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Abstract: Soil surface temperature and air temperature are essential indicators of climate change, and had received growing attention. In this paper, variations of soil surface temperature and air temperature in the mountainous region of southern Sichuan from 1981 to 2011 was analyzed. The study area is lying on the east edge of Qinghai-Tibet Plateau, China, and is very sensitive to climate change. In order to better understand the temperature change status of this region, the study area was divided into six areas (labelled fromⅠto Ⅵ area) based on landform, soil type and main land use, and the meteorological data including daily soil temperature at 0 cm and daily air temperature were used to analyze the regionalization variation of temperature. The meteorological data were obtained from eight local weather stations, including eastern district of Panzhihua and Huili County, Leibo County, Muli County, Xichang City, Yanyuan County, Yuexi County as well as Zhaojue County of Liangshan Yi Autonomous Prefecture, Sichuan Province. The spatial distribution of mean soil surface temperature and air temperature were analyzed by basic stats, the trends of the temperatures were revealed by simple linear regression, the abrupt changes were determined by cumulative sum anomaly detection method and signal-to-noise ratio, and finally, the relationship between soil surface temperature and air temperature was discussed. The results suggest that the mean annual soil surface temperature and air temperature in the mountainous region of southern Sichuan ranged from 15.6 to 20.5 ℃ and 12.2 to 17.2 ℃ respectively, presenting a spatial distribution pattern with high values in the southern part and valleys, and low value in the northern part and high mountains. Both soil surface temperature and air temperature had significant increasing trends on the annual and seasonal scale, whereas the increasing rate was higher in winter than that in summer which meant the seasonal variations were obviously different. In six types of areas, the type Ⅵ area which lies in high mountainous region had the highest warming trend which is 2-6 times of other areas, and the abrupt changes of soil surface temperature and air temperature occurred around 1990；the typeⅡarea which is located at the Anning River valley had the lowest temperature change and there was not any abrupt change. The soil surface temperature and air temperature showed extremely significant positive correlation (P<0.01),indicating that they have high consistency. However, the asymmetric warming phenomenon also existed between two temperature indexes. In the whole year and four seasons in the mountainous regions (type Ⅲ, typeⅤ and type Ⅵ areas) and in the spring of the Jinsha River valley (type Ⅰ area),soil surface temperature warming showed a much stronger trend than the air temperature warming, thus difference between soil surface temperature and air temperature (Ts-Ta) presented significant increasing trend and even had abrupt change occurred. The results would be helpful to provide reference for predicting drought and flood disasters and building climate models. Different from the previous study which only analyzed soil surface temperature or air temperature, this paper compared two temperature indexes, and found that the asymmetric warming phenomenon between them was significant (P<0.05),suggested that not only the variations of soil surface temperature and air temperature should be noted, but also the impact of changes in the relationship of Ts-Ta on the climate system needs to be concerned.

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