GASS Projects

GASS Projects are listed below with descriptions and contact information for anyone interested in learning more about a particular project.

GEWEX Atmospheric Boundary Layer Study 3 (GABLS-3)

Contacts: Bert Holtslag and Gunilla Svensson
GABLS-3 Websites:

GABLS coordinates research on boundary layer physics to improve the representation of the atmospheric boundary layer in models. The GABLS-3 large-eddy simulation (LES) intercomparison case is based on a moderately stratified, baroclinic, mid-latitude boundary layer observed over Cabauw, the Netherlands on 1 July 2006.

GEWEX Atmospheric Boundary Layer Study 4 (GABLS-4)

Contact: Eric Bazile

This GABLS case study examines the interaction of a boundary layer of strong stability with a surface possessing a low conductivity and a high cooling potential, such as snow. The case is explored using observations at the Antarctic Plateau, and the intercomparison involves land-snow surface models, single column models, and large eddy simulations.

GEWEX Process Evaluation Study on Upper Tropospheric Clouds and Convection (UTCC PROES)

Contact: Claudia Stubenrauch

The GEWEX UTCC PROES working group aims to gain a better understanding of the interconnection between the convection and the properties of the outflowing anvils. The focus will be widened to the role of cirrus originating from in situ freezing driven by large-scale forcing, via a link to the Stratosphere-troposphere Processes And their Role in Climate (SPARC) Project.

Vertical Structure and Diabatic Processes of the Madden-Julian Oscillation: A joint project with the MJO Task Force using YOTC data

Contacts: Xianan Jiang and Prince Xavier

The objective of this project is to understand the role that convection, cloud, radiative, and dynamic processes play in the development and evolution of the MJO in order to achieve better fidelity of the MJO in global prediction models.

Clouds Above the United States and Errors at the Surface (CAUSES)

Contact: Cyril Morcrette and Hsi-Yen Ma

CAUSES is a joint GASS/DOE-RGCM/DOE-ASR project that aims to use observational data from the Atmospheric Radiation Measurement (ARM) program’s Southern Great Plains (SGP) site to understand the role that clouds have in creating the surface temperature error seen over the American mid-west in a number of general circulation models.

Microphysics Project

Contact: Ben Shipway

This project aims to create a better understanding of the differences between 3-D models in different intercomparison cases.

Boundary Layer Cloud Projects

Contact: Adrian Lock

The Boundary Layer Cloud Projects will improve the physical parameterizations of clouds and cloud-related processes and their interactions.

CFMIP-GASS Intercomparison of LES and SCMs (CGILS)

Contacts: Minghua ZhangChris Bretherton, and Peter Blossey
CFMIP Website:

The objective of CGILS is to improve understanding and simulation of boundary-layer cloud feedbacks on climate through intercomparison of LES and single-column models forced by idealized climate perturbations.

Polar Cloud Project

Contacts: Mikhail Ovchinnikov and Hugh Morrison

The Polar Cloud Project seeks to understand the role of dynamical and microphysical processes and their interactions in mixed-phase Arctic clouds.

Cirrus Model Intercomparison Project

Contact: Andreas Muhlbauer

CMIP investigates the microphysical and macrophysical evolution and life cycle of a synoptically-driven cirrus and to compare simulated cirrus cloud properties and radiative effects among models.

Grey Zone Project: Cold Air Outbreak Intercomparison Case

Contact: Pier Siebesma

The goals of the Grey Zone Project is to systematically explore the capability of climate and weather models to represent cloud and convective processes in the resolution range between 1 and 10 km (the so called grey zone) in support of the development of scale adaptive parameterizations for these processes. As a first activity, a comprehensive intercomparison case for a cold air outbreak such as observed during the CONSTRAIN field campaign has been developed.

Other GASS Projects

Continuous Intercomparison of Radiation Codes

Contacts: Lazaros Oreopoulos and Eli Mlawer

CIRC is intended as an evolving and regularly updated reference source for evaluation against “line-by-line” standards of radiative transfer codes used in Global Climate Models and other atmospheric applications. CIRC differs from previous intercomparisons in that it relies on an observationally validated catalogue of cases. It is currently completing Phase I.