Intensified Cold Pool Dynamics Under Stronger Surface Heating

Abstract

AbstractThe observed increase of convective extreme precipitation intensities with temperature beyond the Clausius‐Clapeyron rate has recently directed attention to nonequilibrium processes that might cause the increase. While out‐of‐equilibrium simulations with perturbed heating conditions show clear increases in convective precipitation intensities, it has so far remained unclear, to which extent precipitation intensities can increase, when the atmosphere is in “perpetual equilibrium” (PE). We use the term PE to describe periodically forced diurnal cycles that eventually yield an approximately repetitive atmospheric response from day to day. In PE, as defined here, precipitation extremes increase at rates beyond the Clausius‐Clapeyron rate. When analyzing causes for the increase, we find the variance in near‐surface temperature to increase significantly as precipitation builds up throughout the day and that this temperature variance is larger when surface heating is increased. We propose that enhanced rain evaporation may drive a feedback, by which cold pool activity, and the possible collision of cold pool gust fronts, is strengthened—thereby intensifying subsequent convective updrafts and their precipitation.