Numerical Simulation Of The Impact Of Coastal Urbanization On The Advancement Of Sea Breeze Front In Hainan Islan

In this paper,the mesoscale model WRF-ARW（V4.0）is used to simulate a typical sea breeze front case in Hainan Island under different weather conditions with high numerical resolution,aiming to explore the three-dimensional structure and evolution characteristics of sea breeze fronts in different weather conditions over the region.Secondly,by designing sensitivity experiments on local urbanization,the article focuses on analyzing the impact of coastal urbanization in Hainan Island on the advancement of sea breeze fronts and the possible influencing mechanisms.The result shows:（1）Regardless of whether it is s clear sky or cloudy weather,the difference of sea breeze front structure caused by urbanization is the result of the combined influence of dynamic and thermal effects.After the expansion of urban land use,on the one hand,the urban heat island circulation and the high roughness of the urban underlying surface hinder the inland penetration of sea breeze,weaken the wind speed of the northwest humid and cold sea breeze,and cause the sea breeze front to be relatively lagging.On the other hand,the high sea-land thermal difference caused by urbanization enhances the convergence of sea breeze and the instability of the lower atmosphere,increases the wind speed of sea breeze by 1-2 m·s^-1,increases the thickness of sea breeze circulation by 100 m,and generates stronger vertical updraft in the front of sea breeze front.（2）The impact of urbanization on sea breeze front advancement is different under different weather conditions.Under clear skies,at the initial stage of the development of the sea breeze front,the thermal difference between the sea and the land has a driving effect on the sea breeze front;the friction effect hinders the advance of the sea breeze front inland,so the sea breeze front has no obvious effect on its advancing.During the strong development stage of the sea breeze front,the strong urban heat island circulation hinders the advance of the sea breeze front inland,which reduces the inland infiltration distance of the sea breeze front by about 5 km.Compared with the clear sky,the thermal difference between sea and land is relatively small in cloudy weather.In the early stage of the development of sea breeze front,the friction effect is stronger than the driving effect of the thermal difference between sea and land,which makes the sea breeze front lag 2 km.At the stage of strong development of the sea breeze front,the urban heat island is relatively weak,and the new infiltration distance of the sea breeze front lags behind,only 3.5 km.（3）The friction effect of the urban underlying surface reduces the average wind speed in the lower layer of the island,and weakens the cooling and humidifying effects in the region passing by the sea breeze front.（4）When the land use type is changed to urban,the net radiation and the exchange energy decrease,resulting in a significant decrease in the latent heat flux,sensible heat flux value and boundary layer increase.No matter in clear sky or cloudy sky,the change of energy is basically the same,but in clear sky,the energy release and absorption rate is significantly faster,and the boundary layer height also changes little due to the weak background field.