Pacific Decadal Oscillation
During some of our farmer meetings we have taken questions about the Pacific Decadal Oscillation. This page provides some basic information to illustrate what PDO is and how it effects you.
The Pacific Decadal Oscillation (PDO) causes sea surface temperature anomalies across the Pacific Ocean and has periods that can last 20-30 years. In the positive phase, sea surface temperatures increase all up and down the east side of the Pacific Ocean, while temperatures are slightly cooler on the western side. In the past decade or so, we have been experiencing the negative phase, which displays the opposite effects.
Positive PDO
When sea surface temperatures are abnormally cool in the interior North Pacific and warm along the Pacific Coast, and when sea level pressures are below average over the North Pacific, the PDO has a positive value. The waters along the equator are much warmer. This tends to create more El Nino-like weather patterns across the United States. See map below.
El Nino Weather Pattern
A Negative PDO
A negative PDO is the exact opposite of a positive one. When we are in a negative phase we have cooler waters on the west coast of the United States and along the equator. It looks and acts a lot like a La Nina a weather pattern. We are currently in a negative PDO.
La Nina Weather Pattern
Below you can easily see the differences between the positive and negative phases of the PDO. Part (C) Is a timeline that illustrates how the PDO goes back and forth between Positive (+) and Negative (-) PDO. Today we are in a negative PDO, it is a -1.98 which is strong. This means that the weather is more likely to resemble weather patterns that are normal to a La Nina.