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 effects of lakes in Wuhan, the routine observation data of national stations around Wuhan Houguan Lake and the NCEP/FNL reanalysis data during 2013 to 2022 were used in this study. The WRF numerical model was applied to investigate the possible mechanisms of the impact of Houguan Lake on the surface meteorological elements in the lake area and the surrounding areas during the typical winter and summer months (January and July 2013) separately. The results are as follows. (1) In the typical winter month, the warming effect of Houguan Lake is significant, while in the typical summer month, the warming effect is weak. The Houguan Lake shows a cold lake effect during the daytime while a warm lake effect at night. The decrease in the daily highest temperature and the increase in the daily lowest temperature leads to a decrease in the diurnal temperature difference. (2) Both the average wind speed and average daily maximum wind speed in the lake area are increased by Houguan Lake. In the typical winter month, the region and magnitude of the average wind speed and daily maximum wind speed in the Houguan Lake area and downwind area increase significantly more than that in the typical summer month. (3) There is a limited "wet island effect" in Houguan Lake in both the typical winter and summer months. The relative humidity decreases with the increasing distance from the lake boundary. 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 shift of the wind direction in the lake area. The southeastern part of the lake is relatively larger and has a greater intensity and range of impact on temperature, wind speed, and relative humidity. In the typical winter month, Houguan Lake is affected by northerly airflow, which has a more significant impact on the temperature and relative humidity on the south shore of the lake. However, this feature is reversed in the typical summer month.