Analysis and Verification on the Causes of the Higher Nighttime Temperature at Jingmen National Meteorological Observatory

Since Jingmen National Meteorological Observatory (hereinafter referred to as Jingmen Station) moved to the new location in 2008, there has been a significant higher nighttime temperature compared to the surrounding meteorological stations. An analysis of data from Jingmen Station and its neighboring station from 2012 to 2021 revealed that the higher temperature often occurred in seasons other than summer, most pronounced between October and December. The highest frequency of higher temperature was seen at night, but it was rarely captured during the daytime. From 2012 to 2021, the annual number of days of temperature difference ≥ 2 ℃ was 48－151, and the maximum temperature difference between the two stations could reach 8.4 ℃. The increased temperature difference was accompanied with the reduced wind speed. The temperature difference between the two stations was larger in westerly wind than in other wind directions. The temperature was most likely to be higher under the clear sky. According to the main weather characteristics derived from the statistical analysis, the nocturnal clear-sky radiative inversion was responsible for the phenomenon of higher temperature. Radiative inversion is highly likely to occur on nights with low wind speed, clear sky, and low atmospheric vapor content. This causes the temperature at Jingmen Station, located on the mountaintop, to be higher than that at stations in the plain areas. Moreover, when there is a westerly wind, the urban heat island effect can enhance the temperature difference between the two stations. Finally, the conclusion is verified by performing an unmanned aerial vehicle (UAV) boundary layer vertical sounding experiment, which rules out the possibility of the influence of the heat sources to the north of Jingmen Station.