The northern hemisphere tropospheric response to changes in the gravity‐wave drag scheme in a perpetual January GCM

• Published in: Quarterly Journal of the Royal Meteorological Society
• Main Author: Stephenson, David B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1994
• Subjects: Arctic
• Online Access: http://dx.doi.org/10.1002/qj.49712051709; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fqj.49712051709; https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.49712051709

Abstract The sensitivity of a general‐circulation‐model climatology to changes in the gravity‐wave drag scheme is investigated with particular emphasis being placed upon the northern hemisphere wintertime tropospheric circulation. It is found that by weakening the upper‐level drag, the Ferrel‐cell circulation intensifies to the north, resulting in a greater than 10 K cooling in the region of the arctic tropopause. The poleward side of the northern hemisphere sub‐tropical jet intensifies in the region of 60–70°N, and a poleward shift is observed in the eddy meridional momentum flux. A large part of the response is zonally asymmetric, with the Aleutian and Icelandic lows becoming shallower with weakened upper‐level gravity‐wave drag. By comparing the results of a gravity‐wave drag scheme having a wave‐breaking vertical profile with those of a simple uniform drag‐profile scheme it appears that the tropospheric response to weakened upper‐level drag depends very little upon the choice of vertical drag profile in the troposphere.