Improvement of microphysical and dynamical parameterization of Ogura and Takahashi’s numerical thunderstorm model

Abstract

Cloud models can play a key role in interpreting observational evidence to estimate the potential for successful cloud seeding experiments. Among different types of cloud models, one-dimensional cloud models with bulk water microphysical parameterization are very useful. Therefore in this paper, a one-dimensional Ogura and Takahashi (O-T) cloud model with bulk parameterization has been discussed for studying the possibility of improvement in microphysical processes in applying for cloud seeding experiments. The most important features of the new model could be defined as the inclusion of Kessler Parameterization (PMZ) in a warm rain process, Bigg's freezing PMZ, and terminal velocities of rain water and hail particles. The model has been run for various cases, Kessler PMZ, Kessler PMZ and Bigg's freezing, and Kessler PMZ, Bigg's freezing, and Lin PMZ. Strong modifications were noticed in the rainfall profile, with Kessler PMZ rain started later due to the necessity of cloud droplets to initiate formation. Rainfall became heavier due to the accretion of cloud droplets and raindrops. With Bigg's freezing, due to the enhancement of the freezing process rate, the second peak of rainfall intensity vanished. With Lin terminal velocities of rain and hail, due to the accumulation of rain water near the surface, the updraft became weaker, while downdraft became stronger. Due to the above mentioned improvements, the rainfall pattern of the improved model became heavier and sharper in a shorter time and is in good agreement with the behavior of occurrence of natural showers