Abstract: Based on the air temperature data from 31 automatic weather stations (AWS) during June to August of 2012, the temporal and spatial characteristics of summer near-surface air temperature and the possibly controlling factors in the Beijing central business district (CBD) were analyzed. Air temperature from the AWS of CBD and from the national meteorological station at Chaoyang district of Beijing was compared. The results show that the spatial distribution of the near-surface air temperature in the CBD is directly affected by the difference of underlying surface types and anthropogenic heating. The mean monthly air temperature in summer of 2012 in the densely populated, high-rising buildings and asphalt surface areas is about 1.0 ℃ higher than that in the green coverage area in the CBD. Anthropogenic heat emission due to human activity and use of vehicles at night is the main reasons for large spatial differences of the urban heating environment, while its difference in the daytime is relatively small. The daily and weekly variations of air temperature are significant in the CBD and in Chaoyang weather station. The air temperature difference between them is a positive value regardless in the daytime or at night. Surface air temperature is higher in the CBD than in Chaoyang weather station in the daytime and at night, which suggests an extra urban heat island (EUHI) effect in the Beijing CBD. The daily variations of urban heat island and EUHI are similar. Under different weather conditions, intensity of EUHI effect is different. The EUHI effect is strong in a sunny day with breeze and partly cloud, especially at night, while is weak in a cloudy day with high humidity; it is the weakest in a rainy day. Sunshine and solar radiation is important to the EUHI. The spatial distribution of EUHI in the CBD is similar under the different weather conditions.

Key words: Central business district (CBD), Thermal environment, Anthropogenic heat, Extra urban heat island (EUHI) effect