The Numerical Study Of A New Microphysics Scheme Based On The Regional Microphysical Properties Over East Asia

Based on the long–term observations over East Asia, a new two–moment bulk microphysics scheme(temporarily called the Wang–Yin scheme hereafter in this paper) that is suitable to the simulation and forecast of weather in the East Asia region has been developed, via improving some physical processes, such as particle size distribution and particle activation. The Weather Research and Forecasting(WRF) model coupled with the Wang–Yin scheme is used to simulate a mixed rain–snow storm occurred in early November 2012 over North China. Simultaneously, in order to test the Wang–Yin scheme, experiments have been performed using the five other sophisticated schemes as control experiments. To verify the validity of the Wang–Yin scheme, surface observations, Doppler radar observations, and FY–2E and NASA GOCCP satellite observations are used to test the simulation results. This new scheme is referred to as the Wang–Yin scheme in this paper.The results show that,(1) the Wang–Yin scheme is able to describe the precipitation characteristics, such as the rain belt distribution and precipitation intensity. The distribution of solid precipitation forecast in the Wang–Yin scheme experiment agrees with the observation better than in other runs. And the prediction of rain rate in the Beijing station by the Wang–Yin scheme is better than other 5 schemes, in aspects of both the precipitation intensity and development. Skill scores also show that the Wang–Yin scheme has good prediction capability, though the TS and ETS scores are lower than the Goddard and Morrison schemes in the magnitude of moderate rain.(2) Numerical simulations show that the differences between microphysics schemes have inconspicuous impacts on the prediction of atmospheric circulation. At the height from surface to 900 hPa, the content of vapor predicted by the Wang–Yin scheme is weaker than that by other schemes, and from 900 h Pa to 400 hPa, vapor content prediction in the Wang–Yin scheme run is 3%–5% larger than other runs. In the Wang–Yin scheme experiment, the max value center of liquid hydrometers appears at the height of 2 km, according to the statistical result of the vertical cloud structure in East Asia.(3) Besides, in the aspects of spatial distribution of solid precipitation and temporal evolution of precipitation rate, the Wang–Yin scheme has obvious advantage over the other schemes. The Wang–Yin scheme accurately reproduced the vertical mixed–phase distribution characteristics, vertical structure and evolvement features of the nephsystem, and the simulations of the microphysical processes accord with the recent studies of ice clouds precipitation. The results above show that the Wang–Yin scheme is able to predict the precipitation and the internal microphysical processes accurately, that indicate the rationalization and veracity of the improvements and adjustments in the Wang–Yin scheme.On the base of these conclusions, in this paper, sensitivity experiments are processed to simulate a warm section heavy precipitation occurring in the Southern China region from 7 to 8 May 2013. Results of numerical tests show that,(1) Under the premise that the air density on ground is constant(0? ?101325.0/(287.05*298.0)), the Ferrier mass–weighted fall speed expression has some advantages over the Locatelli fall speed, but differences between this two runs are not obvious. And the temporal distributions and development tendencies of the two precipitation predictions are similar, indicates that the mass–weighted fall speed expressions in cloud microphysics schemes impacts the precipitation prediction by influencing the vertical distribution and flux of ice–phase water substances.(2) Spectral shape parameters of cloud microphysical partials have significant impacts on the precipitation intensity and development. The results of sensitivity experiment show that the spectral shape parameters improved by Yin based on the cloud microphysical characters of East Asia has obvious advantages over the constant parameters. The false precipitation prediction is alleviated in the sensitivity run with improved spectral shape parameters.(3) In this warm section heavy precipitation occurring in the Southern China region, options of spectral shape parameters impact the rainfall prediction more obviously than the options of mass–weighted fall speed. And the Ferrier + Yin combination is the best microphysical option combination in this simulation.This paper preliminarily indicates that the sophisticated microphysics parameterizations, such as the Lin scheme and the Goddard scheme, have good applicability in the prediction of weathers in East Asia. And it also shows that the Wang–Yin scheme has some advantages in the predictions of precipitation and the forecast of cloud microphysical characteristics. On this base, we can see the further studies on the regional cloud microphysical characteristics in East Asia are indispensable, and the developments of the regional cloud microphysics scheme are essential to the development of Chinese numerical weather prediction(NWP) techniques.