AGRON 405/505 Spring 2015
Problem Set 2
Due Tuesday, January 27, 2015.
Assigned January 20, 2015.
1. How well can we estimate diurnal temperature change using the empirical model discussed
in class? Vist the Iowa Environmental Mesonet (http://mesonet.agron.iastate.edu) and
follow the following links to see the meteorological data collected on the roof of Agronomy
Hall: “Other” under “IEM Data Networks;” and then “IEM Central Command.” Look at
the data for January 16 and January 17, 2015 (last Friday and Saturday).
You can download the raw data by clicking on “View raw data file.” Select All, Copy, and
Paste this data into a text file using a text editor (like TextEdit for Mac OS or WordPad
for Windows, or even Microsoft Word). The first record for the January 16 data is shown in
Table 1. If using Word, be sure to save it as a text file, preferably with extension .txt.
We can guess at what the columns hold. The 114 is likely the identifier for the version of
the computer program that was used to collect this data. (This is important because as you
add instruments, the program will change and it is important to keep track of what program
generated the data so you can identify the data.) Then comes the year, the day of year, and
the time of day in the format “hhmm” where hh = hour and mm = minute. (Note that for
some reason the data record for January 16 begins at 1:01am, not 12:00am.) I don’t know
what the next column is. (Can you figure it out?) Next the air temperature (◦ F), the relative
humidity (%), the wind speed (m s−1 ), the wind direction in degrees, the air pressure (mb),
and I am guessing the precipitation.
Compare the air temperature data with the empirical model defined by Equations (2.2) and
(2.3) in Campbell and Norman (the class notes contain some minor corrections).
(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. Use diurnal_example.m (and my
function timeconvert.m, which must be in the same directory as diurnal_example.m)
and the data files jan15.txt, jan16.txt, and jan17.txt from the course syllabus.
(b) Does the model match the data? Explain.
(c) Produce a figure with two curves for January 17 (the next day): the output of the
empirical model defined by (2.2) and (2.3); and the actual data. Use diurnal_example.m
as a template. You will need to create another data file. Make sure to delete: records
that are not needed (any data at the beginning or end of the IEM data file that was
observed either before or after the day in question); empty rows; and any row that
has something obviously wrong with it (MATLAB expects each row to have the same
number of columns, else you’ll get an error message).
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Table 1: First record of January 16 data from IEM Central Command.
114
2015
16
101
-1.362
29.55
90.9
1.737
215.3
1021
0.000
(d) Does the model match the data for January 17? Explain.
(e) Do you think the model defined by (2.2) and (2.3) is a good model? Explain.
(f) Name one thing that could be changed to make this model better.
2. The dominant term of the dimensionless fluctuation (2.2) in Campbell and Norman is
− sin (ωt + 0.9)
(1)
but the sinusoid in (2.4) of Campbell and Norman is written
sin [ω (t − 8)]
(2)
when z = 0. Rewrite (1) using the form of (2), i.e. find l if (1) is written + sin [ω (t − l)] and
ω = π/12 rad hour−1 . Does the value of l make sense? Why or why not?
3. 2.1 in Campbell and Norman. Look at m–files for Example 2.1 and 2.2 on the course syllabus
for guidance.
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 P2_4data.dat provided on the course syllabus
so that you don’t have to enter all the data by hand. Look at the example m–file interest.m
for help. 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 “Record-breaking Early Flowering in the Eastern United States”
with doi:10.1371/journal.pone.0053788.
(a) What is phenology?
(b) The authors take advantage of phenological observations made by what two famous
Americans?
(c) Why is there cause for concern about changes in the timing of phenology? Give at least
one reason.
(d) What is the average rate of change in date of flowering for every 1◦ C rise in temperature
in Massachusettes? In Wisconsin?
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