Agronomy 405/505
Spring 2009
Problem Set 2
Due Tuesday, January 27, 2009
Assigned January 20, 2009
1. Vist the Iowa Environmental Mesonet (http://mesonet.agron.iastate.edu) and
follow the following links to see the meteorological data collected at ISU meteorology instructor David Flory’s house: “Other” under “IEM Data Networks;” and then
“Mesonet Northeast Ames.” Look at the data for January 16 (when we finally got out
of the deep freeze) and January 20 (Inauguration Day), 2009.
You can download the raw data by clicking on “View raw data file.” The columns are
in this order: month; day; year; hour; minute; current outside air temperature (◦ F);
highest recorded air temperature so far that day (◦ F); lowest recorded air temperature
so far that day (◦ F); outside relative humidty (%); wind speed (mph); wind direction
(degrees); peak wind gust (mph); time of peak wind gust; air pressure (inches, adjusted
to sea level); precipitation so far that day (inches); precipitation so far that month
(inches); precipitation so far that season (inches); inside air temperature (◦ F); and
inside relative humidity (%). Note that each day’s high and low temperature is also
listed on the web page above the figures, so there is no need to search through the raw
data.
Compare the air temperature data for both days with the empirical model defined
by Equations (2.2) and (2.3) in Campbell and Norman (the class notes contain some
minor corrections) using the example m-file flory_example.m and the data file flory_
01162009.dat.
(a) Produce a figure with two curves for January 16: the output of the empirical
model defined by (2.2) and (2.3); and the actual data.
(b) Does the model match the data for January 16? Explain.
(c) Produce a figure with two curves for January 20: the output of the empirical
model defined by (2.2) and (2.3); and the actual data. Remove from your data
file (using a text editor) any data that is recorded after midnight.
(d) Does the model match the data for January 20? Explain.
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2. Explain why ω = π/12 rad hour−1 in Campbell and Norman Equation (2.2).
3. 2.1 in Campbell and Norman. Use the m-file for Example 2.2 on the course website as
a guide.
4. 2.2 in Campbell and Norman. Is this a moist or dry soil?
5. 2.4 in Campbell and Norman. Use the data file provided on the course web site so
that you don’t have to enter all the data by hand. I’d like you to try to solve this
problem using MATLAB, but if you get stuck, try using another tool like a spreadsheet
application.
6. Read the Eos article “Where are the Hottest Spots on Earth?” on the course website.
Eos is a weekly periodical published by the American Geophysical Union (http://www.
agu.org), a professional association supporting the study of Earth and space science.
(a) What is the current world record air temperature (at the time that the article
was written), and where was it recorded?
(b) What does the acronym LST stand for?
(c) The MODIS sensor on NASA’s Aqua satellite discussed in this article consists of
several radiometers. A radiometer is an instrument that measures electromagnetic
radiation. We’ll learn later in this class about how all objects/surfaces emit radiation, and that this radiation is related to the temperature of the object/surface.
When an instrument measures the radiation emitted by an object/surface and we
interpret that measurement of radiation in terms of a geophysical quantity (in
this case temperature), this is called a remotely–sensed measurement. What is
an advantage of using remotely–sensed measurements of LST?
(d) What is a disadvantage of using remotely–sensed measurements of LST?
(e) According to MODIS, what is the hottest Earth LST, and where did it occur?
(f) How does vegetation influence LST? Explain.
(g) How does irrigation influence LST? Explain.
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