[AZ-Observing] NWS Article: Urban Heat Island Effect on Monsoon Storms

This is sort of on-topic for Arizona observers, who often claim that the
presence of Phoenix affects the number and intensity of summer storms=2E  =
The
Phoenix National Weather Service office Web site has a good summary of the=

local and surrounding effects of the heat island on the monsoon=2E

http://www=2Ewrh=2Enoaa=2Egov/psr/general/monsoon/MonsoonPMA=2Ephp


And here is my summary version:

- The heat island was first described in 1921, when the metropolitan area
bustled with 80,000 residents=2E

- Everybody knows that the Phoenix nighttime lows have increased (by 7F to=

13F since 1961), but the same dataset shows the daytime highs decreasing b=
y
0F to 4F=2E  They attribute it to the moderating effect of unnatural
vegetation=2E  The "surrounding rural area" weather station that was used =
for
comparison to Phoenix is in the town of Maricopa, which has been doing its=

best to create its own heat island in the past few years=2E

- The contour maps of Valley rainfall do not support any of the anecdotal
claims of "hot spots" for monsoon storms=2E  It simply increases with
elevation with a good correlation=2E

- And now the punch line: a plot of precipitation in Phoenix over 112 year=
s
shows no upward or downward trend in precipitation as the population has
increased=2E

Tom

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