Real-time forecasts over the Arctic region during 2017/2018 Arctic expedition of the KOPRI IBRV Araon

Abstract

The Korea Polar Research Institute (KOPRI) has an ice-breaking research vessel (IBRV) Araon, and radiosonde observations have been taken during the Arctic cruise period of the Araon since 2015. Starting in 2017, the KOPRI performs real-time weather forecasts over the Arctic region during the Araon’s Arctic cruise period (August 6 to September 16 in 2017, August 4 to September 20 in 2018) to support scientific activities of the Araon. 6-hourly radiosonde observations from the Araon are assimilated using the three-dimensional variational (3D-Var) data assimilation method in a cycling mode, and 5-day forecasts are made using the polar-optimized Weather Research and Forecasting (Polar WRF) Model on every Monday, Wednesday, and Friday. Forecasts results such as sea-level pressure, 2-m temperature, 2-m relative humidity, 10-m wind speed/direction, and precipitation are transmitted to the Araon. Effects of assimilating radiosonde observations from the Araon on weather forecasts over the Arctic region are investigated by comparing two experiments: one with the assimilation of radiosonde observations and the other without the assimilation of radiosonde observations. Verification statistics against reanalysis data (e.g., ERA-Interim from the European Centre for Medium-range Weather Forecasts) and independent observations (e.g., buoy observations from the International Arctic Buoy Programme) are calculated for the Arctic cruise periods in 2017 and 2018. Some cyclone cases over the Arctic region are also analyzed to show impacts of assimilating radiosonde observations on 5-day forecasts of those cyclones.