Relationships between the pacific/north american teleconnection patterns and precipitation events in the south‐eastern USA

Abstract

Precipitation event attributes, defined as the amount, duration, and frequency of individual rainstorms, vary considerably from place to place and season to season. Event variability is caused by a combination of large-scale and local climate processes. Correlations of seasonal time series show that the Pacificmorth American (PNA) teleconnection pattern and local rainfall event attributes are significantly related in specific areas of the south-eastern USA in some seasons. Shifts in the zonal/meridional flow over North America affect both the number of events and the event size. The total number of events in some regions changes by as many as 10 to 12 events per season with shifts in continental-scale circulation. An analysis of attribute distributions shows that the percentage of total events falling into selected intensity categories may also change by as much as 10 per cent between flow regimes. Relationships have both temporal and spatial patterns. Shifts in continental-scale circulation affect event attributes most strongly in winter, with more events occurring in zonal years. Events with greater amounts and durations are found east of the Appalachians in meridional years and west of the mountains in zonal years.

Multi-century variability in the Pacific North American circulation pattern reconstructed from tree rings

“…1b, c). During the RPNA, the mean position of the polar front jet stream over the eastern USA is displaced further north than average promoting more frequent intrusions of maritime tropical air from the Gulf of Mexico and increasing precipitation (Archambault et al 2008;Henderson and Robinson 1994) and temperature over the region. Nearly zonal westerly flow off the North Pacific during RPNA directs Pacific storms and polar air intrusions towards the northwestern USA.…”

Climatic Relationships to Chesapeake Bay Salinity During Southern Oscillation Extremes

“…The statistically significant temporal increase in the NAO index (r = .20; P|r| = .0014) and the confinement of significant long-term salinity changes to the surface layer provide evidence that circulation and precipitation changes in the eastern United States may help to explain the linear temporal trend toward decreasing surface CB salinity. Vega et al (1998b) found significant increases in both southeast and northeast regional precip- The positive (negative) phase of the SOI is typically associated with a negative (positive) PNA pattern (Yarnal, 1985), producing negative (positive) precipitation departures in the southeastern United States (Leathers et al, 1991;Henderson and Robinson, 1994;Henderson and Vega, 1996), but insignificant correlations farther north along the Atlantic Coast. The absence of significant correlations between the PNA pattern and CB salinity may reflect the position of the CB in the northeastern climate region, or in the transition zone (Yarnal and Leathers, 1988) between the northeastern and southeastern United States precipitation regions.…”

Decadal-Scale Trends in Transition Weather Types and Atmospheric Circulation

“…Variations in PNA alter the ridge-trough structure that persists over these regions, which consequentially significantly impact surface climate across much of the country (e.g., Henderson and Robinson 1994, Leathers et al 1991, Skeeter and Parker 1985. Sheridan (2003) and Knight et al (2008) both observe significant correlations between the PNA index and transition frequencies over the past several decades.…”

“…Subsidence aids warming due to compressional heating (Leathers et al, 1991). In the east, positive PNA years result in the jet stream being diverted further to the south, increasing jet stream activity and precipitation over Florida and decreasing them to the north (Henderson and Robinson 1994). While precipitation is lower, arctic air is able to penetrate south much more easily, resulting in lower temperatures as well (e.g., Leathers et al 1991).…”

“…While precipitation is lower, arctic air is able to penetrate south much more easily, resulting in lower temperatures as well (e.g., Leathers et al 1991). The negative phase is associated with fewer winter storms in the southeastern states, and more summertime storms (Henderson and Robinson 1994) The PNA does not emerge from analysis of surface data over the same domain because of the complications in the pressure data that arise because of the complicated topography in the western United States (Leathers et al 1991). However, a robust pattern of variability does emerge over the Pacific region that is similar in nature to the North Atlantic Oscillation, also originally identified by Walker and Bliss (1932).…”