A Climatology of the Stratopause in the Polar Vortices and Anticyclones: Observations and Global Modeling

France, Jeffrey Allen

Graduate Thesis Or Dissertation

A Climatology of the Stratopause in the Polar Vortices and Anticyclones: Observations and Global Modeling Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/rv042t14p

Abstract

Zonal asymmetries in stratopause temperature and height are explored by considering a global climatology based on 7 years of Microwave Limb Sounder (MLS) satellite data, from 2004 to 2011. Stratopause temperature and height is interpreted in the context of the polar vortices and anticyclones defined by the Goddard Earth Observing System (GEOS) meteorological analyses. Multiyear, monthly mean geographic patterns in stratopause temperature and height are shown to depend on the location of the polar vortices and anticyclones. The regional temperature and height anomalies, which are due to vertical ageostrophic motion associated with vertically propagating baroclinic planetary waves, are climatological features. This climatology is reproduced using 40 years of output from the Whole Atmosphere Community Climate Model (WACCM). WACCM is in excellent agreement with observations, except in the Antarctic vortex where the stratopause is ~10 K warmer and ~5 km higher compared with MLS, and the area of the vortex is 45% smaller in the SH and 30% smaller in the NH compared to GEOS. WACCM diabatic heating rates support the hypothesis that ageostrophic vertical motions are responsible for producing Arctic winter temperature anomalies. A composite of 15 elevated stratopause (ES) events based on WACCM is produced and shown to be in good agreement with the 2012 ES event observed by MLS. This analysis is the first to suggest that ES events are not pole centered. Finally, temperature observations during January and February 2006 from the High Resolution Dynamics Limb Sounder (HIRDLS), MLS, and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instruments are compared to illustrate the vertical range over which version 6 HIRDLS temperatures are scientifically useful. Though HIRDLS temperatures are consistently 5-10 K lower in the mesosphere, the horizontal temperature distribution is in good spatial and temporal agreement with MLS and SABER up to ~80 km. Gravity wave momentum flux and planetary wave-1 amplitudes are derived from HIRDLS and are in agreement with previous studies. We use HIRDLS to show a ~30 K increase in stratopause temperature following enhanced gravity wave momentum flux in the lower mesosphere.

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