Brooks Hurd has sent in this set of observations of temperature changes while driving in and out of various Californian UHI’s in his Passat. Maybe some other readers could send in other data, good project for the kids to keep them occupied for a while.
This was taken with the
built in exterior thermometer on our Passat. I do not claim that it is
highly accurate. It rounds to the degree F, which is still more accurate
than the thermometer. It is, however, consistent enough for the data which I
took to be meaningful.
I drove from where I live in San Luis Obispo north through downtown and onto
101 to Newark, California (east side of San Francisco Bay). I left one hour
before sunrise so there was no effect from the sun. Sunrise was about the
time that I drove into King City. You can clearly see the temperature rise.
After Gonzales I quit taking data because of solar effects.
The towns which are en route are separated from each other by truly
rural areas, thus there is a good rural baseline. These towns, except for
San Luis Obispo, are located in the Monterey Valley.
The two step changes are where I drove over a ridge. The first ridge was the
Cuesta Grade. The second was in the Monterey Valley, just south of King
I took data when the temperature changed since this was less distracting
than taking data at constant time or mileage intervals. This compresses the
x axis, but clearly shows the UHI.
I was amazed that even the very small towns had a visible UHI. The spike in
San Luis Obispo up to 45 F was real. The temperature stayed at 45 until I
climbed most of the way up “The Cuesta Grade.” San Luis Obispo is at 50-70m
elevation. The top of the grade is ~500m.
I found problems in certain places. For example, Santa Barbara does not
provide useful data since it is located on the Pacific. The ocean overwhelms
the UHI. US Midwestern cities (located on plains), and cities located in
broad valleys (like the Monterey Valley) should provide good data since they
are not effected by nearby oceans or lakes.
I like valleys or plains, since these areas have a local climate which is
relatively consistent in the area surrounding the town/city of interest.