水汽收支趋势利于该区域水汽增加。孟加拉地区夏季APW与太平洋年代际振荡（IPO）在年际和年代际尺度上均呈显著负相关。当IPO为正位相时，对流层低层赤道太平洋（赤道印度洋）盛行西风（东风）异常，对流层高层与之相反，表明印度洋与太平洋上的Walker环流减弱;对流层低层的赤道印度洋南北两侧呈Gill型反气旋环流异常，印度季风偏弱，阿拉伯半岛至孟加拉一带盛行西北风异常，西风气流不利于水汽向孟加拉地区输送，同时反气旋型环流伴随的下沉气流不利于该区域水汽汇聚，使得孟加拉地区APW减少。反之，当IPO为负位相时，则有利于孟加拉地区夏季APW增加。

关键词: 孟加拉地区, 大气可降水量, 水汽输送, 海表面温度, 太平洋年代际振荡

CLC Number:

P467

GUO Jingyan, XIAO Dong. Changes of summer water vapor in Bengal region and its linkage with the interdecadal Pacific oscillation[J]. Journal of Arid Meteorology, 2023, 41(3): 380-389.

郭静妍, 肖栋. 孟加拉地区夏季水汽变化及其与太平洋年代际振荡的联系[J]. 干旱气象, 2023, 41(3): 380-389.

Figures/Tables 10

Fig.1 Spatial distribution of seasonal mean atmospheric precipitable water in southern Asia during 1979-2020 （Unit： kg·m-2）（The red rectangle is the Bengal region. the same as below）（a） spring，（b） summer，（c） autumn，（d） winter

Fig.2 The monthly change of average atmospheric precipitable water in the Bengal region during 1979-2020 （a）， the time series and its trend of average atmospheric precipitable water from June to September in the Bengal region during 1979-2020 （b）

Fig.3 Spatial distribution of variation trends of the average vector wind （arrow vectors， Unit： m·s-1·a-1） and specific humidity （the shaded， Unit： 10-4 ?kg·kg-1·a-1） at 850 hPa （a） and the vertical integrated water vapor flux （arrow vectors， Unit： kg·m-1·s-1·a-1） and divergence （the shaded， Unit： 10-9 s-1·a-1）（b） in summer in southern Asia from 1979 to 2020（the dotted passing the significance test of α=0.1）

Fig.4 Time series and trends of water vapor budget of each boundary （a） and net water vapor budget （b） in the Bengal region in summer averaged from June to September during 1979-2020

Tab.1 The trends of water vapor budget in each boundary and net water vapor budget in the Bengal region and physical meanings of positive and negative climatic states

	气候平均	对区域水汽的贡献	趋势	对区域水汽的贡献
东边界	正值	区域内水汽减少	负值	支出水汽减少，区域内水汽增多
西边界	负值	区域内水汽减少	负值	支出水汽增加，区域内水汽减少
北边界	正值	区域内水汽减少	正值	支出水汽增加，区域内水汽减少
南边界	正值	区域内水汽增加	正值	收入水汽增加，区域内水汽增加
孟加拉区域	正值	区域内水汽增加	正值	收入水汽增加，区域内水汽增加

Fig.5 The vertical distribution of water vapor budget of each boundary and net water vapor budget （a） and their trends （b） in the Bengal region in summer averaged from June to September during 1979-2020 （the stars passing the significance test of α=0.1）

Fig.6 The distribution of correlation coefficients between APW in summer in the Bengal region and average sea surface temperature in the same period during 1979-2020 （the dotted area passing the significance test of α=0.05）

Fig.7 Time series of summer average atmospheric precipitable water and IPO index in the Bengal region from 1979 to 2020

Fig.8 The 850 hPa （a） and 200 hPa （b） geopotential height （the color shaded， Unit： gpm） and horizontal wind （arrow vectors， Unit： m·s-1） regressed by IPO index averaged in summer during 1979-2020 （The dotted area and green arrow vectors pass the significance test of α=0.05）

Fig.9 The 850 hPa water vapor flux （arrow vectors， Unit： kg·m-1·s-1） and atmospheric precipitable water （the color shaded， Unit： kg·m-2） regressed by IPO index averaged in summer during 1979-2020 （The dotted area and red vector arrows pass the significance test of α=0.10）（a） 50 °E-120 ° E， 20 ° S-50 ° N，（b） 75 ° E-105 ° E， 15 ° N-35 ° N

