Wednesday, 10 November 2010
The PDO and it's influence on North American Temperatures, two examples.
Information on the PDO can be found here. Generally speaking, a positive PDO index indicates warmer than normal SSTs (sea surface temperatures) surrounding a cool pool in the NW Pacific Ocean. A negative PDO index indicates cooler than normal SSTs surrounding a warm pool in the NW Pacific. A positive PDO will have a predominance of El Ninos. A negative PDO will have a predominance of La Ninas.
Since Enviroment Canada does not have handy online graphing tools, I will use the states of Washington and Alaska as my two examples for the PDO effects on west coast temperatures. One can assume the province of BC will be very similar.
First the graphic of the PDO index:
Note the time periods:
Negative post 1945 to late 1970's
Positve from the late 1970s to about 2007 where the PDO switched negative once more.
Currently PDO is strongly negative as can be seen by the current SST graphic.
Now Washington state yearly temperatures from here.
While a lot more variable (naturally) than the PDO index, if one notes the transition points especially of the green line, they correspond to the PDO index.
Secondly, Alaska (note these are Jan-Oct anomalies, I couldn't find full year graphics..but the point is made):
Again using the black line as a reference, again a strong correspondance to the PDO index. With the strongly negative PDO and La Nina, Alaska is going to have its coldest period its had in quite a while.