全球大气环流模式BCC_AGCM2.0.1对1998年夏季江淮流域强降水过程的回报试验研究

Hindcast for the 1998 Summer Heavy Precipitation in the Yangtze and Huaihe River Valley Using BCC_AGCM2.0.1 Model

利用中国气象局北京气候中心全球大气环流模式(BCC_AGCM2.0.1)对1998年6月24日～7月3日发生在我国江淮流域的强降水天气过程进行了回报试验。模式起报时间为1998年6月24日00时,使用前10天NCEP-II再分析逐时温度、涡度和散度场进行预报前初始协调(spin-up)积分,产生模式初值,预报时段为1998年6月24日～7月10日,回报试验结果表明:模式对全球500hPa位势高度的天气尺度演变过程具有4～7天的可预报性;BCC_AGCM2.0.1模式对中国区域的降水以及大气环流场具有3～4天的可预报性,6月24日起报后3天内的预报降水区域位置与实况一致,但中心强度有所差异。对起报后未来2天的5mm和10mm以上的降水预报能力相对较强,ETS评分值达到了0.25以上,HK评分超过了0.4,降水区域范围预报较为准确,BIA评分趋于1.0。模式对20mm以上的降水也具有一定的可预报性,但模式对大于30mm以上强降水的预报能力较差。

A hindcast for the heavy precipitation events occurring in the region of the Yangtze River and the Huaihe River in China from 24 June to 3 July 1998 was performed using the Beijing Climate Center Atmospheric General Circulation Model version 2.0.1 （BCC_AGCM2.0.1） of China Meteorological Administration.The BCC_AGCM2.0.1 model was run from 0000 UTC 24 June to 10 July 1998.The model initial values were generated by using the hourly temperature,vorticity,and divergence of NCEP reanalysis data to spin up for 10 days integration before the beginning of forecast.The results of hindcast experiment show that the predictability timescale of the 500-hPa geopotential heights over the whole globe is about 4-7 days,and that for the circulation field over China about 3-4 days.The spatial distribution of forecasted rainfall regions over China is nearly coincident with the observation during the first 3 days after initial forecast time,but the rainfall intensity has some regional differences between the hindcast and the observation.The predictability for forecasted daily precipitation at different thresholds is tested using BIA,ETS,and HK scores.In the 2 days of forecast,the BCC_AGCM2.0.1 model has high predictability for the daily precipitation above 5 mm and 10 mm,and the ETS score is above 0.25,the HK score above 0.4,the BIA score close to 1.0.But for the daily precipitation larger than 20 mm,the model has less predictability.