Geography 3015 – Lab Exercise 3 – October 13, 2005
Microclimatological Data Analysis – Part A
In this lab exercise, you will gain experience analyzing standard microclimatological
datasets, using spreadsheet applications. There are two parts to this lab. In Part A (worth
7%), you will examine an existing dataset (Lethbridge Grassland, Ameriflux, Dr. L.B.
Flanagan), to acquire experience in (i) producing time series and scatterplots of
microclimatological variables and (ii) interpreting this data. (N.B.: We’ll be coming back
to this dataset during the NEE/carbon balance lab, and comparing it with an Ontario
peatland site). Part B (worth 8%), next week, involves microclimatological data
collection from distinct slope and aspect positions in the Lethbridge coulees (Oct 13-20,
2005), and the analysis of the resulting dataset. Be sure to take note of the synoptic
conditions each day during the next week and make yourself familiar with the study site.
PART A:
1. Using Dr. Larry Flanagan’s Lethbridge 2004 grassland data in “GEOG 3015 LAB 3
FLUX DATA.xls,” produce a complete energy balance plot (time-series) for (i) April 1 to
April 5, (ii) May 1 to May 5, (iii) June 1 to June 5, (iv) July 1 to July 5, (v) August 1 to
August 5 and (vi) September 1 to September 5. Be sure to label your diagrams properly,
including titles and units. (6 marks)
2. Based on the six graphs you have produced, describe the seasonal differences in each
component of the energy balance equation during the growing season, and explain the
reasons for any differences noted. (Plotting the entire time series might help you notice
overall trends, though you won’t be able to resolve diurnal patterns clearly). (9 marks)
3. Describe and explain the diurnal and seasonal patterns in the Bowen Ratio.
Qualitatively, briefly describe the effects of precipitation, cloudiness and vapour pressure
deficit on . (5 marks)
4. How does Q*, calculated from the energy balance diagram above, compare with
measured net radiation? Is your result expected? Why or why not? (3 marks)
5. On Friday, April 2, what is the soil temperature wave amplitude for depths of 2, 4, 8
and 16 cm? (2 marks)
6. What is the lag time between peak soil temperatures at 2cm and 16 cm depths? Using
this information, estimate the thermal diffusivity of this soil, Hs. This soil was
moderately moist on Friday, April 2, with a saturation ratio of about 0.67 (volumetric
water content, , of 0.29). Generally speaking, what would happen to the thermal
diffusivity of the soil if it were very dry? What would happen if it were saturated?
Explain why. (7 marks)
7. Is this soil dominated by sand, clay or organic fractions? Explain your answer. (3
marks)
PART B:
We have collected microclimatological data during the past week in the University of
Lethbridge coulees. In this part of the assignment, we will use comparative techniques
(time series plots and scatterplots) to compare and contrast temperature and humidity
conditions at a north facing site, south-facing site and an open, flat site, in October, 2005.
The data in question run from October 14 to October 20, and are found in the file entitled
“GEOG 3015 LAB 3 PART B.xls”
1. Compare 10 cm vs. 1m air temperatures at (a) the south-facing site, (b) the northfacing site and (c) the open site. If one of the sites seems to have greater differences
between the 0.1 m and 1m heights, explain the reason(s) for this. Do you detect any
diurnal patterns in temperature differences between the two heights at any of the sites? (8
marks)
2. Compare 10cm air temperatures at the N-facing and S-facing sites. Which site has the
highest temperatures during (i) the day and (ii) the night? Which site has the greatest
diurnal variation and why? Compare the 1m air temperatures at the N-facing and Sfacing sites. Are the patterns the same as for the 10cm values? Explain any patterns you
notice, based on your notes on the site characteristics (8 marks)
3. Which site has higher soil moisture. Why? (2 marks)
4. Is there a relationship between solar radiation intensity and the temperature difference
between the three sites at 10cm? at 1m? Explain your observations. (6 marks)
5. How do (a) dewpoints (or, even better absolute humidities) and (b) relative humidity
vary (i) between 10cm and 1m at the three sites and (ii) between sites ? (6 marks)
6. Open answer question: Explain how the synoptic conditions you recorded over the
past week affected the diurnal temperature patterns observed at the three sites. (10
marks)