Joint Seminar: EMAC-CLaMS: A Climate Model with Lagrangian Tracer Transport in the Stratosphere

Modern climate models have a number of robust stratospheric features, some of which are not robust within observations or explicitly conflict with them. Most notable among these are Brewer-Dobson circulation trends, which show a robust and global acceleration within climate models but have a more complicated form in observation-based inferences (although few of these exist). Also notable is the model wet bias, wherein climate models show approximately double the amount of stratospheric water vapor as is observed, in some regions.

Previous work has shown that model transport schemes could contribute to the stratospheric wet bias, raising suspicion that other model features - particularly in the stratosphere - could have baises caused by the model transport scheme.
The EMAC-CLaMS project aims to understand this possible influence through development and analysis of a climate model with a Lagrangian transport scheme applied to tracers transport in the stratosphere and upper troposphere. Precisely, the Chemical Lagrangian Model of the Stratosphere (CLaMS) - a Lagrangian chemical transport model - is coupled into EMAC (the MESSy version of ECHAM). This coupling allows EMAC to drive advection within CLaMS, and allows CLaMS to control the gradients of radiation-relevant chemicals in EMAC, such that EMAC-CLaMS is a climate mode with Lagrangian tracer transport.

Because the radiative feedback from CLaMS onto EMAC will cause changes in the EMAC winds, a desirable first step to understanding the model involves characterizing the differences between EMAC and CLaMS transport in the absence of a radiative feedback. The first results of this step using the age spectrum method (a series of passive tracers pulsed at different times, describing a distribution of the age of air) will be presented, in addition to an overview of the  EMAC-CLaMS project.




13:30 h


Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg


Edward Charlesworth, Forschungszentrum J├╝lich


Sally Dacie

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