利用资料诊断和全球大气原始方程模式(Intermediate General Circulation Model,IGCM),研究了2008年1月中国南方地区出现罕见的持续性雨雪事件的成因。结果表明,2008年1月大气非绝热加热场的主要异常出现在热带海洋、青藏高原及中亚地...利用资料诊断和全球大气原始方程模式(Intermediate General Circulation Model,IGCM),研究了2008年1月中国南方地区出现罕见的持续性雨雪事件的成因。结果表明,2008年1月大气非绝热加热场的主要异常出现在热带海洋、青藏高原及中亚地区以及北大西洋。用全球异常热源强迫IGCM得到的对流层中低层环流场异常和再分析资料结果十分接近,说明非绝热加热异常和该事件密切相关。分区试验的结果显示青藏高原以及中亚地区的加热异常是导致此次事件的主要原因,中高纬度北大西洋上的海温异常也有一定贡献。前者在中国南方产生了中低层的异常南风气流和贡献率约为95%的异常垂直上升运动,加强了向中国南方的水汽输送;后者加强了北大西洋涛动正位相,能导致12%的垂直运动异常和相对于观测偏弱的环流异常。另一方面,虽然赤道中部太平洋La Ni a事件对应的热汇有利于此次事件的发生,但是热带太平洋La Ni a型海温分布的综合效应对此次事件的贡献为负,贡献率约为-27%。展开更多
A dipole pattern of summer precipitation over the mid-high latitudes of Asia, which is characterized by opposing summer precipitation variations between the Mongolian and Northeast China(MNC) region and the West Siber...A dipole pattern of summer precipitation over the mid-high latitudes of Asia, which is characterized by opposing summer precipitation variations between the Mongolian and Northeast China(MNC) region and the West Siberian Plain(WSP), is found to be clear and stable on both interdecadal and interannual scales during 1981–2011. Spring snow cover anomalies over a small region within the WSP and the Heilongjiang River(HR) region are closely related to the variation of this dipole mode during the subsequent summer, and they can therefore be considered as forecasting factors. Our statistical results imply a potential process explaining the relationship between the spring snow anomalies and the summer rainfall dipole. Corresponding to the snow anomalies, Rossby waves propagate along a path from the WSP region, via the Mongolian Plateau, to the Stanovoy Range during summer. At the same time, Rossby-wave energy divergences and convergences along this path maintain and reinforce an anomalous cyclone and anticyclone pairing over the Asian continent, which is significantly linked to opposite summer precipitation anomalies between the MNC and WSP regions. Numerical experiments are needed to further confirm the above conjecture and demonstrate the detailed physical mechanisms linking the spring snow cover anomalies and summer precipitation dipole.展开更多
文摘利用资料诊断和全球大气原始方程模式(Intermediate General Circulation Model,IGCM),研究了2008年1月中国南方地区出现罕见的持续性雨雪事件的成因。结果表明,2008年1月大气非绝热加热场的主要异常出现在热带海洋、青藏高原及中亚地区以及北大西洋。用全球异常热源强迫IGCM得到的对流层中低层环流场异常和再分析资料结果十分接近,说明非绝热加热异常和该事件密切相关。分区试验的结果显示青藏高原以及中亚地区的加热异常是导致此次事件的主要原因,中高纬度北大西洋上的海温异常也有一定贡献。前者在中国南方产生了中低层的异常南风气流和贡献率约为95%的异常垂直上升运动,加强了向中国南方的水汽输送;后者加强了北大西洋涛动正位相,能导致12%的垂直运动异常和相对于观测偏弱的环流异常。另一方面,虽然赤道中部太平洋La Ni a事件对应的热汇有利于此次事件的发生,但是热带太平洋La Ni a型海温分布的综合效应对此次事件的贡献为负,贡献率约为-27%。
基金the joint support of the National Natural Science Foundation of China (Grant No. 41375090)the Basic Research Fund of the Chinese Academy of Meteorological Sciences (Grant No. 2013Z002)the International Cooperation and Exchange of the Ministry of Science and Technology of China (Grant No. 2009DFA21430)
文摘A dipole pattern of summer precipitation over the mid-high latitudes of Asia, which is characterized by opposing summer precipitation variations between the Mongolian and Northeast China(MNC) region and the West Siberian Plain(WSP), is found to be clear and stable on both interdecadal and interannual scales during 1981–2011. Spring snow cover anomalies over a small region within the WSP and the Heilongjiang River(HR) region are closely related to the variation of this dipole mode during the subsequent summer, and they can therefore be considered as forecasting factors. Our statistical results imply a potential process explaining the relationship between the spring snow anomalies and the summer rainfall dipole. Corresponding to the snow anomalies, Rossby waves propagate along a path from the WSP region, via the Mongolian Plateau, to the Stanovoy Range during summer. At the same time, Rossby-wave energy divergences and convergences along this path maintain and reinforce an anomalous cyclone and anticyclone pairing over the Asian continent, which is significantly linked to opposite summer precipitation anomalies between the MNC and WSP regions. Numerical experiments are needed to further confirm the above conjecture and demonstrate the detailed physical mechanisms linking the spring snow cover anomalies and summer precipitation dipole.
