Development of process-oriented metrics for ENSO-induced teleconnection over North America and U.S. Affiliated Pacific Islands in Climate models

“In climate models, to demonstrate the hypothesis that the sea surface temperature (SST) anomalies associated with ENSO serves as the source predictability of seasonal to interannual climate anomalies over North America and U.S. affiliated Pacific Islands (USAPI) require translating these SST anomalies into precipitation and latent heating anomalies by models’ physical parameterizations. While CMIP5 (Coupled Model Intercomparison Project Phase 5) assessment studies suggest certain improvement in representing ENSO-related SST anomalies, representation of precipitation anomalies along the equatorial central Pacific and therefore tropical to extratropical teleconnection have not improved. Climate models’ fidelity in representing ENSO and associated teleconnection require detailed assessment of models’ ability in representing “moist convective processes”. Specifically, during the life-cycle of ENSO, a detailed evaluation of various entropy elements in forcing convection and factors that determine vertical structure of diabatic heating (such as cloud intensity and height) needs to be performed. Such a process-oriented diagnostics will lead to identification of source of model errors and provide pathways for model improvement.

We propose processes-oriented metrics to be applied on the 45+ CMIP5 models as well as on the hindcasts performed with the North American Multi-Model Ensemble Phase 2 (NMME-2). To assess observational uncertainty, similar metrics will be obtained from all available reanalysis products (CFSR, NCEP, ERA-Interim, JRA-25 and MERRA). We identify 4 major objectives that deem highly relevant to the present focus. Diagnostics are developed to understand: (i) processes that shape tropical precipitation climatology; (ii) processes in determining precipitation anomalies during different phases of ENSO and their different roles between equatorial central vs eastern Pacific precipitation anomalies; (iii) processes that determine the vertical structure of diabatic heating anomalies and associated teleconnection, and (iv) processes that account for regional and remote precipitation anomalies. Deliverables include objectively oriented and physically based metrics for climate models’ performance in representing precipitation anomalies along the equatorial Pacific, North America and the USAPI.

Our goals lie in identifying sources of model errors in physical parameterization, and provide clear pathways for model improvement. Our proposed research targets the MAPP competition that focuses on “Process-oriented evaluation of climate and Earth system models and derived projections”. Specifically, the competition identified research focus – “Area A: Metrics for climate and Earth system model development”. Process-based diagnostics will lead to selection of a subset models could contribute to other crosscutting (RISA and National climate change assessment) programs of NOAA.”