FY 2024

Dry air outbreak and significant surface turbulent heat loss during Hurricane Ian: Satellite and Saildrone observations

Yu, L., Y. Chen, A.O. Gonzalez, C. Zhang, and G.R. Foltz

Geophys. Res. Lett., 50(23), e2023GL105583, doi: 10.1029/2023GL105583, View open access article online at Wiley/AGU (2023)

This study investigates an exceptional Gulf of Mexico dry air outbreak triggered by Hurricane Ian and fueled by dry air originating from drought-stricken mid-latitudes under a high-pressure system. The convergence of meteorological forces, combining cooler, dry air with a warmer, humid sea surface and strong winds, intensified latent and sensible heat exchanges, resulting in significant oceanic heat loss. Data from the 2022 Atlantic hurricane Saildrone mission and satellite flux analysis revealed that the outbreak's total turbulent heat fluxes peaked above 850 Wm⁻², comparable to or even surpassing the hurricane’s impact. Argo float measurements recorded a 40-m deepening of the mixed layer and a 1.4°C temperature decrease. In the tropical Atlantic, wind effects outweighed humidity in driving flux variability. Saildrone’s high-frequency linewise measurements, distinct from satellite’s footprint averages, provide unique insights into wind variability under high wind conditions.

Plain Language Summary. Dry air outbreaks in the Gulf of Mexico are meteorological events marked by the influx of drier and often cooler air masses into the typically warm and humid Gulf region. These events occur mostly during the fall and winter months and are associated with atmospheric circulation patterns, particularly the transit of high-pressure systems from the North American continent. This study highlights an exceptional dry air outbreak in late September 2022, triggered by Hurricane Ian and intensified by dry air originating from drought-stricken mid-latitudes, a condition sustained by a persistent high-pressure system. The interaction between cold, dry air and warm, humid sea surface, coupled with strong winds, intensified the turbulent transfer of heat from the ocean to the atmosphere, resulting in significant ocean heat loss. Data from the 2022 Atlantic hurricane Saildrone mission and satellite flux analysis revealed that the outbreak’s total turbulent heat fluxes peaked above 850 Wm⁻², comparable to or even surpassing the hurricane’s impact. Concurrently, the ocean’s surface layer deepened by about 40 m, and the temperature dropped by around 1.4°C. These findings hold substantial implications for understanding the Gulf's weather patterns and their impact on tropical storms, with the potential to influence both their intensity and trajectories.