Pacific-North American teleconnection

Pacific-North American teleconnection
Name	Pacific-North American teleconnection
Abbreviation	PNA
Domain	Atmosphere–ocean interaction
Region	North Pacific; North America
First described	1970s

Pacific-North American teleconnection

The Pacific-North American teleconnection is a prominent large-scale atmospheric pattern linking circulation anomalies over the North Pacific Ocean, the Aleutian Islands, the Gulf of Alaska, the Rocky Mountains, and the North American Cordillera. It modulates wintertime storm tracks influencing climate over the United States, Canada, and parts of Mexico, and interacts with other modes such as the El Niño–Southern Oscillation, the Pacific Decadal Oscillation, and the Arctic Oscillation.

Overview

The PNA manifests as a quadrupole of geopotential height anomalies centered near the Hawaiian Islands region, the Aleutian Low, the Gulf of Alaska ridge, and the Great Lakes or Sierra Nevada sector, producing teleconnected impacts from the Aleutian Islands to the Appalachian Mountains and the Great Plains. It was characterized in observational analyses by researchers associated with institutions such as NOAA, the National Center for Atmospheric Research, and university groups including University of Washington and Scripps Institution of Oceanography. The pattern is frequently described alongside canonical indices used in studies conducted by groups at NASA, the Environment and Climate Change Canada, and international projects like the World Meteorological Organization initiatives.

Mechanism and Dynamics

Dynamically, the PNA arises from tropically forced Rossby wave trains originating in the tropical Pacific and refracted by the mean flow and sea surface temperature anomalies near the Equator, with source regions tied to convective variability over the Indo-Pacific Warm Pool and the Intertropical Convergence Zone. Waveguide theory connects forcing over the Marianas Islands and the Philippine Sea to downstream responses near the Aleutian Islands and the British Columbia coast via stationary Rossby wave propagation studied in frameworks developed at Princeton University and Massachusetts Institute of Technology. Atmospheric blocking near the Aleutian Islands and downstream ridge-trough interactions over the Pacific Northwest and California are modulated by jet stream shifts documented in work from NOAA ESRL and the Met Office.

Climate Impacts and Variability

Positive and negative phases of the PNA correlate with surface temperature and precipitation anomalies over populous regions including California, the Southwest United States, the Midwest United States, and southern Alberta. A positive phase often coincides with enhanced ridging near the Gulf of Alaska, promoting warm, dry conditions in Alaska and the Pacific Northwest while directing storms into the Gulf Coast and Southeastern United States, with socioeconomic implications for entities like the Federal Emergency Management Agency and agricultural sectors represented by the United States Department of Agriculture. Interannual modulation by phenomena such as El Niño, La Niña, the Madden–Julian Oscillation, and low-frequency shifts like the Pacific Decadal Oscillation influences extremes that affect infrastructure overseen by agencies like the U.S. Geological Survey and Transport Canada.

Observational Evidence and Indices

Observational identification of the PNA relies on empirical orthogonal function analyses and rotated principal components applied to geopotential height fields from reanalyses produced by ECMWF, NCEP, and research products from JMA. The canonical PNA index is computed from standardized 500 hPa height anomalies at nodes often referenced to locations such as the Aleutian Islands, Hawaii, the Rocky Mountains, and the Great Lakes region, with long-term diagnostics archived by NOAA National Centers for Environmental Information and synthesized in assessments by the Intergovernmental Panel on Climate Change. Paleoclimate proxies from tree rings in the Sierra Nevada and lake sediments near the Great Plains provide multi-century context that complements satellite-era records from NOAA satellites and instruments operated by NASA.

Modeling and Predictability

Climate models from the Coupled Model Intercomparison Project ensembles, including models developed at institutions such as GFDL, Hadley Centre, and Canadian Centre for Climate Modelling and Analysis, simulate PNA-like variability with varying fidelity tied to representation of tropical convection and extratropical wave propagation. Seasonal forecasting systems run by NOAA Climate Prediction Center and international centers like the European Centre for Medium-Range Weather Forecasts exploit PNA predictability emerging from persistent sea surface temperature anomalies associated with El Niño–Southern Oscillation, while high-resolution regional experiments at Lawrence Livermore National Laboratory and universities test sensitivity to land surface schemes impacting teleconnection strength.

Teleconnection Interactions and Modulation

The PNA does not act in isolation: it interacts with the Arctic Oscillation, the North Atlantic Oscillation, and tropical modes such as the Indian Ocean Dipole and ENSO Modoki, producing compound effects over regions including California, the Canadian Prairies, and the Northeastern United States. Teleconnection superposition can amplify or cancel regional impacts, complicating attribution tasks undertaken by researchers at IPCC-affiliated working groups and national research programs like NSF-funded projects and cooperative studies involving NOAA and Environment and Climate Change Canada.

Category:Atmospheric teleconnections