1951～2010年云贵高原大理和丽江气温、降水的气候特征分析

Climatological Characteristics of Air Temperature and Precipitation at Dali and Lijiang in the Yunnan–Guizhou Plateau from 1951 to 2010

利用大理和丽江气象站1951～2010年的逐日气象资料,分析了横断山脉东部气温、降水的气候特征。结果表明,1991年以后,大理和丽江地区均存在显著增温的趋势(0.58和0.55℃/10 a),明显高于同时期中国平均气温的增加幅度;而在1991年之前,大理和丽江的年平均气温呈现下降或微弱上升的趋势(-0.14和0.07℃/10 a)。与夏季平均气温的增温幅度相比,冬季平均气温的增温更显著,且其变化趋势与年均气温的气候特征是一致的。大理和丽江年总降水及各季节降水量在1951～2010年并没有明显增加或减少的趋势。大理和丽江雨季开始的时间分别为第28候和第30候,持续时间分别约为5.5和4.5个月。20世纪80年代以后,丽江年平均风速的减小强度明显大于大理,这是因为丽江站地处城区,城市化剧烈,地表粗糙度增加显著。日照时数与云量呈反相的季节变化,降水量的多年平均的逐候变化与日照时数、总云量、尤其是低云云量相关,随风速增大而减小。

Using daily meteorological observations collected at Dali and Lijiang stations from 1951 to 2010,we analyze the climatological characteristics in the eastern part of Hengduan Mountains.The results show that the annual mean surface air temperature obviously has been increasing after 1991(0.58 and 0.55°C/10 a at Dali and Lijiang,respectively),and the increase is significantly larger than that for the entire China.However,the annual mean surface air temperature decreased at Dali and increased slightly at Lijiang(-0.14 and 0.07°C/10 a at Dali and Lijiang,respectively)before 1991.Compared with the range of mean temperature increase in the summer,the mean temperature increase in the winter is more significantly,and the trend of mean temperature change in the winter is consistent with that of annual mean temperature.There are no obvious changing trends of annual total precipitation and seasonal precipitation at Dali and Lijiang from 1951 to 2010.The rainy season for Dali and Lijiang starts from Pentad 28 and 30,respectively.The rainy season lasts for 5.5 and 4.5 months at Dali and Lijiang,respectively.Since the 1980s,the increase in annual mean wind speed at Lijiang is larger than that at Dali.This is because the Lijiang meteorological station is located at the urban area of Lijiang and the urbanization has led to large increase in the surface roughness.The seasonal variations of sunshine duration and cloud cover(including total cloud and low cloud)are opposite.The pentad-mean precipitation is correlated with sunshine duration and total cloud,especially low cloud,and decreases with increasing wind speed.