利用2008—2020年自动气象站逐小时气温观测资料,研究了乌鲁木齐市主城区气温日变化特征。结果表明：乌鲁木齐市主城区日最高气温主要出现在14:00—17:00,日最低气温出现在05:00—08:00。同一季节内,各月的日最高气温出现时次最大相差1 h;日最低气温出现时次在冬季各月间的差异较大,12月和1月的日最低气温出现时间与2月相差4 h。此外,12月和1月的日最低气温出现时间比其他月均早2~3 h,与我国其他城市存在较大差异。乌鲁木齐市主城区各月的最高气温出现频率的日分布曲线以“双峰”型为主,主峰时次为15:00—18:00,次峰时次为21:00,夏季和冬季各月的日最高气温各时次出现频率的时间分布较为集中,春季和秋季相对分散。最低气温出现频率的日分布曲线在春、夏、秋三季均呈“单峰”型,冬季峰值特征不明显。春、夏、秋3季的最低气温在07:00—10:00的出现频率较高,冬季12月和1月在20:00的出现频率相对较高。主城区09:00—12:00的1 h正变温较大;18:00—22:00的1 h负变温较大,正负变温存在不对称性,1 h变温是乌鲁木齐市主城区变温的主导者。乌鲁木齐市主城区冬季气温的日变化特征比其他3个季节更为复杂。

Cities are critical on the earth’s surface because of human activities. Cities significantly influence regional climate change and the ecological environment. Recently, with the rapid development of China’s urbanization process, the impact of urbanization on temperature change has attracted increasing attention. Urumqi is the capital of Xinjiang Uygur Autonomous Region, China. With the rapid urbanization development, the diurnal temperature change characteristics in the main urban area of Urumqi are unclear. To deeply understand the diurnal temperature characteristics in Urumqi, this study used hourly temperature observation data from the Automatic Weather Station from 2008 to 2020 to analyze the diurnal temperature variation characteristics over urban Urumqi. The results show that the maximum high temperature in the main urban area of Urumqi occurs at 14-17 o’clock, and the lowest temperature occurs at 05-08 o’clock. In general, the daily minimum temperature reaches its lowest value around sunrise, which occurs earlier in summer than in winter. In the main urban area of Urumqi, the daily minimum temperature in December and January occurs at 5:00 and 7:00 in the summer, inconsistent with the general rule of daily temperature change and different from the daily temperature change characteristics in other cities in China. The temperature shows a sharp increase but a slow decrease during the day. Analysis of the temperature change rate in different time intervals shows that the sharpest change occurs in one hour. The statistical pattern of minimum temperature occurs from 06 to 10 o’clock in spring, summer, and autumn. The statistical pattern of minimum temperature occurs at 20 o’clock in December and January, which is a special phenomenon in Urumqi, where the time at which the maximum positive temperature is more concentrated than the negative temperature. The diurnal variation of winter temperature in the main urban area of Urumqi is more complex than in the other three seasons. Forecasting winter temperature in Urumqi City is always challenging. The forecast accuracy of winter temperature in Urumqi is low, significantly affecting meteorological services. This study provides the daily temperature variation characteristics in the main urban area of Urumqi, which could help weather forecasters to deepen their understanding of the refined temperature characteristics in the main urban area of Urumqi and provide a useful reference for practical forecast business. Because this study only analyzes from the perspective of data statistics, the causes of special diurnal variation characteristics of winter temperature in the main urban area of Urumqi must be further studied using numerical simulation and other methods.