Abstract
Land-atmosphere interactions play an important role in summer rainfall in the central United States, where mesoscale convective systems (MCSs) contribute to 30 to 70% of warm-season precipitation. Previous studies of soil moisture-precipitation feedbacks focused on the total precipitation, confounding the distinct roles of rainfall from different convective storm types. Here, we investigate the soil moisture-precipitation feedbacks associated with MCS and non-MCS rainfall and their surface hydrological footprints using a unique combination of these rainfall events in observations and land surface simulations with numerical tracers to quantify soil moisture sourced from MCS and non-MCS rainfall. We find that early warm-season (April to June) MCS rainfall, which is characterized by higher intensity and larger area per storm, produces coherent mesoscale spatial heterogeneity in soil moisture that is important for initiating summer (July) afternoon rainfall dominated by non-MCS events. On the other hand, soil moisture sourced from both early warm-season MCS and non-MCS rainfall contributes to lower-level atmospheric moistening favorable for upscale growth of MCSs at night. However, soil moisture sourced from MCS rainfall contributes to July MCS rainfall with a longer lead time because with higher intensity, MCS rainfall percolates into deeper soil that has a longer memory. Therefore, early warm-season MCS rainfall dominates soil moisture-precipitation feedback. This motivates future studies to examine the contribution of early warm-season MCS rainfall and associated soil moisture anomalies to predictability of summer rainfall in the major agricultural region of the central United States and other continental regions frequented by MCSs.
Highlights
Land–atmosphere interactions play an important role in summer rainfall in the central United States, where mesoscale convective systems (MCSs) contribute to 30 to 70% of warm-season precipitation
We investigate the interactions between soil moisture and rainfall in the central United States from the unique perspective of how early warm-season (April to June) MCS and non-MCS rainfall affects July MCS and non-MCS rainfall through the distinct footprints of the two rainfall components on soil moisture
Besides differences in rain intensity and area, MCS and non-MCS rainfall differ in their diurnal timing and the remote (Rocky Mountain Foothills) versus local convective triggering, all of which play important roles in how MCS and non-MCS rainfall influence soil moisture–precipitation feedback
Summary
Land–atmosphere interactions play an important role in summer rainfall in the central United States, where mesoscale convective systems (MCSs) contribute to 30 to 70% of warm-season precipitation. Early warmseason MCS rainfall dominates soil moisture–precipitation feedback This motivates future studies to examine the contribution of early warm-season MCS rainfall and associated soil moisture anomalies to predictability of summer rainfall in the major agricultural region of the central United States and other continental regions frequented by MCSs. subsequent PBL development and convection [14,15,16,17]. While the latter mechanism tends to homogenize the spatial variability of soil moisture by inducing rainfall over dry soils, the former pathway can result in persistent wet/dry soil moisture states important at larger spatial scales and longer timescales [9, 10] These contrasting modulations of the spatiotemporal variability of soil moisture by precipitation can affect subsequent rainfall differently through land–atmosphere interactions. Located in a transitional zone between the arid, western United States and the humid, eastern United States, the central United States is a hotspot of coupling between soil moisture and precipitation in summer when evapotranspiration (ET) responds strongly to soil water availability and affects
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