Recent developments in gravity-wave effects in climatemodels and the global distribution of gravity-wavemomentum flux from observations and models

Recent observational and theoretical studies of the global properties of small-scale atmospheric gravity waves have highlighted the global effects of these waves on the circulation fromthe surface to the middle atmosphere. The effects of gravitywaves on the large-scale circulationhave longbeen treated via parametrizations in both climate and weather-forecasting applications. In these parametrizations, key parameters describe the global distributions of gravity-wave momentum flux, wavelengths and frequencies. Until recently, global observations could not define the required parameters because thewaves are small in scale andintermittent in occurrence. Recent satellite and other global datasets with improved resolution, along with innovative analysismethods, arenowproviding constraints for theparametrizations that can improve the treatment of thesewaves in climate-prediction models. Research using very-highresolution global models has also recently demonstrated the capability to resolve gravitywaves and their circulation effects, andwhentested against observations these models show some very realistic properties. Here we review recent studies on gravitywave effects in stratosphere-resolving climate models, recent observations and analysis methods that reveal global patterns in gravity-wave momentum fluxes and results of very-high-resolution model studies, and we outline some future research requirements to improve the treatment of these waves in climate simulations.