Near-surface Atmospheric Variability in Pre- and Post-convective Environments as Observed by Small Uncrewed Aerial Systems

Small uncrewed aerial systems (sUASs) are becoming increasingly popular observing platforms for atmospheric research due to their relatively low costs, their portability, and their flight flexibility. In particular, multi-rotor sUASs have gained much attention due to their ability to hover over a stationary location and their ability to take-off and land vertically from various locations. Previous sUAS profiling studies have focused on using sUASs to obtain high vertical resolution measurements to monitor the general variability of the planetary boundary layer to advance weather forecasting and enhance knowledge of atmospheric processes. However, no previous literature has used sUASs to characterize the near-surface vertical profile variability within pre- and post-convective environments, including inside convective cold pools, which have been shown to enhance the environmental spatial variability at the surface. The objective of this study is thus to evaluate the spatiotemporal variability of near-surface atmospheric profiles observed by sUASs in pre-convective, cold pool, and post cold pool environments.

The BioAerosol and Convective Storms (BACS) field campaign was conducted in May-June of 2022 and 2023 at the Central Plains Experimental Range in Nunn, Colorado. As part of the suite of instruments to measure atmospheric conditions in quiescent, pre-convective, cold pool, and post cold pool environments, four multi-rotor sUASs were utilized. The sUASs flew for multiple ~15 minute intervals during times of interest. Three of the sUASs hovered during flights at 120, 235, and 350 m AGL. The fourth sUAS flew vertical profiles from ~5 m to 350 m AGL at a constant speed of ~3 m/s. Each sUAS was equipped with a 3-D printed structure called a chimney, which housed an iMET XQ-2 sensor containing pressure, temperature, and relative humidity sensors. On the hovering sUASs, the chimney also housed Alphasense OPC N3 optical particle counters to measure aerosol counts from 0.5 to 40 micron. In addition to the measurements made on sUASs, radiosondes were also launched alongside the sUAS flights. In this presentation, temperature and humidity profiles made by the profiling sUAS will first be compared with radiosonde profiles and hovering sUAS measurements to assess the validity of sUAS profile thermodynamic measurements made with the chimney. Preliminary results suggest that the descending portions of the profile have a warm bias compared to the ascending portions of the profiles, possibly due to drone induced warming. Then, the temporal variability of thermodynamic and aerosol profiles before, during, and after cold pool passage will be examined. Initial results suggest that the spatiotemporal variability of near-surface temperature and humidity profiles is greatest inside cold pools and low-level (near 100m AGL) layers of enhanced submicron aerosol number concentrations were commonly observed inside cold pools. Mechanisms driving the observed changes of profiles inside cold pools compared to the pre-cold pool profiles will be discussed. Finally, a comparison between near-surface vertical thermodynamic and aerosol profiles in different convective regimes will be presented.