重庆市气温变化趋势及其可能原因分析

通过对重庆市1924～2007年的平均气温、平均最高气温、平均最低气温、极端最高气温、极端最低气温随时间变化特征进行分析发现:近84年来重庆市平均气温微弱变冷,与全国平均温度相比线性变化趋势存在一定差异;平均最高和平均最低气温、极端最高和极端最低气温的非对称性变化显著,最高气温的下降对平均气温的影响很大,平均最低气温除春季外增暖都非常显著,最低温度的增高对气温日较差减小的影响更明显.夏季副热带高压位置偏南,使得我国西南地区东部夏季降水天气增多、云量增加、日照时数减少,加之轻雾日数增多,可能是重庆市夏季最高温度持续下降的主要原因.冬季最低气温的显著升高主要是由于降水天气减少、云量增加和城市热岛效应所致.

The Trend of Temperature Variation and Its Possible Causes in Chongqing

Based on the data of mean temperature, mean minimum temperature, and mean maximum temperature, extreme maximum temperature, and extreme minimum temperature in Chongqing from 1924 to 2007, the character-istics of temperature variations are analyzed.The results show that the decrease in the mean temperature in Chongqing is slight in recent 84 years, and the linear trend of the temperature in Chongqing is different from the trend averaged over China The asymmetric changes of mean nunimum temperature and mean maximum tempera-ture, extreme maximum temperature and extreme minimum temperature are distinct. The decrease in the mean maximum temperature has obvious influence on the mean temperature.The mean minimum temperature in addition to that in spring has a more striking increase.The effect of the minimum temperature increasing on the diurnal tem-perature range decreasing is more obvious than others.The more southward western Pacific subtropical high in the past summers leads to the increase in rainfall and cloud fraction in summer, as well as the decrease in sunshine time in the eastern part of South-West China and the increase in light fog days. It may be the dominative reason for the persistent decrease in the maximum temperature in summer. The decrease in precipitation days, the increase in cloud cover, and the urban heat island effect are the main causes of the significant increase in mean minimum temperature in winter.