Abstract

Climate model fidelity in representing ENSO-induced teleconnection is assessed with process-oriented di-agnostics that examine a chain of processes, from equatorial Pacific precipitation to the midlatitude circulation pattern over the Pacific-North American regions. Such processes are rarely addr... Show moreClimate model fidelity in representing ENSO-induced teleconnection is assessed with process-oriented di-agnostics that examine a chain of processes, from equatorial Pacific precipitation to the midlatitude circulation pattern over the Pacific-North American regions. Such processes are rarely addressed during model development. Using an upper-tropospheric divergent level, local vorticity gradient of the ambient zonal flow (partial derivative U-2/partial derivative y(2)) and a restoring force for Rossby waves (beta(*)) are estimated, the equivalent barotropic vorticity equation is solved, and an anomalous Rossby wave source (RWS') quantified. The analysis is applied to AMIP5 and AMIP6 simulations. For a realistic circulation response representation, the hypothesis that models accurately represent the strength and location of RWS', and spatial variations in beta(*) is tested. Compared to AMIP5, in AMIP6 there are clear improvements in representing RWS' and beta(*). To validate the hypothesis, the analysis identifies two metrics: spatially coherent RWS' in the subtropical North Pacific, and longitudes of negative beta(*) over the western-central North Pacific. By projecting these metrics in two and three-dimensional views, improvements or degradations in model versions are apparent. If a model's fidelity in representing partial derivative U-2/partial derivative y(2) and RWS' are compromised, then radiated Rossby waves are reflected more equatorward, resulting in zonally elongated circulation anomalies over the central North Pacific. Thus, during climate model development, applying this analysis frequently will keep a regular check on the fidelity of the modeled response to anomalous El Nino convection in conjunction with changing model ambient flow dependencies. This analysis is intended to form a process-oriented diagnostics package, a community contribution to the NOAA Model Diagnostics Task Force. Show less