Subtropical PV Streamer Variability and Impact in the Subtropical North Atlantic Basin

Subtropical potential vorticity (PV) streamers are elongated filaments of high PV air that can serve as conduits for tropical-extratropical air mass exchange. These PV streamers often originate from anticyclonic Rossby wave breaking (AWB), where upstream low PV is advected poleward over downstream high PV air at the tropopause. This evolution results in an elongated, positively tilted PV streamer that also represents a distinct upper-tropospheric trough. Frequent occurrence of PV streamer formation in conjunction with AWB contributes to the climatologically observed mid-ocean trough (MOT) in the subtropical North Atlantic (NATL) basin, where MOTs govern climatological corridors of high vertical wind shear, low upper-tropospheric thickness, and moisture dipoles in the NATL basin. These environmental factors are known to influence both frequency and pathway of tropical cyclogenesis (TCG) in the NATL basin. As a consequence, this study aims to understand how differences in PV streamer characteristics impact the environment of the NATL basin and subsequently how these variations in seasonal PV streamer characteristics impact changes in climatological TCG pathways. PV streamers are identified from combining prior methodologies in order to link meridional gradient reversals in 350 K PV (defining AWB) to elongated filaments of high PV (defining the PV streamer) using Climate Forecast System Reanalysis data. The top and bottom 20% of the cumulative intensity distribution of PV streamers will be identified. Composite differences of these two sets of cases will be constructed to evaluate how the surrounding environment varies depending on PV intensity. Finally, PV streamer cases will be integrated over the TC season to illustrate how PV streamer frequency relates to the number of baroclinic and nonbaroclinic TCs that occur in a season.