Microclimates Flashcards
what holds more heat:
rural or urban
urban
why are urban cities hotter
because they lack vegetation that would cool them down
what is UHI
urban heat island
strategies to reduce the urban heat island effect
- vegetation
how do urban microclimates differ from those of nearby non-urban areas
they regularly reach temps as much as 5 degrees warmer
what produces the UHI
the physical characteristics of urbanized regions
how is heating increased in cities
by modified urban surfaces
1. asphalt
2. glass
2. pollution
3. human economic activities
most major cities produce a _____
dust dome
dust dome is
airborne pollution trapped by certain characteristics of the UHI
UHI is largely a ____ phenomenon
night time
true or false
a city cools down a night
FALSE
why don’t cities cool down at night
because the radiation has no where to escape above it
3 causes of UHI that are based on the energy budget
- increased absorption of short-wave radiation
- increased longwave radiation from sky
- decreased longwave radiation loss
what reduces the total long waves
much of the L waves emitted is absorbed and re-emitted to the surface
a canyon floor causes radiation to
be absorbed and reflected less
why does UHI cause the loss of less than normal amounts of longwave radiation
because there is more around that keeps the radiation from escaping (buildings, clouds, dust dome)
what allows a city to cool down at night
the loss of longwave radiation
the canyon floor idea is based on the fact that
there are not a lot of avenues available for the radiation to reach the sky and is instead absorbed more
what are the 7 causes of the UHI
- increased absorption of shortwave radiation
- increased long-wave radiation from sky
- decreased long-wave radiation loss
- anthropogenic heat source
- decreased evapotranspiration
- increased heat storge
- decreased total turbulent heat transport
what features reflect increased shorwave absortion
canyon gemotery - increased surface area and multiple reflection
what features reflect increased long-wave raidation from sky
air pollution - greater absorption and re-emission
what features reflect decreased long wave radiation loss
canyon geometry - reductions of sky view factor
what features reflect anthropogenic heat source
building and traffic heat loss
what features reflect decreased evapotranspiration
construction materials - increased impermeability and no water to carry away heat
what features reflect increased heat storage
construction materials - increased thermal admittance
what features reflect the decreased total turbulent heat transport
canyon geometry - reduction of wind speed (wind cannot carry heat away because it is being blocked)
