Tropical Moisture Exports, Extreme Precipitation and Floods in Northeast US

Abstract. A statistically and physically based framework is put forward that investigates the relationship between Tropical Moisture Exports (TME), and extreme Precipitation and floods in the Northeast United States (N.E. USA). TME correspond to the meridional transport of moist air masses, primarily born in tropical oceanic areas, to higher latitudes; contribute to the global climatology precipitation and its extremes; and are closely related to flood events, especially in the mid-latitudes. The birth process and the steering of TME have seasonal and interannual variability. In this study, we explore how the TME are related to extreme precipitation and floods in the N.E. USA with a focus on seasonal variability and the potential impact of the El Niño Southern Oscillation. Links of TME to large floods events in N.E. USA in different seasons are first identified. The major moisture sources of the TME that contribute to precipitation extremes and floods in N.E. USA are then identified, together with the seasonally and interannually varying characteristics in terms of both TME birth and entrance to the N.E. USA, and their subsequent contribution to extreme precipitation. We show that the extreme daily precipitation events are dominated by extreme TME entering the N.E. USA events in every season.