Thursday, December 8, 2011

ONI and individual state temperatures

The influence that sea surface temperatures have on land temperatures and climate is an ongoing debate, and I mentioned this somewhat in my last post on this topic. However, in looking back over that post it was perhaps too general an approach to look at the impact of the El Niño events over the large scale of the West Coast, and thereon East. Given that effects were, as I showed, more regionalized and remembering that we are in a La Nina winter, I’ll just repeat the anticipated effect plot from Kumar, et al.

Impacts of a La Nina winter (after Kumar et al).

The disadvantage of using the regional average can be seen just in the US West Coast. At the upper end the season is cooler and wetter, while down in the south it is drier and warmer – the average might well be “no change.” So since we have the individual state temperatures for the period I looked at last time, I thought it might be interesting, before looking at other Oscillations, to just check how this event correlated on a more localized basis.

The ONI plot from 1950 (GGWeather )

It is logical to start on the West Coast, and given that the predicted impact this winter will be on the upper Northwest, the first comparison is with Washington State. For now I am going to use the homogenized data set, rather than the TOBS data, though I may come back later to look at how that changes things. (This is the fun of doing this without an agenda, we don’t need to have the data fit any pattern, so it is more informative to look at options).

The ONI plot overlain on a plot of Washington state temperatures.

It can be seen that while there was some correlation, in places, overall the agreement is not very good.

The other states that seem to be most impacted are the southern tier, that would include California, Arizona, and possibly New Mexico and Texas . From the regional comparison the Pacific SST effects seem to weaken somewhat once one gets over the Rockies, hence the caution as to how far we might expect the impact along the South Coast – so we shall see.

Turning first to California, recognize in the beginning that with the state being as long as it is, there are internal temperature variations along the state, Overlaying the ONI plot on the relevant part of the California temperature curve:

Relation of California temperatures to ONI temperature anomalies

My sense is that the correlation is a bit better, but still lacking. So let’s try the Arizona comparison:

Relation of Arizona temperatures to ONI temperature anomalies.

There does seem to be more of a correlation here, than with the earlier comparisons.

Moving on to New Mexico, and the same superimposition:

Relation of New Mexico temperatures to ONI

Well what correlation there was in the first states seems to be getting less here, lets try Texas.

Relation of Texas temperatures to ONI

Well, using that well known calibrated eyeball, it would appear that the correlation seems to get worse as one moves away from the Pacific.

Well this wasn’t totally what I was expecting, though I mentioned at the top that I suspected that the effect might not reach as far as New Mexico. so I think I will cogitate a little more on this before venturing an opinion. However it might be worth looking at relative precipitation levels, since this seems to be more the effect that is most obvious. (Though that also gets into cloud formation . . . . . . )