Friday, May 09, 2008

Cool cool San Francisco

It's been a cool San Francisco spring, wind heavy with warm days seemingly few and far between. My search for an explanation, even a mention came up with nothing, but then I came across the Pacific Decadal Oscillation (PDO).

Apparently, we are coming into a cool cycle of this oscillation (this is disputed) which was discovered not long ago by scientists (Steve Hare, Nathan Mantua, Yuan Zhang, Robert Francis and Mike Wallace) studying Salmon populations. Swings in Salmon populations are often tied to this oscillation.

If you are saying, "Wait, Salmon populations? Didn't the Salmon population just collapse?" That's what I said when I read more about it. The studies here and here need some serious help from someone whose read Tufte. I think the data shows that in the past some populations of salmon go down when the PDO is in the cool phase. Strangely, I cannot find any mention of it recently, not in connection to our weather. You would have thought someone would have brought it up at all those hearings.

The PDO apparently could lead to more drought in Southern California. It intensifies El Ninas and moderates El Ninos. The Jet stream is steered north by this though, so I'm not sure if it is actually tied to our cool wave. But perhaps it is too. Liz will not be pleased.

Weather sure is a complicated thing.

Labels: , ,