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July 16, 2009 July 16, 2009 July 16, 2009 July 16, 2009
Urban Heat Island Part 2
The last Ticker introduced the urban heat island in a broader concept and demonstrated
that one has been measured for Oklahoma City. It is time to bring the younger sibling of
the Mesonet back for more insight into this feature: the Oklahoma City Micronet
(OKCNET).
One of the first features we noticed with OKCNET was the presence of an urban heat
island nearly everyday (and all day as well). The dense network of stations was able to
detect the strong differences in air temperature between the urban core and the surrounding
rural areas. The temperature measurements collected by OKCNET also
revealed that the more suburban areas of the Oklahoma City metropolitan area also are
warmer than the rural areas but not as warm as the location near the core of Oklahoma
City. Here is a nice example from when it wasn?t nearly that hot (actually quite cold) following
a clear night with light winds:
http://res.mesonet.org/~jbasara/Ticker/July_15_2009_Ticker/OKCNET_TAIR_Wind_UHI_121108.jpg
Notice the ?bullseye? in air temperature directly over the central business district of
Oklahoma City with air temperature decreasing through the suburban to the rural areas.
Of course, it is rare to find a calm day in Oklahoma, and typically we see the warmer air
of the central business district ?transported? downwind like the following from last
August:
http://res.mesonet.org/~jbasara/Ticker/July_15_2009_Ticker/OKCNET_TAIR_Wind_UHI_080508.jpg
The structure of this feature represents more of a plume than an island.
However, once again where you live is important regarding the temperature you may
experience.
Now, true urban observations such as those from the Oklahoma City Micronet are
actually quite rare as most weather stations are typically deployed deployed on the
outskirts of cities. Even so, check out the following image which shows the warmest
minimum temperatures across the Oklahoma Mesonet this morning:
http://res.mesonet.org/~jbasara/Ticker/July_15_2009_Ticker/Mesonet_Minimum_Temp_071509.jpg
The three Oklahoma City sites were not the warmest in the state during the day, but
were at night. Also note that the warmest of all was the site located 7 miles downwind
of the central business district of Oklahoma City. I?ve noticed that this has been a
regular occurrence especially lately during this heatwave. The urban heat island is almost certainlly the
contributing factor to the warmer temperatures at night at these Mesonet sites.
So, in case you are thinking that because you don?t live in OKC that an urban heat island
doesn?t exist, think again. Wherever, manmade structure are clustered together there
will be an impact on the temperature. Thus, while the impacts might not be as larger as
Oklahoma City (or larger yet in Dallas, Houston, etc.), they are likely to be occurring
perhaps without anyone even realizing it.
The impact of the urban heat island also leads to more questions such as: so how does the
urban heat island interact with heat waves like what we?ve been experiencing? Sounds like
another future Ticker (stay tuned). In the meantime, I?ve added to our collection of links to follow.
http://www.mesonet.org/
http://okc.mesonet.org/
http://twitter.com/ocsticker
http://www.facebook.com/group.php?gid=80762543949
http://www.facebook.com/group.php?gid=2204800994
Ticker Author: Jeff Basara
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