【中文介绍】

        土壤湿度是陆气相互作用、农业、以及水资源调配方面非常重要，但是观测数据较为稀少，对于很多国家和地区（如中国）很难获得和广泛的使用。因此，很多研究采用将前期累计降水的异常作为土壤湿度的多寡的替代数据，但并没有具体的研究对这一替代的合理性和可靠性。本文收集整理1992-2013年中国大陆1000多站点称重法得到的每月三次、分为5层的土壤湿度数据，通过严格质量控制，得到732站点逐月数据，然后利用基于观测的土壤质地计算的土壤容重和田间持水量，将称重法得到相对湿度转换为便于使用的体积含水量，最后分析了土壤湿度时空变化特征，并研究了前期降水对土壤湿度的时空变化关系。主要结论：1）土壤湿度空间分布与降水相似，西北小，东南大；2）在同一地区土壤湿度随土壤深度增加；土壤湿度季节变化较小，春秋较大，夏季较小；3）从全国来看10，20，50厘米土壤湿度呈增加趋势；土壤湿度记忆随土层深度增加。4）在湿润区，超前1-2月的降水距平与土壤湿度距平相关显著，但是在干旱区二者的关系并不密切。5）本研究的一个重要产出是提供了长时间（22年，1993-2012年）、多站点（732）的观测土壤湿度资料为公众使用。

  【英文介绍】

        Based on the gravimetric technique measured soil relative wetness and the observed soil characteristic parameters from 1992-2013 in China, this study derives a user-convenient monthly volumetric soil moisture (SM) dataset from 732 stations for five soil layers (10, 20, 50, 70, and 100 cm). The temporal-spatial variations in SM, and its relationship with precipitation (Pr) in different subregions are then explored. The magnitude of SM is relatively large in south China and is low in northwest China, and it generally increases with soil depth in each region. The maximum SM appearing in spring and/or autumn, and the minimum is in summer, and the SM seasonality does not vary as distinctly as that of Pr. For the top three soil layers (10 cm, 20 cm, and 50 cm levels), the linear trend analysis indicates an overall increasing SM tendency, and the mean trends (averaged across stations with trends passing 95% significance level test) are 9.35e-07 cm3/cm3/year, 7.37e-03 cm3/cm3/year, and 2.45e-03cm3/cm3/year, respectively. SM memory depends on the soil depth and regions, and it in has longer retention time in the deeper layers. Furthermore, the correlation between SM and antecedent Pr varies with soil depth and lag time. The antecedent Pr anomaly (1 or 2 months in advance) can be used to some extent as a surrogate SM anomaly in most regions except for in arid regions. This result is further demonstrated by the relationships between SM anomaly and the standardized precipitation index. The current SM dataset can be used in various applications, such as validating satellite-retrieved products and model outputs.

  【关键图表】

图1 中国1992-2013年4-9月不同土深的站点平均含水量。其中，a）10厘米（732站），b)20厘米(732 站),c)50厘米(730站),d)70厘米(183站),d)100厘米(203站)  

 Figure 1 The mean volumetric soil water content (v, cm3/cm3) averaged over the growing season (April to September) from 1992 to 2013.The number of stations for a) 10 cm (732 stations), b) 20 cm (732 stations), for c) 50 cm (730 stations), d) 70 cm (183 stations), and d) 100 cm (203 stations) soil depth.
 

  【引用格式】       

      Wang A. and Shi X., 2019：A multilayer soil moisture dataset based on the gravimetric method in China and its characteristics. Journal of Hydrometeorology, 20: 1721-1736.