初值精度对月预报影响的数值研究

NUMERICAL STUDY ON EFFECTS OF THE ACCURACY OF INITIAL FIELDS ON THE MONTHLY FORECAST

利用改进的 T42L10模式,以1992年8月31日12时为初始场,分别以瞬时初始场和平均初始场,作30天长期数值预报,以对比研究初值精度对月长期数值预报结果的影响.研究结果表明:(1)无论是高度场还是风场,瞬时初始场所作月预报的相关系数要比平均初始场的高约9个百分点.(2)从瞬时初值出发所作的500hPa 高度场及流场中,对东亚地区较深的槽,里海至乌拉尔较强的脊区,以及维持在东亚40°N 左右的急流都作了较好的模拟,而平均初始场的月预报结果与实况的差别较大.(3)用平均初始场所作的预报,其系统过于平滑,使预报结果受到影响.

Effects of accuracy of the initial fields on the monthly forecast are studied by em-ploying the improved T42L10 model,with the data of 12 GMT 31 August 1992 as theinitial field.A mean initial field,which is used in the contrast research of the monthlyforecast,is obtained by superimposing a certain disturbance on the initial field.The nu-merical results are as follows:(1) the correlation coefficients of the forecast made fromthe initial field are 9% higher than those according to the mean initial field;(2) in theforecasts of 500hPa height and wind fields made from the initial fields,the deep troughover the eastern Asia area,the ridge occupying the area from the Caspian Sea to the U-ral,and the jet maintaining in the 40°N in the eastern Asia are well simulated,whilethe forecasts made from the mean initial field can not be well simulated;and (3) the dis-turbance superimposed in the initial field evolves with time,and it will cause the exces-sive smooth of the forecast system.