Quality Control and Analysis of in Situ Soil Moisture Data in Yunnan

Soil moisture is a variable that plays a crucial role in the energy and mass exchange between the atmosphere and land, and it is often used as an environment factor and process parameter in meteorology researches. However, due to the diversity of climatological conditions and differences in measurement setup, the quality of the soil moisture measurement is highly variable, which may have a significant impact on the data accuracy. Therefore, appropriate quality characterization is desired.Based on soil moisture data of 37 stations of Yunnan in 2010-2014, the spectrum-based approaches are used to eliminate 3 kinds of abnormal data. The constant, spike and noisy, caused by saturation of the signal and unresponsive sensors, are screened out by procedures analysis on the time series. The data integrality is shown not good, especially at some stations in the northwest of Yunnan Province, where the instruments are newly set up. After the first instability period, the data quality gradually improves. Among all abnormal values, the proportion of constant is up to 97% in all stations. The distribution of stations containing more spike shows less distinct pattern.Compared to the related meteorological data, different soil types show different responses to the precipitation. Sandy soil shows quicker reaction to the precipitation, and the change of soil moisture is more significant as well. As the rainfall intensity increases, the rise of the moisture increases too. Loam soil shows continuous rise in the few hours after the rainfall, but the variation is rather weaker, and the deeper soil moisture changes relatively smoothly. Clayey soil has a weak relationship with precipitation, and the soil moisture descends more quickly in the deeper layer than other soil type. It's found that the rainfall intensity and the soil moisture rise are not simply positively correlated, the soil moisture rises less after downpour, and these responses need further research.