Tuesday, June 30, 2015

Pattern Correlations with Temperature

This is a quick post to show a series of figures that I created recently while examining the connection between Bering Sea pressure anomalies and temperatures in Fairbanks.  Each of the maps below shows the correlation between monthly-mean sea-level pressure (left) or 500 mb height (right) with the monthly-mean temperature in Fairbanks.  It's interesting to see the seasonal progression of pressure patterns that tend to favor either unusual warmth or unusual coolness in Fairbanks.

Here are a few features that jump out at me; perhaps readers would like to suggest others.

- Upper-level heights over northwest Canada are strongly connected to Fairbanks temperatures in most months, but in summer the area of highest positive correlation shrinks and doesn't extend much beyond the borders of Alaska.

- In June the semi-permanent connection between Bering Sea low pressure and Fairbanks warmth (or high pressure and coolness) all but vanishes.  However, it starts to return already in July.

- There is an interesting difference between December and January, with December temperatures being most strongly connected to Bering Sea conditions, but with January temperatures being more heavily influenced by flow features to the east.


  1. I find it fascinating how the Bering Low starts in the Bering Sea during winter and slowly migrates in a counter-clockwise motion around Alaska through June. It disappears for a moment then starts to move back for the winter. Could the disappearance be attributed to changing winds?

    The Canadian High starts in the Yukon during winter, slowly migrates counter-clockwise around Alaska till June, then reverses course to go back to the Yukon. It does appear to weaken a little also in June.

    I'm also struck on how strong the correlations are for just around Alaska. I'm even more struck by the lack of correlations elsewhere in the hemisphere. I would expect there to be more random correlations scattered around; where are the blue and red pokadots?

  2. Eric, thanks for the comments. To me, the weakening of the signals in June indicates that Fairbanks temperature anomalies can occur with a wider variety of pressure patterns than in other months; the temperature is less tied to a canonical flow pattern. Yes, this must be a consequence of changing wind (jet stream) patterns and thus also of seasonal temperature changes (and particularly land-sea temperature contrast, I suspect). But I don't have any firm explanation of the seasonal changes.

    Part of the reason for lack of random correlations around the hemisphere is that I used a broader contour interval of -0.2 to +0.2 in the middle, because I wanted to de-emphasize random and spurious correlations. Also, I am sure if I correlated Fairbanks MSLP/heights with MSLP/heights elsewhere, then various teleconnections would show up on the map. But yes, it is a little surprising that not more hemispheric-scale connections are evident.