Fig 4.

Intraseasonal oscillations in a GCM: composite 500-mb maps from the perpetual-January GCM experiment of Marcus et al. (70). (a) For days on which the 36–60 day NH extratropical AAM exceeded 1.5 times its rms value; maps for days with a negative (positive) anomaly were added with a positive (negative) sign. (b) Constructed from maps taken 12 days earlier than those included in a. Contour interval is 20 m, and negative contours are dashed. [Reproduced with permission from ref. 70 (Copyright 1996, American Meteorological Society).]