中国土壤湿度的垂直变化特征

使用中国 57个站 1981～ 2 0 0 0年 0～ 10 0cm的土壤湿度资料 ,逐站进行了垂直方向土壤湿度的诊断分析 ,根据湿度的垂直分布形态归纳为 3种主要类型 :夏季均匀型、急剧变化型和季节差异型 ;分析土壤湿度的年际变化发现 :多数测站湿度的距平符号在垂直方向是一致的 ,变化趋势以长时间持续干和湿以及 3～ 4a振荡周期为主 ;进一步对干和湿期土壤湿度和降水量进行合成 ,发现湿期和干期的土壤湿度垂直分布多数情况下保持了气候态的基本特征 ,湿期减干期的土壤湿度差与降水差有很好的对应关系

VERTICAL CHARACTER OF SOIL MOISTURE IN CHINA

Towards the vertical characteristics of soil moisture, a series of analyses were carried out, based on the moisture data of layer 0-100 cm soil collected at 57 meteorological stations from 1981-2000 in China. According to the distribution o f moisture alon g the vertical direction, the changes in soil moisture can be categorized into 3 types: (1) summer vertical uniformly distributed, rapid vertically changing, a nd se asonally differencing type. The main characteristics of the first type are low m oisture in summer seasons and relative uniformity in distribution, as well as ce rtain differences in vertical direction in the spring and fall seasons. This ty pe is mainly seen in Xinjiang and Ningxia Autonomous Regions, the east of Gansu and Henan provinces, where the soil is loam or sand soil; (2) The rapid vertic ally changing type locates in areas known as moisture jumping layer (defined as the l ayer where perennially existing the largest vertical difference in soil moisture ), which the moisture in the top is smaller than the bottom layer.Based on the density of vertical gradients and relative depth, there are three subgroups, whi ch are large upper vertical gradient, large middle and lower vertical gradient, as well as uniformly distributed vertical gradient. This type is mainly di stributed in Guangxi Autonomous Regions, Intersection area of Yellow River and H uai River, and some areas in the Northeast China where different upper and lower soil layer are found; (3) Seasonally differencing type, appears mai nly in northern areas where the soil is frozen during the winter seasons. Althou gh this type is characterized by larger soil moisture in middle and upper layers during the winter seasons, the depth of the high-humid layer differs from soil in different areas and with different compositions. When analyzing the depth /time sections of the soil moisture anomalies, signs of the moisture anomalies tested at most observation stations are vertically consi stent, signs are the reverse of the upper and lower layers in some stations. The changing characteristics here were represented by long-run consistent dry or hu mid, as well as 3-4a cyclical trends. When integrating the soil moisture and pre cipitation during dry and humid periods , the vertical distribution is found to remain in its original climate state at most observation stations. And there exi sts a well-defined corresponding relationship between the difference of moisture and the difference of precipitation for dry and humid periods.