Improved forecasts of winter weather extremes over midlatitudes with extra Arctic observations. Issue 2 (1st February 2017)

• Record Type: Journal Article
• Authors: Sato, Kazutoshi; Inoue, Jun; Yamazaki, Akira; Kim, Joo‐Hong; Maturilli, Marion; Dethloff, Klaus; Hudson, Stephen R.; Granskog, Mats A.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 2(2017)
• Page Start: 775
• Page End: 787
• Publication Date: 2017-02-01
• Subjects: Arctic -- winter extremes -- weather forecast -- radiosonde; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2016JC012197
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Recent cold winter extremes over Eurasia and North America have been considered to be a consequence of a warming Arctic. More accurate weather forecasts are required to reduce human and socioeconomic damages associated with severe winters. However, the sparse observing network over the Arctic brings errors in initializing a weather prediction model, which might impact accuracy of prediction results at midlatitudes. Here we show that additional Arctic radiosonde observations from the Norwegian young sea ICE expedition (N‐ICE2015) drifting ice camps and existing land stations during winter improved forecast skill and reduced uncertainties of weather extremes at midlatitudes of the Northern Hemisphere. For two winter storms over East Asia and North America in February 2015, ensemble forecast experiments were performed with initial conditions taken from an ensemble atmospheric reanalysis in which the observation data were assimilated. The observations reduced errors in initial conditions in the upper troposphere over the Arctic region, yielding more precise prediction of the locations and strengths of upper troughs and surface synoptic disturbances. Errors and uncertainties of predicted upper troughs at midlatitudes would be brought with upper level high potential vorticity (PV) intruding southward from the observed Arctic region. This is because the PV contained a "signal" of the additional Arctic observations as it moved along an isentropic surface. This suggests that a coordinated sustainable Arctic observing network would be effective not only for regional weather services but also for reducing weather risks in locations distant from the Arctic. Key Points: Additional Arctic radiosonde observations during winter improved forecast skill of cold extremes at midlatitudes The trajectory of high potential vorticity is important for understanding the origin of the large uncertainties in the upper troposphere The uncertainty originated from the denial of extra observations over the Arctic reached midlatitude within a week