THE SUGGESTION AND IDEALIZED EXPERIMENTS OF VERTICAL VORTICITY DATA ASSIMILATION METHOD FOCUSED ON POTENTIAL TEMPERATURE GRADIENT

Abstract

 Analyzing storm genesis, which contains persistent and complex patterns of deep convection, is important for forecasting linear-shaped heavy rainfall several hours ahead. It is suggested that the baroclinic atmosphere in the localized region generated by the temperature and pressure gradients realizes deep convection. In this research, the data assimilation method of vertical vorticity was used to determine the effect of the baroclinic atmosphere on the initial values of model computations. First, applying the variational method enables us to obtain a diagnostic equation in which the equation of motion, conservation law of mass, and entropy are considered as constraints. Its formalism is applied to the observation operator for assimilation of the estimated vertical vorticity. Next, idealized experiments are used to clarify how the data assimilation method, represented above, affects the atmosphere in the model computations. As a result, the change in the potential temperature and vertical wind thorough the error covariance matrix generates coherent convection in the computations. Compared with the computation in which horizontally uniform vertical shear is applied to the initial state, the results of data assimilation are also similar to those from the viewpoint of the relationship between potential temperature distribution and convection.