Variability of Successive Cold Pools in BACS-I

Cold pools, or evaporatively cooled outflows from convective storms, can transport aerosols and impact weather and climate. For instance, cold pools can loft and transport dust which affects Earth’s radiative budget. Cold pools can also initiate convective storms and alter their lifetime, intensity, and organization. Previous studies have shown how cold pool characteristics vary by environment, land surface, and properties of their parent storms. However, the variation of cold pool properties and propagation speeds that pass through the same region on the same day has seldom been studied. Thus, the goal of this study is to examine the variability of characteristics and processes of successive cold pools that occur on the same day within similar environments.

Phase I of the BioAerosol and Convective Storms (BACS-I) campaign was conducted at the Central Plains Experimental Range (CPER) in Northern Colorado in May-June 2022. During BACS-I, of the 23 cold pools observed, 13 occurred after a cold pool had previously passed through the fixed observation site on the same day. This study utilizes thermodynamic and dynamic data gathered by radiosondes, a surface station, and uncrewed aircraft systems (UAS) to determine the variability of cold pool characteristics between successive cold pools that passed CPER on the same day. Furthermore, to examine the processes driving the observed differences in these subsequent cold pools, two idealized successive line cold pools, motivated by a multi squall line cold pool case observed during BACS-I, have been simulated using the Regional Atmospheric Modeling System (RAMS) model. Results from the simulations show that the first cold pool passage creates a stratified stable layer that decreases wind speeds near the surface compared to the pre cold pool environment. This increases the wind shear ahead of the second cold pool, which has a deeper leading edge compared to the first cold pool. Analysis of the variability of the characteristics of successive cold pools observed during BACS-I, as well as the mechanisms driving their differences, will be presented.