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

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℃/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℃/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.