View Full Version : AO

03-20-2008, 03:42 PM
Hey John,

So I know the Arctic Oscillation is a factor that determines whether the US will be cold or warm during the winters. And I know for a fact that when it is in its negative phase, arctic air is available to move south into the US, while regions near the pole experience warmer weather. I've been looking at the AO all winter on the CPC website and have noticed a couple things. In December, there were 2 main peaks in the AO, in January there was one big peak in the 2nd half , and in February there was also one big peak in the 2nd half. When u match up the AO with periods that we were either in the "Deep freeze" or experiencing slightly warmer weather...what I have noticed is that it gets cold when the AO is trending downward, EVEN if it is still quite positive, and the weather warms when the AO trends upward. Based on the observed AO, majority of this winter, it was in the positive phase. But, the winter has been dominated by the AO trending downward, while the periods when the AO was rising where very quick and sharp. Is this part of the reason why majority of the winter has been cold? And Is this all true? (what I have observed) ..or does the AO have to strictly be negative for the pattern to be cold?

Sorry for the long write up.

03-31-2008, 08:31 AM
I guess the first thing that needs to be said is that there are no ABSOLUTS when it comes to the atmosphere. Things do not act in a black and white fashion. So with that said, each swing of the AO is bound to have different results as there are other things going on in the atmosphere on a global and regional scale that will influence the weather for a particular area.

I can also say that not much is really known about the AO. So it's effects and mechanisms cannot be fully explained yet either.

Because of all of these uncertainties, I guess the answer is really yet to be able to be explained. However, I think I would really point out that there is a whole lot more going on to make our weather in the winter than just what the AO is doing.