A Numerical Simulation of the Influence of the Large Scale Field on a Mesoscale Disturbance

摘要

A limited area model has been developed to study mainly the influence of the large scale field on a mesoscale disturbance. It has seven levels for height and horizontal velocity and six levels for vertical velocity, temperature and humidity. The interval between levels is smaller in lower atmosphere so that a low level disturbance can be effectively simulated.The data of 00GMT 23 May 1968 is chosen as the initial data of the simulation. A typical case of squall line generation was observed in the NSSL network a few hours later than that time.According to the preliminary experiment, the lateral boundary conditions proposed do not give rise to any artificial change in the total mass field and seem to be applicable to the initial field of our case.The simulated field in the main experiment, where the horizontal grid size is 47.7km at 60°N, is essentially of large scale. The position of the maximum value of the upward motion corresponds well to line storms observed and the upward motion seems to be an important factor in the generation and maintenance of the local line storms in this case.