Research about wind flow patterns in the atmosphere advances our understanding of extreme weather events, which, when accurately forecasted, can save lives, support emergency services, and help to make mitigation efforts more effective. One challenge in these models is representing how wind direction veers at different heights as a result of friction at Earth’s surface, or “wind-turning.” Within the planetary boundary layer (PBL), the layer of the atmosphere closest to Earth’s surface, we understand relatively little about wind turning, yet it is clear that it has impacts on larger atmospheric and oceanic flow.
A new study, supported by the Climate Program Office’s Climate Variability & Predictability (CVP) Program, evaluates eight models participating in the Coupled Model Intercomparison Project version 6 (CMIP6), to see how accurately they estimate wind-turning angles in the PBL compared to observations. Stockholm University scientists Joakim Pyykkö and CVP-supported researcher Gunilla Svensson found that wind-turning angles are underestimated in all eight models, with the NOAA Geophysical Fluid Dynamics Laboratory’s CM4.0 physical climate model giving the closest results to the observations. These results, published in an early online release in The Journal of Climate, provide important context to how CMIP6 models reproduce wind-turning processes, and the authors go on to describe changes to the model that can yield more realistic outcomes. This project was made possible through an international partnership, and future work will focus on the mechanisms causing the underestimation in the models. This work is part of the Climate Process Teams (CPT), a partnership between NOAA’s CVP Program, the National Science Foundation (NSF), and the Department of Energy (DOE). These CPT projects aim to improve how ocean and atmospheric processes are represented in climate models.