Numerical Study On The Vertical Transport Of Water Vapor By Deep Convection

The vertical transport of water vapor by deep convective process occurring in Darwin area over Australia and Naqu area over the Tibetan Plateau has been investigated using Weather Research Forecast (WRF) model with different cloud microphysical schemes and aerosol concentration. These simple results may help the future research to understand the influence of the climate change by the deep convective process.The simulated characteristics of the storm reveal good agreement with observations, such as the onset and location of convection and precipitation, when different deep convective processes were simulated by WRF model. Sensitivity experiments of cloud microphysical scheme has reached the following conclusions:(1) There are different characteristics of water vapor vertical flux with deep convective processes which occurring in different area, that is, when the convective cloud arises over Darwin area, the trend of upward flux of water vapor over convective region is: increase-decrease-increase-decrease with the altitude increasing, but the trend is increase-decrease with deep convective process arises over Naqu area. These trends are not sensitive to cloud microphysical schemes, but the water vapor flux density is sensitive to cloud microphysical schemes. A further analysis shows that these phenomena is correlated to the vertical updraft in the cloud. (2) Both the short-time humidifying effect on upper troposphere and duration are sensitive to cloud microphysical parameterization schemes, when deep convective process's humidifying effect on upper troposphere was investigated. Firstly, for tropical deep convective process, the largest difference of the maximum upper troposphere water vapor mixing ratio can reach to 17.2% with different schemes, for Tibetan Plateau deep convective process, the largest difference is 20.3%. Secondly, two deep convective processes both leading to humidifying effects duration ranging from one to few hours. (3) The variations of average upper troposphere humidity for 24h have decreased for two processes, but still more than 10%. The results of this study indicate that the uncertainty effect during the day time scale due to cloud microphysical scheme should not be neglected. So improving of cloud microphysical parameterization scheme is very important to the model assessment of climate.At the same time, we have set up three sensitivity experiments, including different initial cloud droplets number concentration, to investigate the effect on water vapor vertical transport by different background of aerosol. The result shows that:(1) The simulated characteristics of the storm for different experiments reveal good agreement with observations, such as the onset and location of convection and precipitation, but there are difference in the amount of precipitation, that is, the average amount of precipitation is reduced with initial cloud droplets number concentration increasing. (2) Initial cloud droplets number concentration change can leads to a large different effect on short-time hydration on upper troposphere by deep convective process, but the long-time hydration on upper troposphere is insensitive to the change of initial cloud droplets number concentration.