Abstract:
“75.8" heavy rain is a disaster, which caused a large loss to the soci
ety. Many meteorologists have done a lot of research works of this event, and pa
id much attention to the predictability.“75.8"heavy rain in Henan Province was
particularly chosen for the study of the mesoscale ensemble forecast.
Two experiments were implemented. The first one especially focused on the relati
ons between cumulus convective parameterizations and the heavy rain. For this pu
rpose, the KainFristch ETA scheme was chosen. The interaction between the trig
g
er function and the mass flux calculations in large scale environment was taken
into consideration. Some empirical factors have been perturbed in a reasonable r
ange to construct the ensemble members to describe the uncertainty of model. The
results indicate that different factors in cumulus convective parameterization
have different impacts on the precipitation. The location of the rainfall is les
s influenced by different factors, but the intensity of the heavy rain is improv
ed, the precipitation forecasted by ensemble mean increased by 30%. Meanwhile, d
ifferent factors would have different impacts on the time when the convection ha
ppens, the rainy duration as well as the development of convection. The second e
xperiment adopted different resolution of model and multiparameterization to f
o
rm ensemble members. The results prove that the ensemble mean would improve the
intensity forecast to some extent. Compared with the results coming from model w
ith high resolution, the precipitation forecasted by ensemble increases by 20%-3
0%. Ensemble forecast would decrease the uncertainties from the model itself. Th
e differences among various cumulus convective parameterizations, empirical fact
ors and model resolutions indeed have a certain impacts on the simulated results
of model.