Studies of stratopause structure, evolution and transport from satellite data and new assimilation products

Global daily temperature datasets extending through the

mesosphere from the Sounding of the Atmosphere using

Broadband Emission Radiometry (SABER) instrument launched in

2001 and the Aura Microwave Limb Sounder (MLS) launched in

2004 are the first to allow comprehensive evaluation of the

performance of models and data assimilation systems in the

upper stratosphere through the lower mesosphere. Recent

work with these data sets has shown that operational

analyses from European Center for Medium-Range Weather

Forecasting (ECMWF) and NASA's Global Modelling and

Assimilation Office (GMAO) show serious deficiencies in

reproducing extreme events such as the prolonged

stratospheric sudden warming in the 2005-2006 Arctic winter,

and show substantial biases in global stratopause structure

and evolution under more typical conditions. New research

assimilation products show promise in improving the

representation of the stratopause with higher model tops,

more sophisticated gravity-wave drag parameterizations,

and/or assimilation of MLS and SABER data. We show

improvements in stratopause structure in analyses that

assimilate MLS data into the GMAO assimilation system. The

interannual and interhemispheric variability of stratopause

evolution and its representation in data assimilation

systems is explored, focusing on recent assimilation

products from the Canadian Middle Atmosphere Model Data

Assimilation System (CMAM-DAS) and from Naval Research

Laboratory (NRL) NOGAPS-ALPHA runs assimilating MLS and

SABER temperatures.

(Work at JPL/CalTech is done under contract with the National Aeronautics and Space Administration.)