黑河流域表层土壤水分干化特征研究  

Characteristics of Surface Soil Moisture Drydown in the Heihe River Basin

作　　者：董世玉 朱忠礼 徐自为 刘绍民 柴琳娜 DONG Shiyu;ZHU Zhongli;XU Ziwei;LIU Shaomin;CHAI Linna(State Key Laboratory of Earth Surface Processes and Resource Ecology,Faculty of Geographical Science,Beijing Normal University,Beijing 100875,China)

机构地区：[1]北京师范大学地理科学学部,地表过程与资源生态国家重点实验室,北京100875

出　　处：《高原气象》2023年第3期771-784,共14页Plateau Meteorology

基　　金：中国科学院战略性先导科技专项(A类)(XDA20100101)。

摘　　要：土壤水分干化是指降水发生后土壤逐渐变干的过程,此过程一般包括重力排水、大气需求限制的蒸发以及水分限制的蒸发三个阶段,此三阶段在表层土壤中表现最为明显。黑河流域发源于祁连山中段,上中下游具有十分明显的景观地带性,探讨该地区表层土壤水分干化特征将为理解流域内不同环境下土壤蒸发的规律和影响因素提供理论支撑。本文基于2016-2020年黑河流域上中下游10个气象观测站点表层土壤水分、土壤温度、气温等资料,利用降水后的土壤干化事件分析了各区域土壤水分、潜在蒸散、归一化植被指数(Normalized Difference Vegetation Index,NDVI)和土壤质地等因素与表层土壤干化速率的关系,并使用指数模型拟合干化事件,总结了各站点干化速率的季节间变化规律。2016-2020年黑河流域10个站点共识别出362个有效干化事件,分析结果表明:(1)土壤进入干化期后,干化速率随土壤含水率降低而逐渐减缓,约12天后,上游、中下游站点土壤干化速率皆趋于稳定,上游站点稳定在约0.04 cm^(3)·cm^(-3)·day^(-1),中下游则趋于0。(2)上中下游表层土壤90%的蒸发效率分别低于0.25、0.15和0.12,无法满足大气需求,但若考虑土壤剖面5 cm以下的蒸散,其蒸发效率将接近1。(3)黑河上游表层土壤水分较高,土壤干化过程主要为大气需求限制阶段,中下游表层土壤水分较低,土壤干化过程为水分限制阶段。而就表层土壤蒸发速率而言,上游主要受大气水分需求影响,土壤蒸发速率随潜在蒸散的增加而增大,但当土壤水分超过0.4 cm^(3)·cm^(-3)时,潜在蒸散和土壤水分的变化对干化速率无显著影响;中下游主要受水分供应影响,土壤蒸发速率随土壤水分的增加而逐渐增大,潜在蒸散对土壤蒸发速率的影响不显著。(4)植被对表层土壤水分干化速率的影响与下垫面植被类型及土壤干湿状态有关,而土壤质地对The process of soil drying is referred to as soil moisture drydown.It usually occurs after precipitation,especially for surface soil,and we address this process in three dominant regimes:gravity drainage,energy-limited regime and water-limited regime.The Heihe River Basin originates from the Qilian Mountains,and the landscape zonality here is clear from its upstream,midstream and downstream.By exploring the characteristics of surface soil moisture drydown in this area,researchers were able to understand the patterns and factors associated with soil evaporation under different conditions.The soil drydown events were investigated using data on soil moisture,soil temperature,and air temperature collected between 2016 and 2020 from 10 meteorological observation stations located in the Heihe River Basin.The relationships between soil moisture(SM),potential evaporation(PE),the normalized difference vegetation index(NDVI),soil texture and surface soil drying rates were explored.Using the exponential model for fitting drydown events,the seasonal variation of the drying rate at each site was compared.Results showed that:(1)There were 362 effective drydown episodes between 2016 and 2020,totaling 3584 days.After entering the drydown stage,as the soil gradually became dry,the drying rate also slowed down and became stable after 12 days.The upstream site settled around 0.04 cm^(3)·cm^(-3)·day^(-1),whereas the middle and downstream sites tended to 0.(2)In upstream,midstream,and downstream,the values of surface soil moisture evaporation efficiency(90%)are lower than 0.25,0.15,and 0.12,respectively,which can only partially meet atmospheric demand.The evaporation efficiency may be close to 1 if the evapotranspiration of soil profiles below 5 cm is taken into account.(3)Because the surface soil in upstream locations of the Heihe River is relatively wet,the soil drydown process is limited by the atmosphere.The middle and lower reaches of the Heihe River are drier and limited by water.As for the surface soil evaporation rate,the u

关 键 词：土壤水分 干化 土壤蒸发 原位观测 黑河流域 

分 类 号：P461[天文地球—大气科学及气象学]