ATM S 521 Seminar: Dr. Andrew Gettelman (National Center for Atmospheric Research) "An Integrated View of the Extra-tropical Upper Troposphere and Lower Stratosphere"

Start Date/Time: Thursday, December 09, 2010, 3:30 PM
Ending Date/Time: Thursday, December 09, 2010, 4:20 AM
Location: JHN 175

-The Extra-tropical Upper Troposphere and Lower Stratosphere (Ex-UTLS) is an extended transition region between the stratosphere and the troposphere. The Ex-UTLS includes the tropopause, a strong static stability gradient and dynamic barrier to transport, which is reflected in tracer profiles. The Ex-UTLS exhibits complex dynamical, radiative and chemical characteristics that place unique requirements on observing and modeling systems. The Ex-UTLS couples the stratosphere to the troposphere through chemical constituent transport (of e.g. ozone), by dynamically linking the stratospheric circulation with tropospheric wave patterns, and via radiative process tied to optically thick clouds and clear sky gradients of radiatively active gases. A comprehensive picture of the Ex-UTLS is presented that brings together different definitions of the tropopause, focusing on observed dynamical and chemical structure, and their coupling. This integral view recognizes that thermal gradients and dynamic barriers are necessarily linked, that transport barriers give rise to the trace gas distribution, and that there are radiative feedbacks that help maintain this structure. The impacts of 21st century anthropogenic changes to the atmosphere due to ozone recovery and climate change will be felt in the Ex-UTLS, and recent simulations of these effects are summarized and placed in context. Key uncertainties and research areas are discussed.