Evaluation of northern hemisphere blocking climatology in the global environment multiscale model

• Published in: Monthly Weather Review
• Main Authors: Dunn-Sigouin, E., Son, S.-W., Lin, H.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Meteorological Society 2023
• Subjects: ATMOSPHERIC BLOCKING; MEAN-FLOW; GEM MODEL; PART II; CIRCULATION; INDEX; PROPAGATION; FREQUENCY; ATLANTIC; PERSISTENCE; Blocking; Climatology; North Atlantic
• Online Access: https://hdl.handle.net/10371/207695; https://doi.org/10.1175/MWR-D-12-00134.1

The performance of the Global Environmental Multiscale (GEM) model, the Canadian operational numerical model, in reproducing atmospheric low-frequency variability is evaluated in the context of Northern Hemisphere blocking climatology. Thevalidation is conducted by applying a comprehensive but relatively simple blocking detection algorithm to a 20-yr (1987-2006) integration of the GEM model in climate mode. The comparison to reanalysis reveals that, although the model can reproduce Northern Hemisphere blocking climatology reasonably well, the maximum blocking frequency over the North Atlantic and estern Europe is generally underestimated and its peak season is delayed from late winter to spring. This contrasts with he blocking frequency over the North Pacific, which is generally overestimated during all seasons. These misrepresentations of blocking climatology are found to be largely associated with thebiases in climatological background flow. The modeledstationary waves show a seasonal delay in zonal wavenumber 1 and an eastward extension in zonal wavenumber-2 components consistent with blocking frequency biases. High-frequency eddies are, however, consistently underestimated both in the NorthAtlantic and Pacific, indicating that the biases in eddy fields might not be the main reason for the blocking biases in the North Pacific. © 2013 American Meteorological Society. Y 1