Global climatology of inertial instability and Rossby wave breaking in the stratosphere

Abstract

Climatologies using United Kingdom Met Office assimilated analyses from November 1991 through March 2004 are used to juxtapose the evolution of inertial instability and Rossby wave breaking in longitude, latitude, altitude, and time. The results for the upper and middle stratosphere indicate deep poleward and eastward channels of higher inertial instability frequency extending from the central equatorial Pacific in both winter hemispheres. These corridors of enhanced inertial instability frequency are generally found just poleward of regions of frequent Rossby wave breaking, a result confirmed with a case study drawn from the period of the climatology. Both of these patterns are evident from the stratopause downward into the middle stratosphere, with the frequency of events diminishing with decreasing altitude. Analysis of interannual variability of Rossby wave breaking and inertial instability in the middle stratosphere channels confirms a correlation between them, as well as a possible quasi‐biennial oscillation signal in the early years of the climatology. In the lower stratosphere a channel of enhanced inertial instability frequency exists near east Asia in Northern Hemisphere winter, again just poleward of a Rossby wave breaking maximum. These results generally agree closely in space and time with, and significantly extend, the relatively few previously published climatologies and case studies of episodes of Rossby wave‐triggered inertial instability for the stratosphere.