Sunday, October 23, 2011

Head Scratching Time Begins

A couple of things came streaming through my social sites today...more precisely, I noticed them today...

KCRA3's @MarkFinan's tweet touting his "La Niña Explainer" on the  KCRA 3 Weather Facebook Page

I didn't know Finan had a weather page on facebook, so I searched and liked it. Here it's a good thumbnail sketch of a seriously complex system:

    "For those of you that didn't see my explanation of La Nina on the news last night, let me explain here. First the basics... La Nina refers to a period of cooler than average water in the equatorial Pacific. The cooler than average water can set or alter weather patterns for extended periods of time, like for a season. 
    Based on past episodes, there are tendencies that you can see when we have a La Nina in place. For some parts of the country, like the Southeast and the Pacific Northwest, those tendencies are pretty well defined. The Northwest has a very good chance of having a cool, wet winter. For our area the signals are very mixed. 
    Last year was a La Nina year and the water year was very impressive in NorCal. Sacramento finished with about 125% of average rain and the Sierra had about 200% average precipitation. 
    Not all years are like that for us. Some years come in pretty average and some come in very dry. 1975-76 was a La Nina season and was one of the driest years we have ever seen. Sacramento only picked up about 7 inches of rain that season, about 36% of average. 
    The problem is that there are more forces at work that [effect] the equatorial Pacific. There is the Arctic Oscillation, the North Atlantic Oscillation, the MJO, the PDO etc. All of these have some influence on our weather patterns at any given time. Research into these is ongoing so seasonal forecasting is still pretty iffy. 
    So the bottom line is we don't know what sort of Winter we'll have here in NorCal."

Our climate is like an onion in that there are many layers of driving forces that influence the climate in the long term and weather in the short term. You could call these drivers the "Alphabet Soup"...they are all acronyms: AO, ENSO, PDO, MJO, NAO for a start.

ENSO (El Niño Southern Oscillation) is like the onion's skin. It's on the surface and it's the first oscillation that casual observers discover, and it's the shortest period oscillation we've discovered. ENSO is home to El Niño and La Niña.

Mr Finan is right about the forecasting being "iffy", most of the dedevelopment of the computer forecasting models took place in the last 30 years or so...about the same time that the PDO was in the Positive Phase (read warm phase). Now that the PDO has crossed into negative territory, the models will have accuracy problems.

Clearly meteorologists haven't yet found the mechanism that drives Central California Precipitation during La Niña Winters.

Notice all the acronyms end with an "O" for oscillation. These are all cycles of temperature trends for different oceans or regions of oceans. Oceans are where the lion's share of Earth's heat is stored. Most of Earth's heat comes from the Sun, while a fraction comes from the Earth's molten iron core via vulcanism...see deep ocean vents for example.

The Sun has cycles too, though I'd wager we haven't discovered most of these yet. The most familiar cycle is the Sunspot Cycle. It's the first one we noticed. The earliest surviving record of sunspot observation dates from 364BC , based on comments by Chinese astronomer Gan De in a star catalog. The first clear mention of a sunspot in Western literature, around 300 BC, was by Theophrastus, a student of Plato and Aristotle.

I was 50 years old when I saw my first sun spot. I was on The New Seeker a "party boat", off the beach at Pacifica fishing for salmon. The marine layer was just the right thickness to reveal the disc of the Sun which was sporting a huge sunspot several times the size of the Earth.

Solar observers say the Sun is being very quiet, just another monkey wrench in the forecaster's bailiwick to complicate their job.

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