Intense precipitation events during polar winter over the Academic Vernadsky station: clouds, precipitation and temperature extremes

Abstract

West Antarctica and the Antarctic Peninsula are considered to be climate tipping point regions where climate change processes can cause irreversible impacts. The Antarctic Peninsula region has a unique ecosystem, which can be harmfully affected by these changes. In the past decades have from Pacific mid-latitudes and specifically atmospheric rivers, accompanied by mixed-phase clouds and precipitation, can lead to surface melt on both sides of the Antarctic Peninsula. This study focused on intense precipitation events during the winter in the Southern Hemisphere in 2022 in the Antarctic Peninsula observed during the Year of Polar Prediction targeted observing periods. Polar WRF (v. 4.5) simulation data with grid step 1km and temporal resolution 10 minutes were analysed for the region of Academic Vernadsky station, Antarctic Peninsula mountains and former glacier Larsen B bay. Distributions of clouds and precipitation were analysed, as well as their concentrations and phases in the cross-section of the mountains. Also, temperature profiles were examined in the cross-sections, specifically for the 2km profile. According to the simulations data, based on Thompson’s microphysical scheme found that mixed phased and liquid clouds and precipitation could occur up to 3km even in August, which is climatically the coldest month over the coastal areas and mountains. Maximum concentrations of ice crystals and liquid droplets could exceed 1g/kg. After the intense precipitation that occur on the western Antarctic Peninsula slopes, strong warming up to 6°C in a 2km layer is simulated for the eastern slopes of AP (Larsen B ice shelf embayment). Simulation results were compared with radiosounding data and instrumental measurements at the Akademic Vernadsky station. According to the radiosounding that were held during all events, Polar WRF underestimated the temperature in the lower troposphere (up to around 950hPa), which can impact the surface precipitation phase and temperature simulations. However, as far as Polar WRF simulations for wind speed, direction, temperature, and vertical movements are correlated with radiosounding data, we can assume that the distribution of considered microphysical and thermodynamical characteristics gained from Polar WRF simulations are trustable.