| 亚洲热带夏季风的首发地区和机理研究 |
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| 引用本文： | 钱永甫,江静,张艳,姚永红,徐忠峰.亚洲热带夏季风的首发地区和机理研究[J].Acta Meteorologica Sinica,2004,62(2):129-139. |
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| 作者姓名： | 钱永甫 江静 张艳 姚永红 徐忠峰 |
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| 作者单位： | 南京大学灾害性天气气候研究所,南京,210093 |
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| 基金项目： | 国家自然科学基金面上项目“南亚高压和亚洲季风相互作用及其机制研究”( 4 0 175 0 2 1)，国家自然科学基金重点项目“江淮梅雨的年际和年代际变化及其机理研究”( 4 0 2 3 3 0 3 7) |
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| 摘 要： | 文中分析了多年逐候平均 85 0hPa风场和黑体辐射温度等物理量的时空演变 ,结果表明 ,90°E以东的孟加拉湾、中南半岛和南海是亚洲热带夏季风首先爆发的地区 ,爆发时间在 2 7～ 2 8候 ,具有突发性和同时性。 90°E以西的印度半岛和阿拉伯海是热带夏季风爆发较晚的地区 ,季风首先在该区 10°N以南爆发 ,时间约在 30～ 31候 ,然后向北推进 ,6月末在全区建立 ,爆发过程具有渐进性。机制分析表明 ,由于 110～ 12 0°E的中高纬东亚大陆在春季和初夏地面感热通量、温度和气压的迅速变化 ,使热带低压带首先在该处冲破高压带 ,生成大陆低压 ,并引导西南气流在 90°E以东地区首先建立。在 90°E以西的印度半岛地区 ,地面感热通量在 4～ 5月间几乎没有明显变化 ,因而印度季风比南海季风晚爆发约 1个月。由此得出 ,90°E是东亚夏季风和南亚夏季风的分界线。此外 ,还着重探讨了南亚高压的季节变化与亚洲热带夏季风爆发的时间联系。发现南亚高压中心位置与亚洲热带夏季风爆发时间有较好的对应关系。南亚高压中心跳过 2 0°N时 ,南海夏季风爆发 ,跳过 2 5°N时 ,印度夏季风在其南部爆发。将用上述方法确定的爆发时间与用其他方法确定的爆发时间相比较 ,发现它们在南海地区有较好的一致性 ,在印度地区略有差异。
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| 关 键 词： | 亚洲热带夏季风 南海季风 印度季风 机理分析 南亚高压 |
| 收稿时间： | 2003/7/23 0:00:00 |
| 修稿时间： | 2003年7月23日 |
THE EARLIEST ONSET AREA OF THE TROPICAL ASIAN SUMMER MONSOON AND ITS MECHANISMS |
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| Qian Yongfu,Jiang Jing,Zhang Yan,Yao Yonghong and Xu Zhongfeng.THE EARLIEST ONSET AREA OF THE TROPICAL ASIAN SUMMER MONSOON AND ITS MECHANISMS[J].Acta Meteorologica Sinica,2004,62(2):129-139. |
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| Authors: | Qian Yongfu Jiang Jing Zhang Yan Yao Yonghong and Xu Zhongfeng |
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| Institution: | The Institute of Severe Weather and Climate, Nanjing University, Nanjing 210093;The Institute of Severe Weather and Climate, Nanjing University, Nanjing 210093;The Institute of Severe Weather and Climate, Nanjing University, Nanjing 210093;The Institute of Severe Weather and Climate, Nanjing University, Nanjing 210093;The Institute of Severe Weather and Climate, Nanjing University, Nanjing 210093 |
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| Abstract: | The spatial and temporal feat ures of the multi yearly pent ad mean 850h Pa wind fields and the TBB fields were analyzed. It was found that the tropical Asian summer monsoon (TASM) onsets simultaneously and abruptly first over the wholearea in the Bay of Bengal (BB), the Indo-China Peninsula (ICP) and the South China Sea (SCS), east of 90°E, in the 27th to 28th pent ads of a year (pentads 3 to 4 in May) and therefore the whole area is the source area of the TASM;while the tropical Indian summer monsoon (TISM) onsets f irst in the south part of the India Peninsula (IP) and the Arabian Sea (AS) in the 30th to 31st pent ads. Then it advances gradually northward and onsets in the whole area w est of 90°E, by the end of June. Possible mechanisms were carefully analyzed and it was found that the rapid seasonal variations of the surf ace sensible heat flux, the air temperature and the surface pressure in spring and early summer in the middle to high latitudes of the East Asian continent between 110°E and 120°E is crucial responsible to the earliest onset of the South China Sea summer monsoon (SCSSM). It is the rapid warming that induces a continental depression to form and break throug h the high system of pressure originally located in the above continental areas. The low depression in turn introduces the south westerly to come int o the BB to the SCS areas, east of 90°E, and thus makes the SCSSM burst out first in Asia. In the IP area, west of 90°E, the surface sensible heat flux does not change almost during Apr. and M ay, the T ISM onset s lat er than the SCSSM by about 1 month. Therefore, it is concluded that the meridian of 90°E is the demarcation line between the South Asian summer monsoon (SASM, i. e. the TISM) and the East Asian summer monsoon (EASM, including the SCSSM). The relations of the onset time of the tropical summer monsoon to the seasonal changes of the South Asian High (SAH) at the 200 h Pa level are emphatically discussed. It was found that the SAH center position has close relation to the onset time of the tropical monsoon. When the SAH center crosses 20°N, the SCS summer monsoon onsets and when it crosses 25°N the Indian summer monsoon begins in the south part. By comparison of the sodetermined onset time with that determined by other methods, it is seen that they are in good consis tence in the SCS area, however, they are some what different in the IP area. |
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| Keywords: | The tropical Asian summer monsoon The SCS summer monsoon The India summer monsoon Mechanism analyses The South Asian High |
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