Abstract:
On basis of selecting reference stations by using a relatively objective standard, this paper analyzes the influence of urban heat island (UHI) intensity (
IUHI) on spatial and temporal temperature characteristics in a high temperature process of Beijing from 2 July to 6 July 2010, by applying hourly data of high density automatic weather stations and NCEP reanalysis data. The maximum temperature (
Tmax) during the process is more than 35.0 ℃ for each day, and the five-day mean
Tmax breaks the records at Beijing Weather Station since 1951. Continental warm high pressure controls most parts of China in the high-temperature process, and Beijing is in front of the high-pressure ridge. Major causes for the high-temperature process in Beijing are strong subsidence and the fohn effect of the northwesterly flowing over the Taihang Mountains. Affected by UHI effect, the distribution of the
Tmax, minimum temperature (
Tmin), and mean temperature (
Tmean) exhibits a high-temperature area in the center of the city, with the mean
IUHI gradually decreasing from the within fourth-ring area to the fifth-sixth-ring areas. The
IUHI of
Tmin is obviously larger, reaching 2.93 ℃, 1.87 ℃, and 1.43 ℃, respectively, for the central urban area, fourth-fifth-ring area, and fifth-sixth-ring area. The
IUHI of
Tmax is smaller, although the temperatures are as high as 1.45 ℃, 0.96 ℃, and 0.72 ℃, respectively, for the three urban zones mentioned above. The night
IUHI high values within the fourth ring during 3-6 July are more than 3.00 ℃, and the maximum
IUHI reaches 5.50 ℃ in the early morning on 6 July. The daytime
IUHI is relatively small, and the
IUHI shows a negative value in the morning of 2 July likely because the heating rate at reference stations is greater than that in the urban areas. The
IUHI diurnal variation of the three urban zones is nearly synchronic, and is characterized by a steadily strong
IUHI stage from 2100 LST to 0500 LST and a steadily weak
IUHI stage from 0800 LST to 1800 LST, with the periods of 0500-0800 LST and 1800-2100 LST undergoing a rapid decline and increase of the
IUHI, respectively. Therefore, the UHI effect has a marked influence on the strength and spatial distribution of the single extreme high temperature event in the urban area of Beijing.