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Dynamics and Predictability of Troposphere-Stratosphere Dynamical Coupling during Stratospheric Sudden Warming Events

平流层突然变暖事件期间对流层-平流层动力耦合的动力学和可预测性

基本信息

批准号：
15340155
负责人：
MUKOUGAWA Hitoshi
金额：
$ 10.5万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2006
项目状态：
已结题

项目摘要

In this study, we obtained the following results on the dynamics and the predictability of the stratosphere-troposphere dynamical coupling during stratospheric sudden warming (SSW) events by examining 1-month ensemble forecast dataset provided from the Japan Meteorological Agency (JMA) and long-term global analysis datasets as well as performing a series of numerical experiments based on atmospheric general circulation models and the operational numerical weather forecast model of the JMA :1.The occurrence of SSWs with rather simple time evolution, such as a SSW in December 2001, is predictable at least 2 weeks in advance. The predictable period of such SSWs is at least two times longer than that of the tropospheric circulation.2.Sensitivity to the initial condition for the forecast of SSWs becomes very high during the onset period of the SSWs.3.The importance of the tropospheric blocking for the precursory event of the SSW is statistically confirmed. Prediction experiments also indicate that the tropospheric circulation anomaly associated with the blocking specified for the initial condition actually causes the subsequent SSW. The stratospheric circulation nonlinearly responds to the magnitude of the specified anomaly.4.The downward migration of the zonal-mean zonal wind anomaly after the SSW is predictable at most 1 week in advance. The downward migration is caused by the E-P flux convergence associated with zonal wavenumber (WN) 2 planetary waves propagating upward from the troposphere. The propagating property of WN 2 components strongly depends on the profile of the zonal-mean zonal wind around the tropopause region in high latitudes.5.Predictable period of SSWs with relatively complicated time evolution such as a SSW in January 2004 is at most 9 days.6.Forecast skill of the stratospheric annular mode tends to be improved for winter seasons when the variability of the stratospheric annular mode becomes large.

本文通过对日本气象厅(JMA)提供的1个月集合预报资料和全球长期分析资料的检验，以及基于大气环流模式和JMA业务数值预报模式的一系列数值试验，得到了以下关于平流层突然变暖(SSW)事件期间平流层-对流层动力耦合的动力学和可预报性的结果：1.时间演变较简单的SSW的发生，如2001年12月的SSW，至少提前2周就可以预测。这类SSW的可预报周期至少是对流层环流的两倍。2.SSW的预报对初始条件的敏感性很高。3.从统计上证实了对流层阻塞对SSW前兆事件的重要性。预报试验还表明，与初始条件指定的阻塞有关的对流层环流异常实际上是导致随后的SSW的原因。平流层环流对特定异常强度的响应是非线性的。4.SSW后纬向平均纬向风异常的下移最多提前一周可预测。这种向下迁移是由于从对流层向上传播的纬向波数(WN)2行星波的E-P通量辐合引起的。WN 2分量的传播特性强烈依赖于高纬度对流层顶区的纬向平均纬向风廓线。5.时间演变相对复杂的SSW(如2004年1月的SSW)的预报周期至多为9天。6.当平流层环模的变率变大时，平流层环模的预报技巧在冬季趋于提高。