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A multilayer soil moisture dataset based on the gravimetric method in china and its characteristics[2020-07-16]
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.
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.