Pacific North America pattern

Pacific North America pattern
Name	Pacific North America pattern
Abbreviation	PNA
Type	atmosphere_teleconnection
Domain	North_Pacific Ocean; North_America
Seasonality	winter; spring; autumn
Related	Aleutian_Low; Pacific_Decadal_Oscillation; El_Niño–Southern_Oscillation

Pacific North America pattern is a prominent atmospheric teleconnection that links circulation anomalies over the North Pacific Ocean, Aleutian Islands, Gulf of Alaska and western and eastern parts of North America. It modulates storm tracks, temperature and precipitation across regions including the Pacific Northwest, Southwestern United States, Great Plains, Eastern Seaboard and parts of Canada and Mexico. The pattern interacts with other modes such as El Niño–Southern Oscillation, the Arctic Oscillation and the North Atlantic Oscillation, and is actively studied by institutions like National Oceanic and Atmospheric Administration, NOAA, University of Washington and the Scripps Institution of Oceanography.

Overview

The pattern was identified in observational analyses by researchers at Geophysical Fluid Dynamics Laboratory, National Center for Atmospheric Research, and the University of Colorado Boulder and described using empirical orthogonal function methods developed at Princeton University and Massachusetts Institute of Technology. It is often represented by a multi-pole pressure anomaly with centers near the Aleutian Low, the Gulf of Alaska and the southwestern United States, and is closely related to circulation features like the Pacific jet stream and the subtropical jet stream. Variants of the pattern are compared with the Pacific Decadal Oscillation and the Arctic Oscillation in analyses by agencies such as Environment and Climate Change Canada and the National Aeronautics and Space Administration.

Atmospheric dynamics and formation

Formation mechanisms invoke Rossby wave trains excited by convective anomalies over the tropical Pacific, forcing across the midlatitude Pacific toward North America in manners described by studies from Lamont–Doherty Earth Observatory and NOAA's Climate Prediction Center. Tropical forcing associated with El Niño and La Niña phases of the El Niño–Southern Oscillation alters the amplitude and phase via interactions with the Aleutian Low and the Bering Sea. Wave-mean flow interactions described in textbooks from Cambridge University Press and modeling work at European Centre for Medium-Range Weather Forecasts and Met Office show that jet stream configuration, blocking over the North Atlantic, and upstream Pacific storms such as those tracked by Joint Typhoon Warning Center modulate pattern development.

Climatic impacts and teleconnections

Teleconnections link the pattern to surface climate across regions monitored by Environment Canada, Servicio Meteorológico Nacional (Mexico), US Geological Survey, and regional utilities. Positive phases correlate with warm anomalies over the Southwestern United States and cold anomalies across the Southeast Alaska and the Great Lakes in analyses by NOAA National Climatic Data Center and National Snow and Ice Data Center. The pattern influences drought monitored by U.S. Drought Monitor, wildfire seasons overseen by U.S. Forest Service, and precipitation extremes examined in reports by Intergovernmental Panel on Climate Change and World Meteorological Organization.

Variability and long-term trends

Interannual variability is tied to El Niño–Southern Oscillation and modulated by decadal changes such as the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation as demonstrated in long-term reconstructions from PAGES and paleoclimate records held at Smithsonian Institution and United States Geological Survey. Trends in the pattern have been evaluated in climate model intercomparisons like CMIP5 and CMIP6 coordinated by World Climate Research Programme, with attribution studies from IPCC authors and climate centers including NOAA GFDL, Met Office Hadley Centre and Canadian Centre for Climate Modelling and Analysis.

Observation, indices and modeling

Indices for the pattern are computed from reanalyses such as ERA-Interim, ERA5, NCEP/NCAR Reanalysis and observational datasets compiled by ICOADS and the Hadley Centre. Statistical techniques from University of Reading and machine-learning approaches from Stanford University and Massachusetts Institute of Technology are used to forecast the index together with dynamical forecasts from European Centre for Medium-Range Weather Forecasts, NOAA's Global Forecast System and regional models run at National Center for Atmospheric Research. Monitoring is performed by agencies including NOAA Climate Prediction Center, Environment and Climate Change Canada, and research groups at Scripps Institution of Oceanography and University of British Columbia.

Regional effects and impacts on weather-events

Regionally, the pattern has been linked to altered cyclone tracks affecting ports like Seattle, San Francisco, Los Angeles and Vancouver, and to snowpack variability in basins managed by Bureau of Reclamation and California Department of Water Resources. It modulates heat waves impacting cities such as Phoenix, Las Vegas, Denver, and Chicago, and affects agricultural regions including California's Central Valley, Okanagan Valley and the Great Plains. Impacts on ecosystems and infrastructure have been documented in case studies by US Forest Service, National Park Service, California Department of Fish and Wildlife and international assessments by United Nations Environment Programme.

Category:Atmospheric teleconnections