Our project will utilize recent advances in the analysis of high-resolution satellite data for studies of the full three-dimensional (3D) properties of orographic gravity wave (OGW) events, and evaluation of existing and new parametrizations of OGW drag in global models. We will bring together an international team of experts on (1) the satellite data and their analysis, (2) high-resolution wave-resolving models, (3) global prediction models, and (4) parametrization methods.
OGW drag is one of the fundamental physics parametrizations employed in every global prediction model across timescales from weather to climate. Orographic waves are part of the complex dynamical interaction of winds with topography, and one piece in the puzzle that is topography's effect on global circulation. Parametrized OGW drag provides an important control on model wind biases at levels from the surface through the middle atmosphere, and these alterations in winds in turn affect stationary and synoptic Rossby wave propagation and dissipation. Thus properly tuned OGW drag parameterzations can improve weather model prediction skill from synoptic to seasonal timescales [Sigmond et al. 2013; Shaw et al. 2014]. Climate models have long relied on OGW drag for improved representations of both the mean climate and variability [Alexander et al. 2010]. In the stratosphere in particular, the circulation changes associated with OGW drag reduce winter temperature biases that affect ozone chemistry, so OGW drag is also fundamental to chemistry-climate modelling [Eyring et al. 2010]. Despite its importance in global models, OGW parametrization tuning is still only weakly constrained by observations in today's models, while new issues related to shortcomings in OGW parametrization are arising.
At ISSI Bern, we will perform the difficult task of determining uncertainties in existing observations and parametrization methods, and evaluating new state-of-the-art techniques for representing OGW drag in global models. Our members are all actively working on projects that will feed the team's joint work. Several members provide links to relevant international projects within the World Climate and World Weather Research Programmes (WCRP and WWRP), ensuring the team's results will be disseminated for broad scientific impact.
Top: Wright et al, ACP 2017
Middle: Hoffmann et al, JGR 2013
Bottom: Ern et al, GRL 2016