July Regional Temperature Update


My 2011 experiment of comparing the Urban Heat Island (UHI) in my region is proceeding and the very interesting summer results are starting to show up.  The results are pretty clear that urban areas do impact the anomaly data for an area and using such contaminated data will give a false warming bias that is not being properly accounted for in the temperature records.  Feel free to review the earlier articles on this.

The two temperature records continue to show that they are in fact comparable for weather.  Warming and cooling fronts reach both places nearly simultaneously.  In this manner weather is removed as a variable for the two locations leaving only the warming and cooling that take place each day.

The Inconvenient Skeptic

(Black) Boise Daily, (Green) McCall Daily average temperature.

These average daily temperatures are what are used by the station method to determine the temperature anomaly that is eventually used to provide the temperature of the Earth.   Each day’s average temperature is compared to the average temperature to determine the daily temperature anomaly.  These are then averaged for the year.

The Inconvenient Skeptic

(Fill) Daily temperature anomaly for Boise.

The Inconvenient Skeptic

(Fill) Daily temperature anomaly for McCall.

What this shows is that Boise is experiencing a summer that appears to be warmer than average.  That is saying that it has a positive temperature anomaly.  McCall is showing that the last part of the year at least has about average temperatures.  This fails to accurately describe what is going on in either place which is one reason why the station method has problems.

Far more useful is the anomaly for the maximum and minimum temperatures.  This is where the issue of the UHI is easiest to see and during the summer it is very clear that the issue is real.  That is because urban areas are slow to warm down during the night and retain their heat longer than rural areas.  This results in higher than average low averages.  The more sunlight an area gets during the day the stronger the effect is.  Summer is the ideal testing ground for this issue.

(Red Fill) Max temp anomaly. (Blue Fill) Minimum temp anomaly.

(Red Fill) Max temp anomaly. (Blue Fill) Minimum temp anomaly.

In the Boise urban area the low temperatures during the past month have all been well above average while the rural McCall area shows no such behavior.  The weather patterns are the same, but the night time temperatures are not.   The same is not true of the day time high temperatures.   Boise has had higher day time temperatures than McCall, but they are not all above average.

Boise over the last two months has experienced a low temperature anomaly that is +2.1 °C.  The average high anomaly for that same period of time is a -0.8 °C.  That is the signature of the UHI.  That this is the same description that some places use to show how global warming is impacting the Earth, they ignore the fact that urban data will create the same temperature signature.

Posted in Anomaly and Climate and Problem with the Station Method by inconvenientskeptic on August 1st, 2011 at 9:10 am.

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