An innovative method for measuring the hysteresis effects of soil moisture on meteorological variables at various time scales and climate conditions

Understanding the feedback and reactions of soil moisture to meteorological factors in meteorological-hydrological processes is essential due to the growing importance of soil moisture in energy and water cycles in critical zones. Using soil moisture and meteorological data from 1984 to 2018, based on Mann-Kendall and Sen slope trend, two possible patterns of land-atmosphere interaction were discovered in the Yangtze River Basin (YRB), low soil moisture model with less precipitation and higher evapotranspiration, and high-temperature mode with less soil moisture and less evapotranspiration. To measure the hysteresis between soil moisture and precipitation, temperature, and evapotranspiration, a novel method named Three-Step Method was put out. The lag times were measured at ground stations spread across various climatic zones and timescales. The findings demonstrated that the lag times are generally controlled by the regional climate, with shorter lag times in drier regions. Both long-term and short-term responses were seen in soil moisture to meteorological variables. On a monthly scale, soil moisture correlated positively with precipitation but negatively with temperature and evapotranspiration. On an annual scale, precipitation (temperature, evapotranspiration) lagged by roughly 0 to 2 months in the upper and middle regions and by -2 to -6 months in the lower region of the YRB. The contribution rates of meteorological elements on soil moisture were enhanced by taking lag time into account. This study provides a unique perspective for better understanding climate process forecasts and related drought management by considering the hysteresis of soil moisture on the feedback and responses of climate variables.

Automated summary

Understanding the feedback and reactions of soil moisture to meteorological factors is important in meteorological-hydrological processes. This study found two patterns of land-atmosphere interaction, as well as the influence of regional climate on the lag times. The results showed that soil moisture has both long-term and short-term responses to meteorological variables, with positive correlation with precipitation but negative correlation with temperature and evapotranspiration. The contribution rates of meteorological elements on soil moisture were enhanced by considering the lag time.