镇江2009年盛夏极端异常气候分析及ECMWF模式检验

Analysis of extremely abnormal climate in midsummer of 2009 in Zhenjiang and ECMWF model verification

将2009年7月第5候至8月第2候作为研究时段,利用NCEP/NCAR再分析资料,对镇江地区2009年盛夏罕见的低温多雨寡照的极端异常气候作了诊断分析。在此基础上,对比分析了同期ECMWF的中期预报产品与实况,实现了对ECMWF模式的中期预报性能检验,由此加深了对此类天气过程中期预报的理解。结果表明：在研究时段内,西太平洋副热带高压异常偏东偏弱,110~120°E上空850 hPa层上存在异常南北风的辐合区,受西南季风和热带系统的共同影响,整层具有良好的水汽输送条件。在此次极端异常气候发生过程中,ECMWF对西太平洋副热带高压减弱东退、维持海上和增强西进的中期预报精准。同时,其数值产品对西风指数和850 hPa温度也具有良好的中期预报指示意义,成为准确预报此次过程的重要依据。

Taking the period from the 5th pentad in July to the 2nd pentad in August of 2009 as the time window,the diagnostic analysis of extremely abnormal climate in Zhenjiang is performed by using the NCEP/NCAR reanalysis data.The medium-range forecast products of ECMWF model have been analyzed in comparison with the observation.The results show that the subtropical high over western Pacific is abnormally weaker and is located eastward obviously.There is a convergence zone of the south and north winds over 110-120 °E at 850 hPa.Furthermore,because of the southwest monsoon and the tropical systems,there is sufficient water vapor transportation in the whole layer.During the process of this extreme climate anomaly,the medium-term forecast of the position of the western Pacific subtropical high by ECMWF model is quite accurate.For the medium-term forecast,the products of ECMWF model also make sense,especially to the zonal index and the temperature at 850 hPa.