Geoscience Reference
In-Depth Information
D i s c o v e r…
DEATH VALLEY
Do you feel physically comfortable right now? Regardless
of how you feel right now, it is safe to say that it would
feel decidedly uncomfortable if you were in Death Valley,
California, in the summer. Located in the Mojave Desert,
Death Valley lies in the rain shadow of the Sierra Nevada and
has the lowest elevation in the United States at 86 m (282 ft)
below sea level. It is located only 136 km (84.6 mi) east/
southeast of Mount Whitney, which has the highest elevation
in the contiguous 48 states at 4421 m (14,505 ft) above sea
level. Given this large elevation difference over such short
geographical space, the air temperature warms dramatically
as it descends from the Sierra peaks to the floor of the val-
ley. As a result, average temperature exceeds 27
o
C (80
o
F)
eight months of the year and 38
o
C (100
o
F) for five. In fact,
Death Valley holds the official record for highest reported
temperature on Earth at 56.7
o
C (134
o
F) in 1913. As you can
imagine, the relative humidity is low, often at or around 35%.
This combination of high air temperature and low humid-
ity frequently makes conditions extreme. In July 1966, for
example, the air temperature was 119
o
F with 31% relative
humidity. With the heat index in mind from Chapter 5, this
combination of high air temperature and very low humidity
meant that it felt like 64
o
C (148
o
F) that day! No wonder the
place is called
Death Valley
.
Orographic Processes
Now that you have a fundamental understanding of orographic pro-
cesses, we can integrate all the concepts that have been discussed
to this point in the text in a simulated format. At this time, go to the
Geo Media Library
and select
Orographic Processes
. This
animation will give you an opportunity to interact with the flow of
air across a mountain range and the fluctuating humidity levels that
occur on its ascent on the windward side and descent on the lee-
ward side. The first part of the animation provides a review of the
orographic process that shows the basic patterns. The second part
is a simulation whereby you can interact with the orographic pro-
cess along a fictional mountain range by adjusting variables such
as temperature and specific humidity before an air mass begins its
ascent on the windward slope. You can also change the elevation of
the mountains to see how this factor influences adiabatic processes.
In this context, you will be presented with several scenarios that rep-
resent a minute fraction of the nearly infinite number of possibilities
in nature. As you interact with this simulation, notice how the level of
condensation changes as you adjust the variables. Also, pay atten-
tion to the changes that occur with respect to the various forms of
humidity on both the windward and leeward mountain slopes. After
you complete the animation and simulation, be sure to answer the
questions at the end to test your understanding of this process.
