The Atmospheric Forcing Index (AFI) utilizes standardized scores of the first component from a principal components analysis on the Aleutian Low Pressure Index (ALPI), Pacific Interdecadal Oscillation Index, and the northwesterly atmospheric circulation anomalies for the North Pacific (December through March). Positive values represent intense Aleutian lows, above average frequency of westerly and southwesterly winds, cooling of sea surface temperatures in the central North Pacific, and warming within North American coastal waters.
Correct citation: Gordon A McFarlane, Jacquelynne R King, Richard J Beamish, Have there been recent changes in climate? Ask the fish, Progress in Oceanography, Volume 47, Issues 2–4, 2000, Pages 147-169, ISSN 0079-6611, https://doi.org/10.1016/S0079-6611(00)00034-3.
Abstract: http://www.sciencedirect.com/science/article/pii/S0079661100000343