Title: Seasonal Tropical-Extratropical Teleconnections Originating from Tropical Rainfall Modes Independent of the Niño 3.4 Index in Northern Winters
Lecturer: Dr. Peitao Peng (NOAA)
Time: Tuesday April 16, 2024 at 10:00 AM
Venue: Lecture Hall D103, School of Atmospheric Sciences
Abstract: 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 Niño 3.4 index for northern winters. The mode decomposition for tropical rainfall is done by first removing the Niño 3.4 index related variability 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 anomalies corresponding to the rainfall modes are forced response to the corresponding rainfall mode. The teleconnection patterns reveal some new features and show that some intrinsic mid-latitude 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 Niño 3.4 index and linear trend, are applied to the attribution analyses for the global circulation anomalies of 2019/2020 winter and the California dry condition during the strong El Niño winter of 2015/2016. The overall impact of these modes in the period of 1980-2021 is also discussed.