An investigation of hydrometeor latent cooling upon convective cold pool formation, sustainment, and properties

Downdrafts extending from convective clouds can produce cold pools that propagate outward, sometimesinitiating new convection along their leading edges. Models operating at scales requiring convective parameterizations usually lack representation of this detail, and thus fail to predict this convective regenerationand longer episodes of convective activity. Developing such parameterizations requires an improved understanding of the physical drivers of cold pools, and detailed studies of the roles of all the contributingmicrophysical processes have been lacking. This study utilizes a set of 12 simulations conducted within a singleconvective environment, but with variability in the microphysical fields produced by varying parametersinfluencing warm-rain or ice processes. Time-integrated microphysical budgets quantify the contribution ofeach hydrometeor type to the total latent cooling occurring in the downdrafts that form and sustain the coldpool. The timing of the onset of the cold pool is earlier in cases with a stronger warm rain process, but bothgraupel and rain were equally as likely to be the dominant hydrometeor in the downdraft first forming the coldpool. Graupel sublimation is the dominant term in sustaining the cold pool in all simulations, but the evaporation of rain has the strongest correlation to the cold pool expansion rate, depth, and intensity. Reconcilingthe current results with past studies elucidates the importance of considering: graupel sublimation, the latentcooling only in downdrafts contributing to the cold pool, and latent cooling in those downdrafts at altitudesthat may be significantly higher than the melting level.