Precipitation phase transition in austral summer over the Antarctic Peninsula

Abstract

Investigating precipitation phase transitions is crucial for improving our understanding of precipitation formation processes and impacts, particularly in Polar Regions. This study uses observational data and numerical modelling to investigate precipitation phase transitions in the western and northern Antarctic Peninsula (AP) during austral summer. The analysis is based on the ERA5 reanalysis product, dynamically downscaled using the Polar-WRF (Polar Weather Research and Forecasting) model, evaluated using regular meteorological observations and additional measurements made during the Year of Polar Prediction special observing period. We analyse three cases of extra-tropical cyclones bringing precipitation with phase transitions, observed at the Chilean station Professor Julio Escudero (King George Island, north of the AP) and the Ukrainian Antarctic Akademik Vernadsky station (western side of the AP) during the first week of December 2018. We use observed and modelled near-surface air temperature and pressure, precipitation amount and type, and vertical temperature profiles. Our results show that precipitation type (snow or rain) is well-represented by ERA5 and Polar-WRF, but both overestimate the total amount of precipitation. The ERA5 daily variability and vertical air temperature profile are close to the observed, while Polar-WRF underestimates temperature in the lower troposphere. However, ERA5 underestimates the temperature inversion, which is present during the atmospheric river event, while Polar-WRF represents that inversion well. The average weekly temperature, simulated with Polar-WRF, is lower compared to ERA5. The Polar-WRF fraction of snow in the total precipitation amount is higher than for ERA5; nevertheless, Polar-WRF represents the precipitation phase transition better than ERA5 during the event, associated with an atmospheric river. These case studies demonstrated a relationship between specific synoptic conditions and precipitation phase transitions at the AP, evaluated the ability of the state-of-the-art reanalysis and regional climate model to represent these events, and demonstrated the added value of combined analysis of observations from the western and northern AP, particularly for characterizing precipitation during synoptic events affecting the entire AP.

Climate projections over the Antarctic Peninsula region to the end of the 21st century. Part III: clouds and extreme precipitation

“…In our view, the conclusions of Palerme et al (2017) and our previous estimations allow us to have high confidence in our obtained results based on CORDEX RCMs driven by CMIP5, notwithstanding we analyzed only the liquid share of total precipitation. There was an increase of such liquid precipitation in the AP region in previous warm events (e. g., Chyhareva et al, 2021;Wille et al, 2022) and expected with future warming based on an ensemble of the next-generation CMIP6 models (Vignon et al, 2021).…”

“…It is shown that combining clouds with liquid precipitation could enhance melting events by hindering freezing processes (Van Tricht et al, 2016). On the other hand, phase transition of precipitation on the ground is still a big challenge for predicting and needs more focused research with simulation and measurements as were recently studied with ERA5 reanalysis product downscaled by Po lar-WRF model and additional measurements at Aka demik Vernadsky (hereinafter Vernadsky) and Escu dero stations (Chyhareva et al, 2021).…”

Measured and modeled vertical structure of precipitation during mixed-phase event near the West Coast of the Antarctic Peninsula

“…Hence, the modeling resolution should be increased. Although, Chyhareva et al (2021) showed that the Polar WRF model has good applicability in the simulation of the precipitation phase transitions for this region.…”

Strong Warming Over the Antarctic Peninsula During Combined Atmospheric River and Foehn Events: Contribution of Shortwave Radiation and Turbulence

“…Two surface melting events that were triggered by the combined impact of ARs and foehn warming are studied, occurring on the northern AP in December 2018 and February 2022. In December 2018, a high precipitation amount (up to 5.7 mm/day) was observed at Vernadsky (Chyhareva et al, 2021), and surface melting also detected on the leeside based on National Snow and Ice Data Center (NSIDC) daily surface melt extent (not shown). At the beginning of January 2022, a large expanse of sea ice (about 2,000 km 2 ), which had persisted in the Larsen B embayment since 2011 and that can bond to and stabilize the ice shelves, began to break up between 17 and 19 January 2022 (acquired by MODIS on NASA's Terra and Aqua satellites).…”