IEM Daily Feature
Thursday, 19 July 2012
Thursday, 19 July 2012
Ames v Des Moines
Posted: 19 Jul 2012 05:46 AM
While the thermometer hit 103 degrees at the official observation site
in Des Moines (the airport ASOS), it was 6 degrees cooler a handful of
miles north in Ames as it only reported a high temperature of 97. The
featured chart shows the daily maximum temperature from these two sites
for July along with the maximum reported dew point for the day. Why is
Des Moines always warmer than Ames and Ames not having reached 100
degrees yet? Location is everything. The Des Moines airport is
surrounded by an urban landscape on most sides, while the Ames site has
mostly corn and soybean fields nearby. Agricultural areas promote
higher humidities due to crop transpiration, while urban areas are
comparatively drier. This difference is clear from the difference in
maximum dew points. The micro-climate around the Ames site is much
more humid, which means it takes more energy to heat the air. So for
the same incoming radiation, it will take more energy to raise the
temperature one degree at Ames versus Des Moines. There is also a
general urban heat island effect that happens moreso in Des Moines than
Ames, due to intensity of the urban landscape promoting warmer
overnight temperatures (all of the buildings and concrete hold heat
better than vegetation and topsoil).
Voting:
Good = 94
Bad = 16
Tags: heatisland
Voting:
Good = 94
Bad = 16
Tags: heatisland