References 42

[1]	蔡学湛, 2001. 青藏高原雪盖与东亚季风异常对华南前汛期降水的影响[J]. 应用气象学报, 12(3): 358-367.
[2]	陈隆勋, 周秀骥, 李维亮, 等, 2004. 中国近80年来气候变化特征及其形成机制[J]. 气象学报, 62(5): 634-646.
[3]	丁一汇, 孙颖, 刘芸芸, 等, 2013. 亚洲夏季风的年际和年代际变化及其未来预测[J]. 大气科学, 27(2): 253-280.
[4]	郝立生, 丁一汇, 闵锦忠, 2016. 东亚夏季风变化与华北夏季降水异常的关系[J]. 高原气象, 35(5): 1 280-1 289.
[5]	李崇银, 2000. 气候动力学引论[M]. 北京: 气象出版社.
[6]	李栋梁, 张茜, 姚慧茹, 等, 2016. 北印度夏季风与中国河套及邻近地区盛夏降水的联系[J]. 高原气象, 35(6): 1 512-1 523.
[7]	李峰, 何金海, 2000. 北太平洋海温异常与东亚夏季风相互作用的年代际变化[J]. 热带气象学报, 16(3): 260-271.
[8]	唐民, 吕俊梅, 2007. 东亚夏季风降水年代际变异模态及其与太平洋年代际振荡的关系[J]. 气象, 33(10): 88-95.
[9]	陶诗言, 朱文妹, 赵卫, 1988. 论梅雨的年际变异[J]. 大气科学, 12(增刊1): 13-21.
[10]	王会军, 范可, 2013. 东亚季风近几十年来的主要变化特征[J]. 大气科学, 37(2): 313-318.
[11]	王绍武, 赵宗慈, 1979. 我国旱涝36年周期及其产生的机制[J]. 气象学报, 37(1): 64-73.
[12]	王绍武, 2001. 现代气候学研究进展[M]. 北京: 气象出版社.
[13]	王文, 许金萍, 蔡晓军, 等, 2017. 2013年夏季长江中下游地区高温干旱的大气环流特征及成因分析[J]. 高原气象, 36(6): 1 595-1 607.
[14]	徐建军, 朱乾根, 施能, 1996. 年代际气候变率问题的研究[J]. 南京气象学院学报, 19(4): 488-495.
[15]	尹树新, 江燕如, 1993. 季风异常与江淮地区旱涝关系[J]. 南京气象学院学报, 16(1): 89-96.
[16]	张人禾, 1999. El Ni(n)o盛期印度夏季风水汽输送在我国华北地区夏季降水异常中的作用[J]. 高原气象, 18(4): 567-574.
[17]	ARAYA-MELO P A, CRUCIFIX M, BOUNCEUR N, 2015. Global sensitivity analysis of the Indian monsoon during the Pleistocene[J]. Climate of the Past, 11(1): 45-61. DOI URL
[18]	BOSMANS J H C, ERB M P, DOLAN A M, et al, 2018. Response of the Asian summer monsoons to idealized precession and obliquity forcing in a set of GCMs[J]. Quaternary Science Reviews, 188: 121-135. DOI URL
[19]	CHEN B, XU X D, ZHAO T, 2013. Main moisture sources affecting lower Yangtze River Basin in boreal summers during 2004-2009[J]. International Journal of Climatology, 33(4): 1 035-1 046.
[20]	CHENG T F, LU M, 2020. Moisture source-receptor network of the East Asian summer monsoon land regions and the associated atmospheric steerings[J]. Journal of Climate, 33(21): 9 213-9 231. DOI URL
[21]	CLEMENS S, YAMAMOTO M, THIRUMALAI K, et al, 2021. Remote and local drivers of Pleistocene South Asian summer monsoon precipitation: a test for future predictions[J]. Science Advances, 7(23): 1-15.
[22]	DESER C, PHILLIPS A S, HURRELL J W, 2004. Pacific interdecadal climate variability: linkages between the tropics and the north Pacific during Boreal winter since 1900[J]. Journal of Climate, 17(16): 3 109-3 124. DOI URL
[23]	GILL A E, 1980. Some simple solutions for heat-induced tropical circulation[J]. Quarterly Journal of the Royal Meteorological Society, 106(449): 447-462. DOI URL
[24]	HALL A, MANABE S, 1999. The role of water vapor feedback in unperturbed climate variability and global warming[J]. Journal of climate, 12(8): 2 327-2 346.
[25]	HAN W, MEEHL G A, HU A, et al, 2014. Intensification of decadal and multi-decadal sea level variability in the western tropical Pacific during recent decades[J]. Climate Dynamics, 43(5/6):1 357-1 379.
[26]	HE C, LIN A, GU D, et al, 2017. Interannual variability of Eastern China summer rainfall: the origins of the meridional triple and dipole modes[J]. Climate Dynamics, 48(1): 683-696. DOI URL
