The control models are the standard mm4 using the blackadar high resolution boundary scheme , the bulk boundary scheme , the kuo cumulus parameterization scheme and explicit clouds 閉合處理湍流擴散問題,分別以原mm4中有云和無云的水份處理方案作為控制方案。
The results of numerical experiments , using the four - dimensional variational data assimilation system of the nonhydrostatic mesoscale model mm5 , show that : the tangent linear model and adjoint model conducted by keeping the " on - off " switches the same as the basic state , can provide a good approximation of the first - order information to the nlm perturbation and a good descent direction for the minimization procedure ; switching on and off at every other time step in the kuo cumulus parameterization scheme do n ' t impact the convergence rate of cost function ; the existence of the switches do n ' t impact improvement to the mm5 model rainfall prediction because that not only specific humidity , but also wind , temperature and pressure are assimilated into the model 非靜力中尺度數(shù)值模式mm5的四維變分資料同化系統(tǒng)進行的數(shù)值試驗結(jié)果表明: “開關(guān)”變量保持與基態(tài)一致,所構(gòu)造的切向線性模式能夠提供關(guān)于非線性模式擾動的一階近似,伴隨模式所計算的梯度值能夠為最小化過程提供較好的下降方向;郭氏降水參數(shù)化方案中對流每隔一個積分步的交替發(fā)生并不影響目標函數(shù)最小化的收斂速度; “開關(guān)”變量的存在也不影響將風(fēng)、溫度、氣壓和比濕結(jié)合起來同化對mm5降水預(yù)報準確性的提高。
The results also show that the precipitation forecast of the system is very sensitive to cumulus parameterization scheme , planet boundary layer ( pbl ) scheme and radiation scheme . for smaller meshes , the grell cumulus parameterization scheme is better than the other three cumulus parameterization schemes that are also tested in the experiments 數(shù)值模擬試驗結(jié)果還顯示,模擬降水預(yù)報對積云參數(shù)化方案、邊界層參數(shù)化方案、輻射參數(shù)化方案等比較敏感;在網(wǎng)格比較小時, grell積云參數(shù)化方案優(yōu)于本文試驗的另外三種積云參數(shù)化方案。