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气象:2018,44(6):737-751
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MJO对我国降水影响的季节调制和动力-统计降尺度预测
吴捷,任宏利,许小峰,高丽
(南京信息工程大学大气科学学院,南京 210044; 中国气象局国家气候中心气候研究开放实验室,中国气象局-南京大学气候预测研究联合实验室,北京 100081; 中国地质大学环境学院大气科学系,武汉 430074; 中国气象局,北京 100081; 中国气象局数值预报中心,北京 100081)
Seasonal Modulation of MJO’s Impact on Precipitation in China and Its Dynamical-Statistical Downscaling Prediction
WU Jie,REN Hongli,XU Xiaofeng,GAO Li
(College of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing 210044; Laboratory for Climate Studies and CMA-NJU Joint Laboratory for Climate Prediction Studies, National Climate Centre, CMA, Beijing 100081; Department of Atmospheric Science, School of Environmental Studies, China University of Geoscience, Wuhan 430074; China Meteorological Administration, Beijing 100081; CMA Numerical Prediction Centre, Beijing 100081)
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投稿时间:2018-04-08    修订日期:2018-05-11
中文摘要: 利用1981—2016年中国区域CN05.1格点降水资料和EAR-Interim再分析资料,研究了季节循环对于热带大气季节内振荡(MJO)对我国降水影响的调制作用,并基于模式对MJO的预报建立了针对延伸期降水的动力-统计降尺度模型。结果表明,MJO对我国季节内降水异常的影响明显受到季节循环的调制。当MJO对流在热带印度洋活跃时,我国降水偏多的区域随季节由南向北推进;当MJO对流位于海洋性大陆地区时,在秋、冬季我国东部和高原大部分地区降水异常偏少,而到了春、夏季该关系反转。MJO对流和基本气流(特别是副热带西风急流)的位置和强度的变化所引起热带外环流响应的不同是造成这种季节性差异的重要原因。模式检验表明,BCC_AGCM2.2对目标候MJO的预报技巧可达18 d以上,在此基础上利用模式预报MJO信息构建了随季节演变滚动的MJO动力-统计降尺度预测模型。独立样本检验表明,该模型在较长时效(10~20 d)下对MJO高影响区低频降水异常的预报技巧高于模式的直接预报,特别是在MJO活跃时期对降水预报技巧的提升更加明显,这为MJO信号释用提供了新的思路。
Abstract:Based on the China regional grid precipitation dataset CN05.1 and EAR-Interim reanalysis data, the seasonal modulation of the impact of Madden-Julian Oscillation (MJO) on China’s precipitation anomaly is studied, and a dynamical-statistical downscaling model which focuses on extended-range precipitation forecast is established based on the MJO prediction by numerical model. The results show that the impact of MJO on precipitation anomaly is modulated by seasonal cycle obviously. When the MJO convection is active in tropical Indian Ocean, the above normal precipitation area advance northward along with the changes of seasons. When the MJO convection is active in the maritime continent, precipitation in eastern China and Tibet Plateau is abnormally less in autumn and winter, but this situation is gradually weakened or even reversed in spring and summer. The position and amplitude variation of MJO convection and basic state (especially the subtropical westerly jet) lead to different extra-tropical circulation responses, which are the main causes for these seasonal variations. The model verification suggests that the prediction skill of target pentad RMM index based on BCC_AGCM2.2 can extend to 18 days. In addition, a seasonal rol-ling MJO dynamical-statistical downscaling precipitation prediction model is established based on the forecasted RMM indices by dynamical model. The independent sample tests show that the dynamical-statistical model achieves higher skills in predicting the low-frequency precipitation anomaly than the direct output of BCC_AGCM2.2 in MJO high impact area during long lead time (10-20 d). The improvement is more obvious in the MJO active period. These findings could provide new thoughts for the MJO interpretation.
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基金项目:国家重点基础研究发展计划(973计划)(2015CB453203)、国家自然科学基金项目(41505065、41775066、41375062)和公益性行业(气象)科研专项(GYHY201406022)共同资助
引用文本:
吴捷,任宏利,许小峰,高丽,2018.MJO对我国降水影响的季节调制和动力-统计降尺度预测[J].气象,44(6):737-751.
WU Jie,REN Hongli,XU Xiaofeng,GAO Li,2018.Seasonal Modulation of MJO’s Impact on Precipitation in China and Its Dynamical-Statistical Downscaling Prediction[J].Meteor Mon,44(6):737-751.