Soil moistureprecipitation coupling: observations from the Oklahoma Mesonet and underlying physical mechanisms
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Abstract. Interactions between soil moisture and the atmosphere are driven by the partitioning of sensible and latent heating, through which, soil moisture has been connected to atmospheric modification that could potentially lead to initiation of convective precipitation. The majority of previous studies linking the land surface to subsequent precipitation have used atmospheric reanalysis or model datasets. In this study, we link in situ observations of soil moisture from more than 100 stations in Oklahoma to subsequent unorganized afternoon convective precipitation. We use hourly, high resolution NEXRAD radar-derived precipitation to identify convective events, and then compare the location of precipitation initiation to underlying soil moisture anomalies the morning prior. Overall we find a statistically significant preference for convective precipitation initiation over drier than normal soils, with over 70% of events initiating over soil moisture below the long-term median. The significant preference for precipitation initiation over drier than normal soils is in contrast with previous studies using satellite-based precipitation products to identify the region of maximum precipitation accumulation. We sub-sample 19 convective events occurring near Lamont, Oklahoma, where soundings of the atmospheric profile at 06:00 and 12:00 LST are also available. For these events, soil moisture is strongly, negatively correlated with the level of free convection, planetary boundary layer height, and surface temperature changes from 06:00 to 12:00 LST. We also find strong, positive correlations between morning soil moisture and morning-to-afternoon changes in convective available potential energy and convective inhibition. In general, the results of this study demonstrate that both positive and negative soil moisture feedbacks to the atmosphere are relevant in this region of the United States.
