Study of the coupling of cumulus convection parameterization with cloud microphysics and its influence on forecast of typhoon

The two-way interactions between cloud microphysics and cumulus convection are introduced into the Relaxed Arakawa-schubert Scheme (SAS) convection scheme, the improved scheme is tested with a typhoon case and, the forecasts are compared with those of the original SAS scheme. The results show that the track forecast is improved obviously after the inclusion of interactions between convection and large-scale environments while the influence on intensity forecast is not so evident. The grid-scale explicit precipitation gets much stronger and the sub-grid scale precipitation is reduced after coupling convection with cloud microphysics, with the impact on large-scale temperature and humidity also revealed based on the NCEP reanalysis data. A series of experiments are implemented to test the sensitivity of the different treatments of the convective snow, the different cloud-base conditions and the entrainment of snow and rain with the result that 72 h forecast is not sensitive to these factors. The improvement of the revised scheme on typhoon track forecast is reliable as shown by the statistical results from many cases.