Numerical simulation study on local climate effects of Houguan Lake in Wuhan

The roles of urban inner lakes in changing the urban ecology and human living environment are significant, to study the local climate effect of lakes in Wuhan, based on the routine observation data of national stations around Wuhan Houguan Lake and the NCEP/FNL reanalysis data, the WRF numerical model was used to carry out the possible mechanisms of the impact of Houguan Lake on the surface temperature, wind speed, relative humidity and precipitation in the lake area and the surrounding areas during the typical months (January and July 2013) in winter and summer separately. The results are as follows: (1) In the typical months of winter, the warming effect of Houguan Lake is significant, while in the typical months of summer, the warming effect is weak. The Houguan Lake shows a cold lake effect in the daytime and a warm lake effect at night, and the decrease of the daily highest temperature and the increase of the daily lowest temperature lead to the decrease of the diurnal temperature difference. (2) The average wind speed and average daily maximum wind speed in the lake area are increased by Houguan Lake. In the typical months of winter, the region and value of the average wind speed and daily maximum wind speed in Houguan Lake area and downwind area increase significantly greater than that in the typical months of summer. (3) There is a limited "wet island effect" in Houguan Lake in both typical months of winter and summer. The relative humidity decreases with the increase of the lake boundary distance. Houguan Lake has a small impact on precipitation in the lake area and surrounding areas. (4) The temperature difference between the lake and the land leads to the diurnal conversion of the wind direction in the lake area. The size of the lake and the changes of environmental wind field are closely related to the local climate effects of the lake. The southeastern part of the lake is relatively larger, which has a greater intensity and range of impact on temperature, wind speed and relative humidity. In the typical months of winter, Houguan lake is affected by northerly airflow, which has a more significant impact on the temperature and relative humidity on the south bank of the lake. In the typical months of summer, this feature is reversed.