Numerical Study Of Sea Breeze Circulation And Cloud Water Pattern Over The Hainan Island

In this study, the 3D high resolution numerical simulation of sea breeze circulation and cloud water pattern in cloudy condition over the Hainan Island is examined by using WRF model, coupled with Noah land-surface model firstly. The results show that WRF is capable to capture the sea breeze circulation on July 5, 2012. Formed at 12:00 BST over the whole island, sea breeze is strong during 15:00～18:00 BST. Sea breeze front is stronger and sea breeze circulation can last for a longer time due to the blocking and lifting effects of the mountains. Besides, valley breeze forms and disappears almost along with the sea breeze. On the one hand, it results in frontolysis of sea breeze when the valley breeze strengthens; otherwise it causes frontogenesis of sea breeze when valley breeze weakens. On the other hand, circulation becomes more pronounced when valley breeze overlaps with sea breeze. Moreover, clouds can be easily triggered under the convergence of the sea breezes or sea breeze front in the case, the convergence zone of sea breeze is the main potential precipitation area.Secondly, the numerical simulation of sea breeze circulation and its response to radiation parameterization of topographic effects are examined by using Weather Research and Forecasting (WRF) model. Terrain slope, aspect of slope and topography shading directly affect the solar zenith angle after employing radiation parameterization of topographic effects and then surface solar shortwave radiation changes. Usually the solar zenith angle of slope back to the sun is smaller than slope face to the sun, at the same time, less solar shortwave radiation is accepted at the foot of ubac after considering the influence of topography shading. So the second part is aimed to know the change of sea breeze circulation and cloud water pattern after using radiation parameterization of topographic effects and the possible reasons for the difference. The results are as follows. The exchanges of momentum, heat and energy between atmosphere and earth make meteorological parameters change. It is radiation parameterization of topographic effects that makes the simulated surface temperature more realistic, which also improves the ability of simulation of humidity. Simulated wind direction and speed are not obvious in two tests. Slope irradiance parameterization has different effects on upslope wind and sea breeze around the steep mountain which may strengthen sea breeze and weaken upslope wind sunward side, whereas the opposite back to the sun. So the pattern and intensity of sea breeze change significantly in mountain areas.