Agronomy 405/505
Spring 2013
Problem Set 2
Due Tuesday, January 29, 2013.
Assigned January 22, 2013. Updated January 23, 2013.
Updated January 25, 2013 (Question 2).
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 July 22, 2012, and January 2, 2013.
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 is shown in Table 1.
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. 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 July 22: 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 july21.dat, july22.dat, and july23.dat from
the course syllabus.
(b) Does the model match the data? Explain.
(c) Produce a figure with two curves for January 2: the output of the empirical model
defined by (2.2) and (2.3); and the actual data. Use diurnal_example.m as a
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Table 1: First records of data for July 22 and January 2 from IEM Central Command.
114 2012 204 7 25.28 77.5 75.5 1.150 135.9 1016 0.000
114 2013 2 2 -12.97 8.66 74.7 2.225 179.7 1020 0.000
template and create your own data files. 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).
(d) Does the model match the data for January 2? Explain.
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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