Dependence of Convective Cell Properties on Meteorological and Aerosol Conditions during TRACER

Precipitation from deep, moist convection plays a vital role in Earth's energy balance and water cycle. Often characterized by strong updrafts, rapid hydrometeor particle growth, and frequent lightning, convective cells present significant challenges for accurate representation in numerical models. To gain a deeper understanding of cloud-aerosol interactions in deep convective systems, the Tracking Aerosol Convection Interactions Experiment (TRACER) was conducted in and near the Houston, TX, area during 2021-2022. The evolution of numerous convective cells under various environmental conditions was tracked using the second generation of the C-Band Scanning ARM Precipitation Radar (CSAPR2) and other collocated instruments. This study investigates the properties of convective cells observed during the TRACER Intensive Operational Period (IOP) from June to September 2022 using a convective cell tracking dataset. This dataset includes rapid scan observations of individual convective cells to capture the evolution of their microphysical and dynamical characteristics during TRACER. Over 400 deep convective cells were analyzed and classified into three categories: purely isolated cells, splitting cells (initially isolated but eventually splitting into two or more cells), and clustering cells (those within a cluster). The spatial distribution indicated a widespread occurrence of convective cells across the study region, encompassing a range of meteorological and aerosol conditions. The complete lifetimes of the convective cells were obtained from the nearby KHGX radar (an operational WSR-88D radar), which provided broader spatial and temporal coverage. Results show that the lifetimes of purely isolated cells ranged from 20 to 90 minutes; more than ~50% cells have a lifetime of 30-60 minutes. Splitting and clustering cells have lifetimes ranging from 30 to 120 minutes and from 25 to 120 minutes respectively. Peak occurrences for splitting cells are observed at 40-80 minutes, accounting for approximately 50% of cases, while clustering cells show a dominant occurrence rate of over 15% across all time bins from 30 to 90 minutes. Cells are further classified into three lifetime categories: short-lived (< 40 minutes), intermediate (40-80 minutes), and long-lived (> 80 minutes). Examination of convective cell properties reveals that deeper and wider cells are associated with longer lifetimes compared to shallower and narrower cells. For short-lived cells, ~65% have depths between 5 and 7.5 km and widths less than 10 km, whereas intermediate and long-lived cells exhibit a wider range of both depth and width, with depths ranging from 5 to 15 km and widths ranging from 1 to 30 km. A significant difference in the vertical distribution of reflectivity between long-lived and short-lived cells is observed above 2 km. Long-lived cells exhibit larger reflectivities at higher altitudes, with the mean reflectivity at 4-6 km height ranging from 35-45 dBZ for ~50% of these cells, compared to 25-35 dBZ for around 50% of short-lived cells. Further, meteorological parameters associated with each cell are calculated and used to train a random forest model with cross-validation to assess the relative importance of these parameters in predicting cell lifetimes. Preliminary results indicate that the most important meteorological parameters for predicting cell lifetimes are low-level wind shear and precipitable water vapor (PWV). The dependence of convective cell properties on aerosol conditions is also examined. This study provides a deeper understanding of how environmental conditions influence convective cell properties.