Saturday, May 21, 2011

Michigan combined temperatures

Michigan has 24 USHCN stations, ranging from Adrian to Stambaugh and it also has 6 GISS stations on the list.

The GISS stations include Detroit, which has four stations, of which that at Detroit/City Airport has the right co-ordinates, though it also has only data from 1948. Then there is Grand Rapids, which has three stations, of which the third has the right co-ordinates, and has data going back to about 1885.

Third on the list is Muskegon which has only one site, but also only data from 1948. The fourth site is in Flint which starts in 1949. Fifth is at Sault Ste Marie which has three stations, but the one logically to choose is the USA designation. That has data from 1880. And finally there is Marquette which also has a USA designation and data from 1880.

Looking at populations, the station at Champion is in the State Park, but a look through Google Earth shows that it is near some buildings.

Champion Van Riper state park station in Michigan

So I gave it a population of 20. Other than that the data acquisition was straightforward. Looking at the results:

The influence of the change in the number of stations used is clear with the step in the 1940’s. And going from the homogenized to the TOBS temperature data:

The temperature rise has been around 1 degree every century, the USHCN homogenized data would suggest that it is actually twice that.

Michigan is in two pieces, and is surrounded by considerable volumes of water, which may have an influence on both climate and how it changes. It runs from roughly 82.5 deg W to 90.5 deg W, and from 41.67 deg N to 48.25 deg N. The geographic center is 85 deg W, 45 deg N. The latitude mean for the USHCN stations is 43.9 deg N, and that of the GISS stations is 44.1 deg N, both therefore a bit South of the mean. The mean elevation of the state is 274 m, ranging from 174 m to 603 m. The mean USHCN elevation is 264 m, and that of the GISS stations is 195.5 m.

Looking at how this affects the temperatures:

There is the clear correlation with latitude, and no correlation with longitude.

Even though there are a number of places with similar elevations, there is a clear correlation with elevation.

And when one uses the average of the past five years temperatures against population, there is a clear correlation here too.

And finally, to explain the difference between the temperature record and the USHCN homogenized values for temperatures in the state:

Interesting how many of these particular plots have that little kick at the end.


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