[27]	HENLEY B J, GERGIS J, KAROLY D J, et al, 2015. A tripole index for the interdecadal Pacific oscillation[J]. Climate dynamics, 45(11/12): 3 077-3 090.
[28]	HERSBACH H, BELL B, BERRISFORD P, et al, 2020. The ERA5 global reanalysis[J]. Quarterly Journal of the Royal Meteorological Society, 146(730): 1 999-2 049.
[29]	HUANG B, THORNE P W, BANZON V F, et al, 2017. Extended reconstructed sea surface temperature, version 5 (ERSSTv5): upgrades, validations, and intercomparisons[J]. Journal of Climate, 30(20): 8 179-8 205.
[30]	HUANG X, ZHOU T, DAI A, et al, 2020. South Asian summer monsoon projections constrained by the interdecadal Pacific oscillation[J]. Science advances, 6(11): 1-10.
[31]	KRISHNAN R, SUGI M, 2003. Pacific decadal oscillation and variability of the Indian summer monsoon rainfall[J]. Climate Dynamics, 21(3): 233-242. DOI URL
[32]	LIU F, ZHANG W, JIN F F, et al, 2021. Decadal modulation of the ENSO-Indian ocean basin warming relationship during the decaying summer by the interdecadal Pacific oscillation[J]. Journal of Climate, 34(7): 2 685-2 699.
[33]	MANTUA N J, HARE S R, ZHANG Y, et al, 1997. A Pacific interdecadal climate oscillation with impacts on salmon production[J]. Bulletin of the American Meteorological Society, 78(6): 1 069-1 080.
[34]	NEWMAN M, ALEXANDER M A, AULT T R, et al, 2016. The Pacific decadal oscillation, revisited[J]. Journal of Climate, 29(12): 4 399-4 427.
[35]	NEWMAN M, COMPO G P, ALEXANDER M A, 2003. ENSO-forced variability of the Pacific decadal oscillation[J]. Journal of Climate, 16(23): 3 853-3 857.
[36]	POWER S, CASEY T, FOLLAND C, et al, 1999. Inter-decadal modulation of the impact of ENSO on Australia[J]. Climate dynamics, 15(5): 319-324. DOI URL
[37]	SHI Y, JIANG Z, LIU Z, et al, 2020. A Lagrangian analysis of water vapor sources and pathways for precipitation in East China in different stages of the East Asian summer monsoon[J]. Journal of Climate, 33(3): 977-992. DOI URL
[38]	SOLOMON S, ROSENLOF K H, PORTMANN R W, et al, 2010. Contributions of stratospheric water vapor to decadal changes in the rate of global warming[J]. Science, 327(5970): 1 219-1 223.
[39]	TRENBERTH K E, HURRELL J W, 1994. Decadal atmosphere-ocean variations in the Pacific[J]. Climate Dynamics, 9(6): 303-319. DOI URL
[40]	TRENBERTH K E, 1990. Recent observed interdecadal climate changes in the Northern Hemisphere[J]. Bulletin of the American Meteorological Society, 71(7): 988-993. DOI URL
[41]	WU X, MAO J, 2019. Decadal changes in interannual dependence of the Bay of Bengal summer monsoon onset on ENSO modulated by the Pacific Decadal Oscillation[J]. Advances in Atmospheric Sciences, 36(12): 1 404-1 416.
[42]	YANG Q, MA Z, FAN X, et al, 2017. Decadal modulation of precipitation patterns over eastern China by sea surface temperature anomalies[J]. Journal of Climate, 30(17): 7 017-7 033. DOI URL