Improving the accuracy of climate prediction models has become a crucial activity for Earth scientists in the 21st century because of the profound social impacts of climate change. In particular, the role of stratospheric processes on climate have been highlighted in many recent studies. These include the effects of stratospheric dynamical processes on short term and seasonal forecasts at extratropical latitudes and decadal-scale changes in ozone on the Southern Hemisphere circulation, ocean currents, and carbon uptake.
With the acceptance of a well-resolved stratosphere for accurate seasonal and regional climate change descriptions in global models, a realistic treatment of gravity waves of all types is recognized as important both for climate and long-range weather forecasting applications. Two key needs for climate modelling in the present era are: (1) reducing model wind biases with improved estimates of gravity wave forces, and (2) improving methods for specifying gravity wave sources that are physically justifiable. We therefore will propose two workshops to focus on each of these two topics: Forces and Sources. The workshops will start with an examination of zonal mean forces and evolve to regional studies, with one focus on the tropics and tropical convection, and a second focus on the Southern Hemisphere’s mountain and jet sources.
The modern era of satellite data observations wedded with modern data assimilation system tools are leading to exciting new methods for estimating gravity wave forces in the middle atmosphere, but the results are in their infancy, and are not yet influencing global modelling methods. Global models are also evolving at a rapid pace, with improvements in resolution that allow the direct simulation of a significant portion of the gravity wave spectrum, while other portions still unresolved are parameterized. However, a methodology for adjusting parameters with resolution is lacking. These developments are driving our study. Our team includes experts in data assimilation, global forecasting models, climate models and observational analyses. The team members will bring a wide variety of different model systems, methods, and observational analyses to ISSI for direct intercomparison. We expect two to three review papers to result from these ISSI workshops. It is also possible that the discussions among this international team of researchers working at the forefront of the field may define a next generation approach to the problem of gravity wave effects in global models.