A climatology of polar winter stratopause warmings and associated planetary wave breaking. Issue 10 (28th May 2013)

• Record Type: Journal Article
• Authors: Greer, K.; Thayer, J. P.; Harvey, V. L.
• Is Part Of: Journal of geophysical research. Volume 118:Issue 10(2013:Oct.)
• Page Start: 4168
• Page End: 4180
• Publication Date: 2013-05-28
• Subjects: Sudden Stratospheric Warming -- Middle atmosphere dynamics -- polar winter aeronomy -- MetO -- UKMO; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/jgrd.50289
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: [1] This work presents a climatology of synoptic‐scale disturbances in the upper stratosphere lower mesosphere (USLM) based on 20.5 years of assimilated data analyses from the U. K. Meteorological Office (1991–2012). USLM disturbance criteria are established, based on stratopause warmings at the 2 hPa level, to create climatologies in both hemispheres that delineate their timing, frequency, and geographic location. USLM disturbances occur on average 2.3 times per winter in the Northern Hemisphere (NH) (November through March) and 1.6 times per winter in the Southern Hemisphere (SH) (May through September), persist on average for 8 days in the NH and only 4 days in the SH, occur most frequently in December (July) in the Northern (Southern) Hemisphere, and are predominantly located in the longitude sector between 0 o E and 90 o E in both hemispheres. This is the first work to show that all major Sudden Stratospheric Warmings (SSWs) over the 20.5 year data record are preceded by USLM disturbances. One third of USLM disturbances evolve into a major SSW; only 22% of minor SSWs evolve into a major SSW. USLM disturbances and minor SSWs illustrate, at times, similar occurrence statistics, but the minor warming criteria seem to include a more diverse range of dynamical conditions. USLM disturbances are more specific in their dynamical construct with strong baroclinicity being a necessary condition. Potential vorticity analysis indicates that all USLM events occur with planetary wave breaking and that subsequent baroclinic instability may lead to the development of USLM disturbances. Key Points: 20.5 year MetO climatology of middle atmospheric disturbances Baroclinic instability associated with PWB in the upper stratosphere Relationships between Stratopause warmings, PW activity, and SSWs