P-σ坐标系区域气候模式对冬夏季月平均场的模拟试验

NUMERICAL SIMULATION OF MONTHLY MEAN FIELD IN SUMMER AND WINTER BY A LIMITED AREA MODEL WITH P σ INCORPORATED COORDINATE

在钱永甫等（１９８５）研制的Ｐσ混合坐标系原始方程模式的基础上，发展了一个有限区域的嵌套细网格数值模式，并首先用于区域气候的模拟试验．利用ＧＦＤＬ１０年的月平均资料做嵌套，分别对１月和７月的气候平均场做了模拟，模拟的雨带及气压系统的位置和强度与实际场基本一致，模式较准确地再现了冬，夏季的区域气候特征。

The numerical model with so called p σ incorporate vertical coordinate was originally developed by Qian et al.and has been proven to have good performances either in numerical simulations or in forecasting experiments.Considering detailed nonadiabatic physical processes contained in this model,a one way nested fine mesh limited area model was developed and firstly used to simulate regional climatic fields,expected to be a useful RCM to simulate and predict short range regional climate changes.The physical processes are the same as in the former version except that the momentum,heat and moisture fluxes in the planetary boundary layer are computed with the similarity theory,the grid size is reduced to 1°×1° in the spherical coordinate system,the moisture is predicted at every time step instead in every hour.To test the predictability of RCM,this model was nested with GFDL data to simulate monthly mean fields of January and July with the tendency relaxation technipue in the outer 5 boundary cycles with the relaxation weight coefficients integrations of 0.0,0.4,0.7,0.9 and 1.0 from the boundary inward ,respectively.Time integrations with 45 day length are conducted from the mid of the corresponding previous month to the end of the month.The last31 day mean is taken as the January or the July climate.The model domain is from 10°N to 45°N and from 90°E to 135°E.The initial conditions and the boundary forcing are both taken from the GFDL monthly mean fields.The results show that the model relatively well simulates the positions and intensities of rain zones and pressure systems except for the overestimating of rairlall amount in January experiment,the northward movement of the rainfall belt in summer is also fairly simulated,therefore this model has certain capacity to simulate the regional climate and can be used as a regional climate model.The model's performance in simulating pressure systems in January experiment is better than that in July experiment.The tests also indicate that the lateral boundary condition is important to the regional climate modeling,in present simulation,pseudo rainfall offen takes place near the outflow boundaries and needs to be removed by further improvements of the lateral boundary condition.