2002—2020年青藏高原近地表土壤日冻融循环时空变化模式  

Spatio-temporal variation patterns of diurnal freeze-thaw cycles of the near-surface soil on the Qinghai-Tibet Plateau between 2002 and 2020

作　　者：沈麒凯 刘修国[1] 周欣[1] 张正加 陈启浩[1] SHEN Qikai;LIU Xiuguo;ZHOU Xin;ZHANG Zhengjia;CHEN Qihao(School of Geography and Information Engineering,China University of Geosciences(Wuhan),Wuhan 430074,China)

机构地区：[1]中国地质大学(武汉)地理与信息工程学院,武汉430074

出　　处：《地理学报》2023年第3期587-603,共17页Acta Geographica Sinica

基　　金：国家自然科学基金项目(41801348,41771467)。

摘　　要：青藏高原近地表土壤的日冻融循环极大地影响着土壤和大气之间的水分与能量交换,研究其时空变化模式对深入理解青藏高原生态环境的气候变化响应具有重要意义。本文基于MODIS、AMSR-E、AMSR-2遥感数据等资料,获取AMSR系列传感器在青藏高原的昼夜校准系数,利用Fourier非线性模型实现AMSR微波辐射产品与MODIS热红外地表温度产品的融合,生成每日1 km分辨率近地表土壤日冻融状态结果,开展2002—2020年青藏高原近地表土壤日冻融循环时空变化模式研究。结果表明:①相比于面向全球的校准方法,本文改进的AMSR系列传感器校准方法更适合于青藏高原地区。利用Fourier非线性模型融合后获得的土壤冻融产品在提升分辨率的同时日冻融判别精度达80.96%,相较于未融合结果准确性提高3.95%。②青藏高原近地表土壤季节性冻融过程中的日冻融循环发生天数空间上存在显著差异性,其中藏南区域与青海高原发生天数最高,时间上存在周期性,呈升温时向西北转移,降温时向东南转移。③2002—2020年青藏高原不同区域年内日冻融循环发生天数变化趋势不同,藏北高原、藏南高山及藏东区域呈增加状态,青海高原呈减少状态。④青藏高原连续日冻融循环起始时间点存在区域差异,总体上解冻过程中起始时间点由东向西逐渐推迟,冻结过程起始时间点由西向东逐渐推迟;2002—2020年近地表土壤连续日冻融循环起始时间点在解冻过程中提前0.17 d/a,冻结过程中提前0.18 d/a。The diurnal freeze-thaw cycle of near-surface soils on the Qinghai-Tibet Plateau(QTP)significantly affects the exchange of water and energy between the soil and the atmosphere,which is important for an understanding of the response of the QTP to climate change.Based on MODIS,AMSR-E and AMSR-2 data,we first obtained the diurnal calibration coefficients from AMSR-2 to AMSR-E in the Qinghai-Tibet Plateau(QTP),and then used the Fourier nonlinear model to fusion diurnal freeze-thaw index with surface temperature,and further obtained the diurnal freeze-thaw condition of near-surface soils at 1km resolution per day,and finally carried out a study on the spatial and temporal changes of diurnal freeze-thaw cycles of near-surface soils in the QTP between 2002 and 2020.The results indicate that:(1)The improved calibration method of AMSR series sensors in this paper is more suitable for the QTP region than the calibration method for global scale.The accuracy of the freeze-thaw product obtained by fusion using the Fourier nonlinear model was 80.96%for diurnal freeze-thaw discrimination,which was 3.95%higher than that of the unfused product.(2)The frequency of diurnal freeze-thaw cycles in the seasonal freeze-thaw process of nearsurface soils on the QTP varies spatially,with the highest frequency occurring in the southern Tibetan region and the Qinghai plateau,and is cyclical in time,the high frequency region shows a shift to the northwest when warming and to the southeast when cooling.(3)In the past20 years,the trend of diurnal freeze-thaw days in different parts of the QTP is varied,with the northern Tibetan plateau,southern Tibetan alpine region and eastern Tibetan region showing an increase and the Qinghai plateau showing a decrease.(4)There are regional differences in the beginning of the continuous diurnal freeze-thaw cycle on the QTP,with the beginning of the thawing process being gradually delayed from east to west and the beginning of the freezing process being gradually delayed from west to east.In the past 20 years,

关 键 词：青藏高原 日冻融循环 近地表土壤 多源遥感 AMSR MODIS 

分 类 号：S152[农业科学—土壤学]