Summertime Marine Fog Variability in King George Island, Antarctic Peninsula, Using Special Upper-Air Observations and Cloud-Resolving Simulations

Abstract In this study, the occurrence of austral summer marine fog events at King George Island, off the Antarctic Peninsula, was investigated using surface observations, special upper-air soundings, reanalysis data, and cloud-resolving simulations with the Weather Research and Forecasting (WRF) Model. The study describes the seasonal and diurnal patterns of low-visibility conditions associated with fog (Fg) and mist (Br) events on King George Island. It shows that Fg and Br are each present 15%–20% of the time during the warm season (October–March) and are less common from June to August. The high frequency of fog during warmer months aligns with findings from previous research, indicating a regional marine fog hotspot in the Antarctic Peninsula region that extends beyond the island itself and more frequently originating offshore. Most Fg and Br events happen during northwesterly windy days bringing warmer and humid air, with calm-wind-related fog being rare. Additionally, the small diurnal variability of these events implies that they are influenced by broader atmospheric patterns and ocean fluxes rather than just daily temperature shifts. Observations were gathered during two Colombian Antarctic Program research campaigns, designed to observe the vertical and temporal variability of the atmosphere during these visibility conditions, as well as their synoptic drivers. The field campaigns were carried out between 20 January and 24 January 2020, and between 14 February and 6 March 2022. During our field campaigns, sea fog episodes were present in 10 out of 24 days. Northwesterly low-level flow prevails during foggy days, as extratropical short-wave low pressure systems propagated over the Drake Passage. The warm quadrant of the cyclonic system promoted warm air advection over colder seawaters, leading to fog formation. Regional climate modeling simulations using WRF add value and help confirm the advective nature of the fog episodes, with the model capturing the fog day-to-day variability and overall vertical structure characteristics. This study presents our field campaign observations and analysis during fog episodes, while presenting encouraging explicit simulations of marine fog characteristics, suggesting a strong potential for numerical weather predictions of fog for the region.