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.
