Grand Canyon Microclimatology_ Helicopter Data Tour
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School
Arizona State University *
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Course
112
Subject
Geography
Date
Apr 3, 2024
Type
Pages
3
Uploaded by elcorrido
Fast travel to 36.1795 , -111.8014. Take a helicopter ride west to 36.0359, -111.8373. Along the
path, observe the summer temperature variations along the bottom of the canyon. What major
observations can you see, and why do you think the temperature variability looks the way it
does?
The bottom of the canyon (the river) is much warmer than the surrounding cliffs and platforms -
this is likely due the significant tree canopy that exists at the bottom of the canyon here.
Correct!
The bottom of the canyon (the river) is much cooler than the surrounding cliffs and platforms -
this is likely due to the evaporative cooling and the cool temperature of the river itself.
The bottom of the canyon (the river) is much cooler than the surrounding cliffs and platforms -
this is likely due to ice forming along the top of the river.
The bottom of the canyon (the river) is much warmer than the surrounding cliffs and platforms -
this is likely due to the evaporative cooling and the cool temperature of the river itself.
Nice work!
The same amount of solar radiation “hits” the Colorado River and surrounding riparian
(riverside) vegetation as the nearby desert slopes. What happens next to this solar radiation is
very different.
In and along the river, the solar radiation is used to evaporate some water of the Colorado River
and is also used for photosynthesis by the riparian plants. The net effect is a lot of cooling from
evaporation and evapotranspiration by plants.
On the desert slopes with only a few plants and lots of bare ground, the solar radiation heats up
the surface. This solar radiation is then re-emitted by the earth in the form of sensible heat flux
(heat that you can feel) and other forms of long-wave radiation.
Question 2
You hopefully have made some good observations on the orientation of slopes and how the
shape of the topography influences temperature. Sometimes though, seasonal changes and
topography can make for some interesting observations.
Fast travel to 36.3408 , -112.1180 and take a helicopter tour along a shallow valley along the
North Rim towards 36.4454, -112.1410. Toggle between winter and summer temperatures as
you fly across the North Rim
What summer and winter temperature observations can you make along this shallow valley?
The valley is typically warmer in the summer but cooler in the winter compared to surrounding
hills
The valley is typically cooler for both seasons compared to surrounding hills
The valley is typically warmer for both seasons compared to surrounding hills
The valley is typically cooler in the summer but warmer in the winter compared to surrounding
hills
You should have seen something like the image below.
northrimvalley.png
To explain the winter temperature, cold air is dense and it slides down into low spots like shallow
river valleys. This happens when there is not a lot of wind. You can see in the adjacent image
what cold air drainage looks like in the game; shallow creeks on the Kaibab Plateau of the North
Rim accumulate cold air at night and surfaces cool down.
Question 3
The data for the winter and summer temperature layers come from a Landsat satellite image
taken during a specific time of day.
Fast travel to 36.0230, -112.0635 and toggle between winter and summer as you take a
helicopter ride to 35.9991, -111.9302. Based on the location of the sun throughout the day (as it
travels from east to west across the canyon), what time of day best explains the temperature
differences you see along the cliffs of the South Rim?
Night (2am)
Night (11pm)
Correct
Morning (10am)
Afternoon (4pm)
You should have seen a fairly stark difference between the west and east facing slopes. The
east facing slopes were warmer, as the sun still has not had the chance to warm the western
slopes yet.
You can see this example of warm eastern cliff faces vs cooler western cliff faces below.
a1_2.JPG
Question 4
Change the data layer to show NDVI (vegetation).
The NDVI vegetation layer is displaying information called Normalized Difference Vegetation
Index (NDVI) quantifies vegetation by measuring the difference between near-infrared (which
vegetation strongly reflects) and red light (which vegetation absorbs). On land, NDVI typically
ranges from 0 to 1. When you are playing the video game, and you click on the NDVI to show
biomass, this scale will be useful in interpreting the plants that are growing:
ndvi.jpg
The lower limit of trees in mid-latitude settings like mountainous terrain of the western USA is
typically controlled by a combination of the amount of precipitation, the seasonality of the
precipitation, and how hot it gets in the summer. Also important is aspect (the direction a slope
faces).
Fast travel to the South Rim (36.0442, -112.0586). Then, take a helicopter ride across the
canyon to the North Rim (36.2274, -112.0296). Along the way, observe the differences in the
location of the NDVI layer, with respect to the depth of green vegetation found along the ride.
How do north facing slopes compare to south facing slopes regarding the treeline into the
canyon?
The main difference is found at the bottom of the canyon, with both north and south facing
slopes along the river having the highest NDVI values
There is no real difference between north and south facing slopes with respect to treelines into
the canyon
Correct!
North facing slopes (like those found along the South Rim) have treelines deeper into the
canyon compared to south facing slopes (like those along the North Rim)
South facing slopes (like those found along the North Rim) have treelines deeper into the
canyon compared to north facing slopes (like those along the South Rim)
The diagram shows how aspect influences the elevation of lower treeline.
grca-life-zones.jpg
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