Temperatures in the Flat Middle of the USA

Last week I noted the curious drop in temperature along the Eastern Seaboard in the period from around 1950 to 1965. The question then arises as to whether there are other pieces of information in the data that I have accumulated, and so, out of curiosity, today I will look at the strip of states in the middle of the country and compare their average temperature with that of the East Coast. (Checking to see if my memory that there wasn't quite the same drop is, in fact, true).

I am trying to stay away from mountains in this strip, so I will pick Minnesota, Wisconsin, Michigan, Iowa, Illinois, Indiana, Kansas, Missouri, Oklahoma, Arkansas, Texas, Louisiana, Mississippi, and Alabama. And, while there are some hills in the selection, just for simple characterization I am going to call these the “Flat Mid States.”

Interestingly all these months since I first looked at Arkansas, there is still a problem downloading the data for Rohwer from the USHCN, so I used the GISS values instead (recognizing that they are a little manipulated, but since I am averaging over 15 stations, reckoning that the “adjustment” won’t make that much difference.)

Looking at the average plot just averaging the state average values, calculated in earlier posts, one gets, for the homogenized data:

Averaged temperature in the Mid States using state average homogenized temperatures

When one uses the TOBS data, rather than the homogenized values, then the curve changes to

Averaged temperature in the Mid States using state average TOBS temperatures

If I weigh the results by the stations in the state (there are a total of 405 stations in this series), then the result, using TOBS data becomes:

Averaged temperature in the Mid States using state average TOBS temperatures, weighted by number of stations

The effective result of the weighting in the above plot is just to average all the station data. When, however, the area of the states is considered, bearing in mind that apart from Texas they are all much the same size, then the result becomes:

Averaged temperature in the Mid States using state average TOBS temperatures, weighted by state area.

It should be noted that the trend over the range of data is sensibly zero, i.e. there has been no temperature increase on average for these states, over the past 110 years.

The drop in temperature, so clear in the data for the Atlantic States is not as prolonged here, falling from 57.9 deg F in 1954 to 55.1 deg in 1960. Comparing the two plots:

Average temperature in the Flat Mid states (upper green) , relative to those of the Atlantic Shore states (lower red), averaging states weighted by area.

Note that there is a definite rise in temperature along the sea siding states. Also the larger size of Texas tends to give a larger weight to the south here, and thus the overall higher average.

Looking at the individual trends for each state in this set, I have again divided it into two sets to make it easier to distinguish the individual lines.

Average temperatures for the Northern set of states in the Flat Mid region

Note that Wisconsin and Michigan virtually overlap.

Average temperatures for the Southern set of states in the Flat Mid region
Here it is Arkansas and Oklahoma that are almost superimposed.

I will go on to look at other regions and compare them to see how temperature averages differ around the country, but will leave you with the usual comparison.

Difference between the average value for the USHCN homogenized values after the original TOBS values have been subtracted.