Understanding the Pacific Decadal Oscillation and Its Impact on Winter Storms in the United States

The Pacific Decadal Oscillation (PDO) is a long-term climate pattern in the North Pacific Ocean, characterized by shifts in sea surface temperatures (SSTs) that occur over 20 to 30-year cycles. These shifts significantly influence weather patterns, including winter storms, across the United States.

What Is the Pacific Decadal Oscillation?

The PDO is a recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. It is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal time scales. (en.wikipedia.org)

Phases of the PDO

The PDO alternates between two primary phases:

• Positive (Warm) Phase: During this phase, the western Pacific becomes cooler, and the eastern Pacific warms. This pattern is associated with a deepened and southward-shifted Aleutian Low, leading to warmer and more humid conditions along the U.S. West Coast. Consequently, regions like the Pacific Northwest and Alaska experience milder temperatures and increased precipitation. (en.wikipedia.org)

• Negative (Cool) Phase: In contrast, the western Pacific warms, and the eastern Pacific cools. This phase is linked to a weakened Aleutian Low, resulting in cooler and drier conditions along the U.S. West Coast. Areas such as the Pacific Northwest may experience colder temperatures and reduced precipitation during this phase. (en.wikipedia.org)

Impact of the PDO on Winter Storms

The PDO's influence on winter storms in the United States varies depending on its phase:

• During the Positive Phase: The deepened Aleutian Low enhances the transport of warm, moist air along the West Coast, leading to increased winter precipitation. This can result in more frequent and intense winter storms in regions like the Pacific Northwest and Alaska. (en.wikipedia.org)

• During the Negative Phase: The weakened Aleutian Low reduces the influx of warm, moist air, leading to cooler and drier conditions along the West Coast. Consequently, winter storms may be less frequent and less intense in these areas. (en.wikipedia.org)

Understanding the PDO's Role in Climate Variability

The PDO is a significant driver of climate variability in the North Pacific region. Its phases can modulate the intensity and frequency of winter storms, affecting not only weather patterns but also marine ecosystems and fisheries. For instance, the PDO's warm phase has been associated with increased salmon production in Alaska, while its cool phase has been linked to decreased production. (en.wikipedia.org)

Monitoring the PDO

Scientists monitor the PDO using sea surface temperature data and atmospheric pressure patterns. Understanding the current phase of the PDO helps meteorologists predict potential changes in weather patterns, including the likelihood of winter storms. However, predicting the exact timing and intensity of these storms remains complex due to the interplay of various climatic factors.

In summary, the Pacific Decadal Oscillation is a crucial component of the Pacific Ocean's climate system, with its phases significantly influencing winter storm patterns across the United States. By understanding the PDO, we can better anticipate and prepare for the impacts of these long-term climate variations.

Highlights:

• Ocean-Atmosphere Climate Indices | NOAA Fisheries
• Pacific Decadal Oscillation (PDO) - Met Office
• Pacific Decadal Oscillation (PDO) | El Niño/La Niña Watch & PDO – Ocean Surface Topography from Space