Soil moisture anomalies and convection: investigation using ground-based measurements at US Southern Great Plains

Abstract:

Soil moisture is one of the key factors modulating the atmospheric boundary layer and thus the climate system. In this study, we use ground-based measurements to investigate the mechanism by which soil moisture anomalies affect clouds and precipitation. From decade-long warm season observation by Department of Energy Atmospheric Radiation Measurement at Southern Great Plains, we carefully select daytime weather regimes that are strongly coupled with land-surface processes such as clear-sky dry convection days, forced and active non-precipitating shallow cumuli days, and late-afternoon deep convective raining days (Zhang and Klein, 2010 and 2013). Based on this framework, we statistically assess: 1) the differences in soil moisture and surface heterogeneity between different convective regimes; and 2) the variances of the associated effects on surface and boundary layer meteorological conditions inside each convective regime. A specific question will be: under different soil moisture conditions, e.g. wet/dry, which convective weather regime will be favored and how this is related to large-scale environmental factors, such as free-troposphere stability and humidity? The answer to this question will improve our understanding of how soil moisture impacts boundary layer turbulence and thermodynamics, and influences the convection triggering and maintenance and their feedbacks on soil moisture, thus establish a link between soil moisture and convection at the process level.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675737