摘要
利用改进的T42L10月长期数值预报谱模式,以1992年8月31日国家气象中心日常客观分析资料为初始场,在模式中分别就考虑和不考虑地形两种情形对当年9月北半球环流形势进行了模拟预报,并对比分析研究了地形作用对月际长期数值预报效果的影响。改进的T42L10谱模式考虑了较完整的物理过程,同时具有以下特点:(1)非线性平衡方程初值化和σ面上模式初值精度的提高;(2)改进了模式诊断云和模式水汽场方法;(3)超长波和低纬预报的改进;(4)考虑海温和下垫面状态在月预报中随预报时效的变化。结果表明:考虑地形时模式500 hPa高度场月预报平均的倾向相关系数在整个北半球范围内比不考虑地形时高0.08,可达0.73,模式预报的均方根误差月平均比对应的尢地形情形低10 gpm以上,同时低于对应的持续性预报误差;在东亚地区这种效果更为显著,预报的500 hPa月半均u,v场在考虑地形作用后也有一定的改善。考虑地形作用时预报的高纬极涡、中纬槽脊分布及低纬副高位置和强度均接近实况;去掉地形后预报效果显著下降,高纬极涡分离,中纬波动明显减弱,低纬副高减弱且位置偏南。进一步分析发现,由于地形作用,在青藏高原背风坡地区和台湾海峡一带可以分别形成显著的较大范围的气旋性环流和反气旋环流,对我国天气、气候以及北半球的大气环流产生重要影响。
In this paper, a numerical research of the influence of orography on the monthly numerical prediction has been made by comparison of the different simulations of the northern hemispheric circulations in September 1992 with and without incorpora tion of the orography, utilizing the improved T42L10 monthly numerical prediction model. The results show that the model forecasts turn out to be better if the orographic effects are considered. The correlation coefficient between the predicted with orography and the observed northern hemisphere 500 hPa geopotential height anomaly can arrive at 0.73 which is 0.08 higher than that without orography when with the orography, the forcasted averaged root mean square decreases by 10 gpm. The orographic effect appears more obvious in East Asia. The predicted 500 hPa circulations with orography is in good agreement with the observed. When the orography is removed from the model, the forecasts deviate a lot from the observed. The polar vortex centre splits and the fluctuations in the mid-latitude weaken apparently and the subtropical highs weaken and locatesd far south. We also find a cyclogenesis on the lee side of the Tibetan Plateau and an anticyclogenesis over the Taiwan in a large area due to the orographic effects of the Tibetan Plateau.
出处
《高原气象》
CSCD
北大核心
1995年第3期296-304,共9页
Plateau Meteorology
