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GASS- WTG project

Participants: Chimene Daleu1 ,Steve Woolnough 1, Bob Plant1, Adam Sobel2, Shunguang Wang2, Sharon Sessions3, Dave Raymond3, Gilles Bellon4, Chris Bretherton5 , Zhiming Kuang6

1University of Reading, 2Columbia University, 3New Mexico Tech, 4 Centre national de recherches météorologiques,5 University of Washington, 6 Harvard School of Engineering and Applied Sciences

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Parameterized large-scale dynamics is a set of methods developed in the past decade for studying the interactions between tropical deep convection and large-scale dynamics in limited area models. These methods have been developed based on our physical understanding of tropical atmosphere and their principle advantage is that they offer a pathway to attack the key question of what controls large-scale variation of tropical deep convection. In the past, these methods have been used in both single column models (SCMs) and cloud-resolving models (CRMs) to study a range of problems in which two-way interactions between deep convection and the large-scale play a central role. While much insight has been learned from these efforts, many aspects of these methods remain uncertain since both agreement and discrepancies are seen in the various published results. It is unclear to what extent various aspects of their formulation are responsible for the agreements and discrepancies seen in the published results, and how robust these results are.

In this context, the Working Group on Parameterized large-scale dynamics has proposed the GASS-WTG project at the Pan-GASS meeting in September 2012. The acronym WTG refers to the Weak Temperature Gradient approximation, which is one method to parameterize large-scale dynamics; it is used here for historical reasons, but we are not limited to the WTG method per se - another method, the Damped-gravity-wave (DGW), will also be explored extensively in this project. The goal of the GASS-WTG project is to develop community understanding of different aspects of the parameterization methods currently in use. i.e, their strengths, weaknesses, and functionality in models with different physics and numerics.

Model specifications and experimental setup can be found here

Submission Deadlines

The deadline for submitting data for this intercomparison project is 1 May 2014.


Models should be modified to implement the WTG/DGW calculations using the following subroutines.

Change log

All important changes will be tracked here:

Submitting Results

Participants should refer to section 5 of the proposal, which gives information on:

Participants should gzip the file and make them available via anonymous ftp on a web page and e-mail instructions on how to retreive them directly to


The first draft that summarizes the first results from this project can be downloaded here.

Comments should be sent to