Seasonal Tropical-Extratropical Teleconnections Originating from Tropical Rainfall Modes Independent of the Nino-3.4 Index in Northern Winters

This study, based on an analysis with observational and reanalysis data, highlights seasonal tropical- extratropical atmospheric teleconnections originating from tropical rainfall modes unrelated to the Nino-3.4 index for northern winters. The mode decomposition for tropical rainfall is done by first removing the Nino-3.4 index-related vari-ability from the tropical rainfall and then applying rotated empirical orthogonal function (REOF) analysis to the residual. The corresponding teleconnection patterns are obtained by regressing global atmospheric fields against the time series of the rainfall modes. Analyses of the tropical heating-atmospheric circulation relationship indicate that the circulation anom-alies corresponding to the rainfall modes are forced responses to the corresponding rainfall mode. The teleconnection pat-terns reveal some new features and show that some intrinsic midlatitude patterns can be triggered by tropical forcing with different rainfall patterns. Results from this study are relevant to seasonal climate attribution and prediction analyses and climate model evaluation. As an illustration, the teleconnections from the rainfall modes, together with that related to the Nino-3.4 index and linear trend, are applied to the attribution analyses for the global circulation anomalies of 2019/20 win-ter and the California dry condition during the strong El Nino winter of 2015/16. The overall impact of these modes in the period of 1980-2021 is also discussed.