Polarimetric Size Sorting Signatures in the Convective Regions of Mesoscale Convective Systems in PECAN: Implications on Kinematics, Thermodynamics, and Precipitation Pathways.

An object‐based technique was utilized to identify hydrometeor size‐sorting signatures at lower levels in the convective regions of 10 mesoscale convective systems (MCSs) during the 2015 Plains Elevated Convection at Night (PECAN) field campaign. Composite statistical analysis indicates that the magnitudes of size‐sorting signatures (the separation distances between rain diameter maxima and concentration maxima) are nonlinearly correlated to the echo‐top height, rain mass beneath the melting level, and precipitation rates at higher percentiles. To explore this correlation, the weather forecasting and research model was used to simulate the 20 June 2015 MCS during PECAN. Statistical analysis of the model outputs indicates more active riming growth and quicker graupel fallout at warmer temperatures near areas with larger separation distances. While updraft intensity above the melting level was also positively correlated to separation distances, this correlation was only statistically significant within certain temperature ranges. Additional analyses reveal that the higher intense precipitation potential near signatures with large separation distances could be attributed to precipitation production from the melted graupel. Finally, spatial correspondence between graupel distribution at the melting level and rain distribution at the lowest model level illustrates the critical role of graupel sedimentation and sorting in creating size‐sorting signatures in MCSs during the PECAN field experiment. Plain Language Summary: Recent upgrades in the US radar networks to polarimetric capabilities enabled routine measurements of how the sizes and concentration of raindrops vary in weather systems. Statistical analysis of radar data and output from a numerical model shows that the spatial distributions of raindrop sizes and concentration in the low levels could be exploited to elucidate physical processes in rainy weather systems. Specifically, low‐level raindrop size‐concentration separation may provide extra information on how much latent heating is released or absorbed when water transitions between vapor, liquid, and solid phases. This new information could be important because heating aloft can affect the intensity of the weather systems and the amount of precipitation produced by weather systems. Key Points: A positive correlation exists between the magnitudes of size sorting signatures and convective depthLarger size sorting magnitudes are associated with more riming growth and quicker graupel falloutIntense convective precipitation in the PECAN MCSs seems to be dominated more by cold rain processes than warm rain processes [ABSTRACT FROM AUTHOR]