Posted: January 21, 2008

CIRES Space Weather Scientists and EMC Develop Whole Atmosphere Model

Global atmospheric modeling may reach new horizons, thanks to the development of a Whole Atmosphere Model known familiarly as WAM, which is part of the Integrated Dynamics through Earth's Atmosphere (IDEA) project. Designed and tested by Rashid Akmaev, Tim Fuller-Rowell, and their colleagues at the Cooperative Institute for Research in Environmental Sciences (CIRES) and NOAA's Space Weather Prediction Center, together with Mark Iredell and colleagues from the Environmental Modeling Center (EMC), WAM is composed of 150 vertical layers and extends from the ground to the top of the thermosphere, a distance of about 600 kilometers, which is more than 10 times higher than most global circulation models in use today. The team compared results from a 15-month run of WAM with lower thermosphere observations from the TIMED satellite and found the new model successfully reproduced seasonal variability of tidal waves recently implicated in the observed variability of the upper atmosphere.

Background
WAM is based on the National Weather Service's Global Forecast System (GFS) model. Like the GFS model, WAM has a spectral dynamical core that includes radiative processes, a hydrological cycle, a planetary boundary layer, and surface exchange processes. In addition, WAM simulates the horizontal, molecular transport of momentum and heat, as well as the transport and mixing of atmospheric species along and across pressure surfaces. The new model also includes UV radiative heating, infrared radiative cooling, and non-orographic gravity waves. WAM has a T62 spectral resolution, equivalent to 1.8°?x 1.8°?in latitude-longitude.

Significance
Observations suggest that lower atmosphere dynamics influence the spatial morphology of the upper atmosphere, including the ionosphere. Recent studies have attempted to identify whether atmospheric tides, modulated by planetary wave activity, are involved in transferring energy from the lower atmosphere upwards. An advanced modeling tool, such as WAM, can help quantify connections between terrestrial and space weather and will eventually improve upper atmosphere forecasting skills, important for GPS navigation and communications.