Saturday, April 3, 2010

Maine Temperature information

This is a part of a continuing look at state temperatures, and, since time is a bit short today, and since this was written in Maine*, I thought I would look at the temperatures there, rather than doing California, which with over 50 stations will take a little longer. Maine also provides an interesting contrast to Nevada, having some of the coldest temperatures in the contiguous United States, rather than some of the hottest. The process is the same as that I started with, and so I will be comparing the dozen USHCN stations in Maine with the single station that GISS uses. I wandered around trying to check that Caribou was the valid GISS site, as Chiefio listed. Along the way I bumped into the US Climate Reference Network (USCRN).
When fully deployed, the USCRN will consist of approximately one hundred stations nationwide at locations selected to capture both the national and regional climate trends and variations for temperature and precipitation.
The reason that I question the GISS use of Caribou, is the same as that which gave me problems when looking at Nevada. The temperature data from the site does not go back to 1895, as the USHCN data does, but in this case only starts in 1948, making a true comparison over the period of record impossible.

So, again being curious, I looked for a listing of the USCRN stations, which turn out to be different from the one provided by Chiefio. There are two stations on this USCRN list for Maine, one at Limestone (20020920) and one at Old Town (20020913). And this gets even more confusing since the data for Old Town from GISS only run from 1949 to 1972, and that for Limestone doesn’t apparently exist (the town has 1,415 people in it.) Perhaps it is a new station that is being installed? Maybe I should find out what is going on? But the record hasn’t been good on folk getting a response from those responsible (see the Climategate e-mails). So, given the confusion, I think that I will just stick with the Caribou station for now, since it does, at least have a significant length of time over which there is a record, that can be compared with the USHCN data.

However, by using this station I do invalidate one of the hypotheses that has been evolving from data from the last five states. For this is the first state where the GISS station temperature is lower than that of the average of the USHCN stations. Plotting the difference between the two, this really doesn’t appear to have changed over the time interval where there are records for both:

In Maine there has been a steady increase in state temperature over the past 114 years:

Now I had a second hypothesis that I was going to test, and this was that the influence of the sea would be evident in a warmer temperature near the coast, which dissipated as the stations moved west, and both away from the coast and higher. Well that one was wrong, at least in regard to it becoming cooler as the stations were further west and higher:

However there is a caveat to this result, in that the coast of Maine runs at an angle of about 45 deg along the bottom of the state, so it might be that we need to filter out the effects of latitude and altitude before having a closer look. Also, as I will note again later, there are only a limited number of stations in the state and two of them are sensibly on the coast.

The linear correlation with Latitude that has been detected for all the states so far, has persisted:

As has the linear inverse temperature correlation with Elevation above the sea, even though, in this case, the heights are not that great:

The change in standard deviation over time follows the pattern that we have seen in many of the states, starting out rising, and then, as automated temperature recording was introduced, reducing.

And so I now adjust the data by adjusting each station data to the latitude for the Center of the State, given as 45.250556, -45.250556.

Then I tried adjusting the data to the value if the station was located at the average height above sea level for the state of Maine, which is 600ft. And discover that this doesn’t work for all stations, since those that are below 100ft above the ocean tend to be dramatically overcorrected.

This comes back to the point that there are only a few stations in the state, and that there are only two that are that close to sea level, and we don’t have enough data at this time to draw a conclusion. Which means finding a state with more stations at the coast. . . . .

In the meantime to round out the usual set with a variation, here is the mid-state average temperature (i.e. adjusting each station for latitude as though it were at mid-state, and then taking the average – without Caribou – though it made very little difference). (To do this I subtract the constant term from each temperature based on the temp v latitude graph, then I multiply by the latitude of the center of the state, divide by the latitude of the station, then add the constant term back in).

And then to look at the effect of population, though again using the temperatures adjusted for latitude:

And we can still see that stronger sensitivity to population at small town sizes, that has been consistent across the states examined to date – but then they have all had relatively small population sizes.

* A series of problems that began with problems in getting onto the internet at the hotel, through having to change the router on our system when we got home, ends up with this also being completed on a new computer a week after the vast majority of the post was first written, sigh!


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