| 中高纬度与热带大气的共同作用对江南4-6月低频降水的影响 |
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| 引用本文： | 谭桂容,王一舒.中高纬度与热带大气的共同作用对江南4-6月低频降水的影响[J].Acta Meteorologica Sinica,2016,74(3):335-351. |
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| 作者姓名： | 谭桂容 王一舒 |
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| 作者单位： | 南京信息工程大学气象灾害教育部重点实验室, 气候与环境变化国际合作联合实验室, 气象灾害预报预警与评估协同创新中心, 南京, 210044,南京信息工程大学气象灾害教育部重点实验室, 气候与环境变化国际合作联合实验室, 气象灾害预报预警与评估协同创新中心, 南京, 210044 |
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| 基金项目： | 国家自然科学基金项目(41475088)、国家公益性行业专项(GYHY20140622)、江苏省高校自然科学研究项目(13KJB170013、BK20131431)。 |
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| 摘 要： | 基于中国国家气象观测站的逐日降水资料、NOAA (National Oceanic and Atmospheric Administration)提供的逐日向外长波辐射资料和NCEP(National Centers for Environmental Prediction)/NCAR(National Center for Atmospheric Research)逐日全球再分析资料,采用非滤波法提取10-30 d低频降水及低频环流因子,分析了1979-2013年江南地区4-6月低频降水及其关联的大气环流特征,着重讨论了中高纬度与热带共同作用对低频降水的影响及可能机理。结果表明:(1)江南4-6月降水的第1模态呈现全区一致的变化趋势,其10-30 d低频降水方差贡献率在江南南部较大,部分区域可达20%。(2)降水的低频异常不仅与热带对流有关,还与中高纬度大气环流的变化显著相关。当东印度洋及印度尼西亚一带对流旺盛,中国上游欧洲至西伯利亚地区高纬度位势高度表现为显著的正异常,江南上空为负异常时,有利于江南低频降水。(3)中高纬度大气环流与热带对流共同作用影响江南4-6月低频降水:当热带对流旺盛区(抑制区)位于东印度洋及印度尼西亚海洋性大陆一带时,热带热源的非绝热加热引起显著的上升(下沉)运动,并激发经向罗斯贝波北传;同时高纬度欧洲至西伯利亚地区的位势高度负异常(正异常)向东向南传播,两者在江南上游叠加,低压(高压)底前部的西南风(东北风)有利于孟加拉湾对江南的水汽输送加强(减弱),对应江南地区整层水汽通量辐合(辐散),低频降水偏多(偏少)。
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| 关 键 词： | 江南低频降水 非滤波法 低频 热带-中高纬度共同作用 |
| 收稿时间： | 2016/1/26 0:00:00 |
| 修稿时间： | 2016/3/24 0:00:00 |
Combined effects of mid-to high-latitudes and the tropic on the low-frequency precipitation in Jiangnan from April to June |
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| TAN Guirong and WANG Yishu.Combined effects of mid-to high-latitudes and the tropic on the low-frequency precipitation in Jiangnan from April to June[J].Acta Meteorologica Sinica,2016,74(3):335-351. |
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| Authors: | TAN Guirong and WANG Yishu |
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| Institution: | Key Laboratory of Meteorological Disaster, Ministry of Education(KLME), Joint International Research Laboratory of Climate and Environment Change(ILCEC), Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD), Nanjing University of Information Science and Technology, Nanjing 210044, China and Key Laboratory of Meteorological Disaster, Ministry of Education(KLME), Joint International Research Laboratory of Climate and Environment Change(ILCEC), Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD), Nanjing University of Information Science and Technology, Nanjing 210044, China |
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| Abstract: | Based on gauge observations of daily precipitation in China, daily outgoing longwave radiation data from the National Oceanic and Atmospheric Administration (NOAA), and reanalysis data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR), a non-filtering method is applied to extract low-frequency signals of 10-30 days in the daily rainfall and atmospheric circulations. The daily low-frequency rainfall in Jiangnan during the period of April to June (AMJ) for 1979-2013 has been revealed in terms of its characteristics and associated large-scale circulations. Specifically, this study focuses on the combined effects of mid-to high-latitudes and the tropic. Results show that:(1) the first EOF mode of the AMJ rainfall in Jiangnan demonstrates a consistent variation over the entire region. The variance accounted by the low-frequency precipitation in southern area of Jiangnan is about 20%, which is larger than that in other areas; (2) low-frequency precipitation anomalies are significantly correlated with convective activities in the tropics and atmospheric circulation anomalies in the mid-to high-latitudes. When convective activities are located over the eastern Indian Ocean and Indonesia, positive geopotential height anomalies occur over the high-latitudes of Europe and Siberia areas, whereas the negative anomalies occur over Jiangnan with abundant rainfall; (3) the combined effects of mid-to high-latitudes and the tropics affect the low-frequency rainfall in Jiangnan. When active (suppressed) convective activities are located over the eastern Indian Ocean and Indonesia, the diabatic heating over the tropics causes significant ascending (descending) motions, and triggers northward propagation of the Rossby wave. At the same time, the negative (positive) geopotential height anomalies over Europe and Siberia propagate southeastward. These northward and southward propagating geopotential height anomalies superpose on the upstream of Jiangnan, leading to the formation of a low-pressure (high-pressure) center. The southwesterly (northeasterly) flows ahead of the cyclone (anticyclone) anomaly reinforces (weakens) the moisture transport from the Bay of Bengal, leading to convergence (divergence) of the vertically integrated moisture flux over Jiangnan and abundant (scarce) low-frequency precipitation in this region. |
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| Keywords: | Low-frequency precipitation in Jiangnan Non-filtering method Low-frequency Combined effects of mid-to high-latitudes and the tropic |
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