一个简单的热带有限区资料四维同化方案

根据广州区域气象中心热带有限区数值天气预报的条件和特点,设计了一个简单可行的四维同化方案,并通过模式平行试验,详细地分析了该方案对分析和预报的改进情况,表明该方案可以得到一个较为平衡而又与模式大气状态近于协调一致的分析场,大大缩短了模式的Spin—up时间和减小了积分初期模式调整的幅度,从而改进了预报结果。这种改进在资料稀疏区比资料密集区要大得多。通过四维同化,模式的高度场预报、风场预报、质量场及总动能在积分过程中的演变等都得到了令人满意的改进。通过在同化过程中区别对待20°N以南的资料稀疏区及其以北的资料密集区,进一步使模式降水预报得到显著的改进。

A SIMPLE TROPICAL LIMITED AREA FOUR-DIMENSIONAL DATA ASSIMILATION SCHEME

An uncomplicated four-dimensional data assimilation scheme is established, following the conditions and characteristics of tropical limited area NWP in Guangzhou Regional Meteorological Center. Parallel tests have been done to analyze in detail the impact of the scheme on the analysis and forecast. It is shown that, by the use of the scheme, the analysis is more equilibrated and approximately consistent with the model atmosphere, and the spin-up time of the model is greatly shortened and the amplitude of adjustment in the initial stage of model integration reduced , improving the forecast, The improvement is much more enormous in data-sparse area than in data-dense area. Forecasts of both height field and wind field are improved satisfactorily with the 4-D assimilation, and so are the evolutions of both mass field and total kinetic energy during the integration. By treating data-sparse areas south of 20°N differently from data-dense areas north of it, in the assimilation, rainfall forecast can be obviously improved as well.