Trends of MODIS land surface temperature trend from 2000 to 2011, Yakutia, Siberia

For the land surface temperature trend analyses we used the MOD11C3 MODIS LST product configured on a 0.05° latitude/longitude MODIS Climate Model Grid (CMG) raster, which is a monthly composited average representing clear-sky LST values in °C. The monthly LSTs were analyzed over the 11 year interval from May 2000 to April 2011. Linear trend calculations for the 11 year interval were performed separately for each bi-monthly mean value in each grid cell, using the least squares method. We decided to use two-monthly intervals since the timing of thawing and freezing vary from year to year and do not necessarily occur over just one month in the year, or in the same month each year. We used a student t-test to calculate the significance of each trend, based on the assumption that there was no relationship between the date and the trend (null hypothesis). Similarly, we also calculated the trend of the mean annual LSTs.

本研究针对地表温度（Land Surface Temperature, LST）趋势分析，采用了配置于0.05°经纬度MODIS气候模型网格（CMG）栅格的MOD11C3 MODIS LST产品。该产品为月度合成平均值，表征晴空条件下的地表温度，单位为摄氏度。本次分析的月度地表温度数据时间跨度为2000年5月至2011年4月，共计11年。针对该11年时间区间，我们采用最小二乘法，对每个栅格单元内的每一双月平均值分别开展线性趋势计算。之所以选用双月时间间隔，是因为每年的解冻与冻结节点存在年际差异，未必仅集中在单个月份，亦不会每年固定出现在同一月份。我们基于“日期与趋势之间不存在关联”的原假设（零假设），采用学生t检验计算各趋势的显著性水平。类似地，我们同时计算了年度平均地表温度的变化趋势。