Predictability of the 2012 Great Arctic Cyclone on medium-range timescales

• Published in: Polar Science
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2018
• Subjects: Arctic cyclone; Medium-range ensemble forecast; Predictability; Warm core; Cyclone merging; Arctic; Polar Science
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=14982; http://id.nii.ac.jp/1291/00014901/

Arctic Cyclones (ACs) can have a significant impact on the Arctic region. Therefore, the accurate prediction of ACs is important in anticipating their associated environmental and societal costs. This study investigates the predictability of the 2012 Great Arctic Cyclone (AC12) that exhibited a minimum central pressure of 964 hPa on 6 August 2012, using five medium-range ensemble forecasts. We show that the development and position of AC12 were better predicted in forecasts initialized on and after 4 August 2012. In addition, the position of AC12 was more predictable than its development. A comparison of ensemble members, classified by the error in predictability of the development and position of AC12, revealed that an accurate prediction of upper-level fields, particularly temperature, was important for the prediction of this event. The predicted position of AC12 was influenced mainly by the prediction of the polar vortex, whereas the predicted development of AC12 was dependent primarily on the prediction of the merging of upper-level warm cores. Consequently, an accurate prediction of the polar vortex position and the development of the warm core through merging resulted in better prediction of AC12. 北極低気圧（AC）は北極域の環境に大きな影響を与えるため、その正確な予測は重要である。本研究では、現業中期アンサンブル予報を用いて2012年8月6日に最小中心気圧964 hPaを記録したAC（AC12）の予測可能性を調べた。その結果、AC12の発達と中心位置を正確に予測できるようになるのは8月4日を初期日とする予報からであった。また、中心気圧と位置の誤差で分類したアンサンブルメンバー間の比較より、上層の極渦の予測がAC12の位置の予測に、低気圧の併合およびそれに伴う上層の暖気核の発達がAC12の発達の予測に影響を与えることがわかった。したがって、上層の極渦の位置と低気圧の併合による上層の暖気核の発達の両方の正確な予測が、AC12の正確な予測につながることが示された。