On a Cloudy Day - The Role of Clouds in Global Climate Design and Testing of a Global Cloud-Resolving Model David A. Randall (project webpage) Colorado State University

The grand challenge for climate modeling is to predict future climates based on scenarios of anthropogenic emissions and other changes resulting from options in energy policies. This SciDAC project will develop and test a global cloud resolving model (GCRM), i.e., a global atmospheric circulation model with a grid-cell spacing of approximately 3 km, capable of simulating the circulations associated with large convective clouds. The GCRM developed in this project will make use of a geodesic grid, building on methods developed under SciDAC-1. It will use a non-hydrostatic dynamical core, based on methods already used in limited-area modeling by the team, and will be based on an appropriate physical formulation, including non-hydrostatic dynamics and parameterized cloud microphysics. This requires horizontal resolution on the order of a few km or better, and time steps small enough to resolve the growth and decay of individual large clouds. It must also be formulated using numerical methods that are suitable for cloud scales as well as large scales. As a result the GCRM will require significant computing resources, and must use those resources effectively. Applications of the GCRM within the lifetime of the proposed Cooperative Agreement will include:

• deterministic weather prediction over a few simulated days, within the framework of CAPT, an experimental weather forecasting project created by DOE for the purpose of testing climate models;
• simulations on the order of one month for studying “climate drift”;
• simulations on the order of one year, including simulations in which the GCRM is coupled with an ocean model, for the purpose of testing the GCRM’s potential for producing realistic climate simulations.

True climate simulations with the GCRM will not be computationally feasible within the lifetime of the proposed research. Nevertheless, the recent progress in computational power has made it possible now to begin learning how to build and use GCRMs.

The Department’s Atmospheric Radiation Measurement (ARM) program was created to help resolve scientific uncertainties related to global climate change, with a specific focus on the crucial role of clouds and their influence on radiative feedback processes in the atmosphere. The primary goal of the ARM program is to improve the treatment of cloud and radiation physics in global climate models in order to improve the climate simulation capabilities of these models. ARM's scientists research a broad range of issues that span remote sensing, physical process investigation and modeling on all scales. This project will advance these efforts by advancing the development of global cloud resolving models.

Science Application: Climate Modeling and Simulation

Project Title: Design and Testing of a Global Cloud-Resolving Model

Principal Investigator: David A. Randall
Affiliation: Colorado State University

Project Webpage: http://kiwi.atmos.colostate.edu/gcrm/

Participating Institutions and Co-Investigators:
Colorado State University - David A. Randall (PI), Joon-Hee Jung, Celal Konor, Ross Heikes, and Charlotte DeMott
Pacific Northwest National Laboratory - Karen Schuchardt, George Chin, Annette Koontz, Roger Marchand, Bruce Palmer
University of California at Los Angeles - Akio Arakawa (Co-PI)

Funding Partners: Office of Science — Office of Advanced Scientific Computing Research, and Office of Biological and Environmental Research

Budget and Duration: Approximately $1.2 million per year for five years ¹

Other SciDAC climate efforts