Detailed Record



Understanding the Cascade: Removing GCM Biases Improves Dynamically Downscaled Climate Projections


Abstract Polarization surrounding bias correction (BC) in creating climate projections arises from its lack of physicality. Here, we perform and analyze 18 dynamical downscaling simulations (with and without BC) to better understand the physical impacts of BC, applied before downscaling, on regional climate output across the western United States. Without BC, downscaled precipitation is systematically and unrealistically wet biased compared to a hierarchy of observationally based datasets over the 1980–2014 period due to cascading mean‐state Global Climate Model (GCM) biases: (a) overly strong lower‐tropospheric lapse rates (5 K/km), (b) overly cold (2 K) tropospheric temperatures, and (c) anomalous mid‐tropospheric cyclonic vorticity advection. With BC, downscaled precipitation (snow) biases are virtually eliminated (halved). Identified GCM biases are common to the broader Coupled Model Intercomparison Project ensemble. Physical effects of BC on the quality of the regionalized projections, pending an evaluation of BC's distortion of the downscaled climate response, may motivate its broader application by dynamical downscalers.
Authors Stefan Rahimi University of WyomingORCID , Lei Huang ORCID , Jesse Norris ORCID , Alex Hall ORCID , Naomi Goldenson ORCID , Mark D. Risser ORCID , Daniel Feldman ORCID , Zachary J. Lebo ORCID , Eli Dennis ORCID , Chad W. Thackeray ORCID
Journal Info American Geophysical Union | Geophysical Research Letters , vol: 51 , iss: 9
Publication Date 5/4/2024
ISSN 0094-8276
TypeKeyword Image article
Open Access hybrid Hybrid Access
DOI https://doi.org/10.1029/2023gl106264
KeywordsKeyword Image Climate Modeling (Score: 0.564923) , Probabilistic Forecasting (Score: 0.527036) , Mesoscale Modeling (Score: 0.515698) , Atmospheric Dynamics (Score: 0.513673)