Stratospheric Flow during Two Recent Winters Simulated by a Mechanistic Model

Abstract

The authors have used a spectral, primitive equation mechanistic model of the stratosphere and mesosphere to simulate observed stratospheric flow through the winters of 1991?92 and 1994?95 by forcing the model at 100 hPa with observed geopotential height. The authors assess the model?s performance quantitatively by comparing the simulations with the United Kingdom Meteorological Office (UKMO) assimilated stratosphere?troposphere data. Time-mean, zonal-mean temperatures are generally within 5 K and winds within 5 m s?1; transient features, such as wave growth, are mostly simulated well. The phase accuracy of planetary-scale waves declines with altitude and wavenumber, and the model has difficulty correctly simulating traveling anticyclones in the upper stratosphere. The authors examine the minor warming of January 1995 which was unusual in its depth and development and which the model simulated fairly well. The authors also examine the minor warming of January 1992, which the model missed, and a major warming in February 1992 that occurred in the model but not in the observations.