鲍媛媛. 2021. 2019年南海季风爆发异常偏早的机制分析[J]. 气象学报, (0):-, doi:10.11676/qxxb2021.023
2019年南海季风爆发异常偏早的机制分析
Mechanisms of the abnormally early onset of the South China Sea Summer Monsoon in 2019
投稿时间:2020-08-17  修订日期:2020-11-11
DOI:10.11676/qxxb2021.023
中文关键词:  南海季风 中高纬环流 孟加拉湾气旋“Fani” 海温异常
英文关键词:South China Sea Summer Monsoon, Middle and high latitude circulation, “Fani”,SSTA
基金项目:
作者单位E-mail
鲍媛媛 中国气象局国家气象中心 baoyy@cma.gov.cn 
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中文摘要:
      摘 要 用逐日资料分析2019年南海季风爆发的详细过程和异常偏早机制,结果表明,(1)南海季风爆发于5月6日,青藏高原和中南半岛热源较常年偏弱,对季风爆发无明显影响。(2)中高纬度环流中期变化过程中在青藏高原及附近形成为期两周的偏强的高压脊,冷空气势力弱,来自热带的暖平流以及青藏高原东部晴空辐射偏强等因素使其温度异常偏高,起到加速海陆热力差异季节转变进程的作用,对季风爆发至关重要。(3)孟加拉湾气旋 “Fani”北上及登陆后迅速减弱形成的残留低压的凝结潜热释放,“Fani”凝结潜热释放和气旋性环流增强诱发孟加拉湾西南季风爆发从而引起的西南季风暖平流输送, 因“Fani”而加强北跳的南亚高压反气旋环流的暖平流输送, “Fani”影响结束后西南季风与东亚冷槽后部回流辐合产生降水释放凝结潜热等因素,一步接一步,形成了加剧温度正异常的“接力”,最终导致南海地区温度梯度加大,越赤道气流加强,南海季风爆发。(4)El Nino及赤道西太平洋实时海温阶段性正异常增长使得西北太平洋副热带高压(以下简称副高)偏西偏强,本身不利于季风爆发;但其西端的偏东风在赤道印度洋与中高纬南下偏北气流辐合,并在赤道印度洋和孟加拉湾海温正异常阶段性增强的背景下得以强烈发展,生成孟加拉湾气旋“Fani”,并在北上过程发展成为台风,由此引起大气环流一系列变化,最终导致南海季风异常偏早爆发。
英文摘要:
      Abstract: Detailed process and mechanisms of the abnormally early onset of SCSSM in 2019 are analyzed using daily data. The results show that: (1) SCSSM broke out on May 6, and the heat sources of Qinghai Tibet Plateau and Indochina Peninsula are weaker than usual, and have little influence on the onset of SCSSM. (2) A two-week high-pressure ridge in Tibetan Plateau and nearby with prominent temperature positive anomalies by warm advection from the tropics accelerates the seasonal transfer process of land sea thermal difference and plays a very important role in the onset of SCSSM. (3)The latent heat of condensation by “Fani”and its residual low pressure after landing at northeastern Indian, Warm advection caused by southwest monsoon onset in Bengal induced by the release of "Fani" condensation latent heat and the cyclonic circulation, the warm advection by the anticyclone circulation of SAH which is strengthened by "Fani", condensation latent heat caused by convergence southwest monsoon and backflow of the east Asian cold trough and its precipitation, all of these, step by step, form a "relay" to strengthen the positive temperature anomaly, which eventually led to the increase of temperature gradient in SCS, resulting in strengthening of cross equatorial flow and the onset of SCSSM.(4) El Nino and periodic development of positive real-time SSTA in the equatorial western Pacific makes WNSPH stronger and more westward, which itself is not conductive to the onset of monsoon. However, the easterly winds at the western end of WNSPH forms a convergence with northerly winds from the middle and high latitudes, which developments strongly under the background of strong developing positive SSTA increase in the equatorial Indian Ocean and the bay of Bengal and forms “Fani”, which develops to a typhoon and lead to a series of circulation change, and finally switch on the unusual early onset of SCSSM.
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