An Analysis of the Two-Way Interactions Between Soil Moisture and Precipitation Based on Observed Daily Data in Illinois from 2003-2014

Abstract:

The role of soil moisture in the climate systems has drawn much attention in the research of climate modelling and observational studies, yet the mechanisms of soil moisture (SM) influences on subsequent precipitation (P) have not been established due to polarising research findings from numerical models and observed data analyses. This study attempts to provide observational evidence of the SM-P feedback based on the state-average of 11-year (2003-2013) daily SM and P data from 14 measurement stations in Illinois. Correlations above 5% level of the significance were obtained during the late-spring to late-summer period, peaking at r² = 0.8 at top 50-cm SM and 21-days accumulated subsequent P. The high positive correlation corresponds to the timing of soil drying in early summer. Contrary to the previous study, there is greater correlation between SM and future P at deeper soil layers than that at the surface layers, which is indicative of the influence of SM memory in the future P. Comparisons of the correlations between the antecedent P to SM and the autocorrelation of P itself show that, while the prior P significantly forces surface SM, its influence decreases at deeper layers where the influence of SM to future P increases. This main findings of this research are (1) the important role of deep soil layers in influencing future precipitation, and (2) the timing of the onset of soil drying in exerting the influences on future P.