青藏高原地表温度时空变化分析

使用MODIS地表温度(LST)产品对青藏高原地表温度的空间分布和年际变化进行分析。通过一种融合时空信息的方法对LST缺失像元进行重建恢复,重建后有效像元比例达到97%以上。用正弦和线性分段函数法将4个瞬时时刻的LST观测值拟合为日平均LST,经地面0cm土壤温度观测数据验证,拟合后的均方根误差(RMSE)在1K以内。建立以年为周期的余弦函数模型,刻画了LST在一年内的季节波动,并得到LST的年平均值、振幅和峰值日期3个参数。分析了各参数在空间上的分布和多年的变化趋势。结果显示:LST年平均值与海拔高度、纬度和下垫面类型相关性较大;年内振幅从青藏高原东南部到西北部呈升高趋势;水体的峰值日期相比其他地物类型有明显的延迟。多年变化斜率分析显示,整个青藏高原的年平均LST以每年0.015K的速度升高,振幅以每年0.076K的速度增长,反映出受气候变化的影响,极端气候出现的概率明显增大,而峰值日期有所提前。

Changes in Land Surface Temperature over Qinghai-Tibet Plateau

The spatial distribution and multi\|year change in land surface temperature (LST) over the Qinghai\|Tibet Plateau (QTP) was analyzed using MODIS LST products.Firstly,the null pixels were reconstructed by integrating temporal and spatial information.The validity ratio of LST was showed to be over 97% after reconstruction.Secondly,a sine and linear piecewise function was utilized to fit the four instantaneous observations to mean daily LST.Ground observation of 0 cm soil temperature was employed to validate the fitting results,which the accuracy is within 1 K.Lastly,a cosine function model was built to describe the seasonal fluctuation of LST.The mean annual LST,the amplitude and the peak LST date were subsequently extracted by this model.Results showed that the mean annul LST was highly correlated to attitude,latitude and the type of underlying surface.Amplitude of LST was showed to rise from the southeast to northwest.The peak date of water was obviously delayed compared with other land cover types.Slope analysis showed that the mean annual LST over the QTP was increasing with a velocity of 0.015 K per year.Amplitude was elevated by 0.076 K per year,which indicated that the probability of extreme weather was larger than before,due to the greenhouse effect and climate change.The peak date of LST appeared earlier to some extent.