CHELAX-BNF

Characterizing HEterogeneous Land-Atmosphere eXchanges at BNF

1 June 2025 - 30 June 2025

Lead Scientist: Timothy Juliano

Observatory: AAF (ARM Aerial Facility) - BNF

Shallow convection over the southeastern United States (SEUS) plays a critical role in the region’s weather and ecosystem, yet its connection with land-atmosphere exchanges remains poorly understood. The SEUS is characterized by heterogeneous landscapes, where variations in land cover, soil moisture, and surface roughness influence the development of the atmospheric boundary layer (ABL) and the development of moist convection. While prior research has highlighted the importance of land surface heterogeneities in modulating convective processes, weather and Earth system models continue to struggle with representing these small-scale variations. To address these gaps, the Characterizing HEterogeneous Land-Atmosphere eXchanges at BNF (CHELAX-BNF) experiment will leverage a combination of surface-based and airborne observations to investigate how spatial variations in land surface properties influence ABL evolution, coherent turbulent structures, and aerosol transport in a region where locally forced shallow convection frequently develops.

CHELAX-BNF will take place at the ARM Bankhead National Forest (BNF) Facility and its surroundings, using the U.S. Department of Energy (DOE) ARM ArcticShark uncrewed aerial system (UAS) alongside existing surface instrumentation to provide a comprehensive data set on land-atmosphere interactions. The campaign will employ multiple flight strategies to capture different aspects of ABL processes. A high-altitude mapping flight will characterize surface heterogeneity, providing insight into land use gradients that influence local circulations. A series of flux legs and vertical profiles will be conducted to examine spatial variability in ABL turbulence, the evolution of coherent structures, and the connection between surface conditions and aerosol distributions. Additionally, low-altitude box flights will focus on resolving near-surface exchanges and ABL development during the morning transition period. These observations will help quantify not only the coupling between land use variability and microscale/mesoscale atmospheric motions in shaping convective environments near the BNF site, but also the representativeness of the BNF supplemental sites relative to the main site. By providing much-needed data to enhance our fundamental understanding of complex land-atmosphere interactions, we aim to also inform thoughtful numerical modeling experiments that will shed light on model deficiencies.

This work directly supports the mission of the DOE Earth and Environmental System Sciences Division by improving fundamental understanding of land-atmosphere exchanges, a key component of the Earth’s hydrological and energy cycles. By integrating advanced airborne measurements with ground-based observations, CHELAX-BNF will provide novel insights into how land surface heterogeneity influences atmospheric processes at scales unresolved or under-resolved by current models. We expect these findings will contribute to an improved representation of shallow convection in numerical weather and Earth system models through parameterization development, aligning with DOE’s broader goal of enhancing predictive capabilities for atmospheric and environmental processes.