近50年来中国季节性冻土与短时冻土的时空变化特征

在对中国冻土气象观测资料整理和分析的基础上, 研究了中国冻土分布的时空演变规律。主要分析了中国冻土分布的季节变化、冻土深度的空间变化, 以及冻结日期、解冻日期、冻结时间长度的空间分布特征, 同时也分析了以上各要素的时间变化特征。结果表明: 中国冻土分布广泛, 在我国东部的长江以北地区、西北地区及青藏高原地区均有分布; 其中季节性冻土具有显著的年内变化特征, 冻结一般从秋季开始, 冬末春初冻结的面积和深度达到最大, 春季逐渐开始融化, 夏季冻结的面积和厚度达到最小; 冻土的冻结过程和融化过程表现出各自不同的特征, 整个中国地区冻土的融化过程所持续的时间比冻结持续的时间长, 也更为复杂, 这与地形及土壤特性有着密切的关系; 近几十年来, 在全球变暖背景下, 中国冻土主要表现为最大冻土深度减小, 冻结日期推迟, 融化日期提前, 冻结持续期缩短, 以及冻土下界上升的总体退化趋势, 冻土的主要转型时期发生在20世纪80年代中期。

Characteristics of Spatial and Temporal Variation of Seasonal and Short-Term Frozen Soil in China in Recent 50 Years

Based on the quality control of daily meteorological observation data of frozen soil in China,the spatial and temporal variations of frozen soil have been investigated.The seasonal change of the frozen soil,the change of the frozen soil depth,the beginning dates and the ending dates are mainly analyzed.The results show that frozen soil occurs in most of the territory in China,including the north of the Yangtze River,Northwest China and the Tibetan Plateau.The monthly variation of seasonal frozen soil is significant.The freezing process generally began in autumn,and reached the maximum of depth and area in the end of winter.In spring the frozen soil began to thaw and finished in the summer. The thawing and freezing processes of frozen soil demonstrated different characteristics and the thawing process persisted longer and more complicatedly than the freezing process.This has a very close relationship with soil characteristics and topographic factors.In the background of global warming in the last few decades,the frozen soil showed a degradation in China.The maximum of frozen depth decreased,the beginning dates of soil freezing occurred later and the ending dates of soil freezing occurred earlier and the persisting of soil freezing shortened,as well as the soil base rose.It is in the mid 1980s that the significant abrupt change of the frozen soil happened.