On Friday, October 6th, we will have an OCP Seminar given by Dr. Jhordanne Jones, a NOAA Climate and Global Change Postdoctoral Fellow.
This will be a hybrid in-person/zoom seminar taking place in the Monell Auditorium. Please email the event contact for the zoom information. The title and abstract are provided down below.
Title: Interbasin versus intrabasin sea surface temperature forcing of the Western North Pacific subtropical high's westward extensions
Abstract: Zonal extensions of the Western Pacific subtropical high (WPSH) strongly modulate extreme rainfall activity and tropical cyclone (TC) landfall over the Western North Pacific (WNP) region. On seasonal timescales, these zonal extensions (a westward extension or eastward contraction) are forced primarily by inter-basin zonal sea surface temperature (SST) gradients. However, despite the presence of large-scale zonal SST gradients, the WPSH's response to SSTs varies from year to year. In this study, we force the atmosphere-only NCAR Community Earth System Model version 2 (CESM2) simulations with two real-world SST patterns (COMP1 and COMP2), both featuring the large-scale zonal SST gradient characteristic of decaying El Niño/developing La Niña summers. For each of these patterns, we examine the relative contributions of local and remote SST forcings to the forced westward extensions over the WNP during June-August. Our results indicate that the subtle differences between the two SST patterns belie significant differences in how the westward extensions are forced. In the COMP1 SST pattern, characterized by remnant decaying El Niño SST anomalies, the descending arm of the Pacific Walker Circulation is bolstered by tropical North Atlantic and North Indian basin SSTs. In contrast, for the COMP2 SST pattern, the descending Walker Circulation arm is driven by widespread cold anomalies throughout the central and eastern Pacific basin, resulting in a predominant intrabasin forcing. The results of this study have implications for understanding and predicting the impact of the WPSH's zonal variability on tropical cyclones and extreme rainfall over the WNP.