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Solar Radiation
Laboratory 5
Forest Ecology - FOR 3213 Purpose: to learn how to measure solar radiation and how the amount of light energy varies under field conditions.Methods: You will be provided with Ozalid paper light meters to measure total solar energy received under full light and shaded conditions in the field. The papers should be exposed for a full light period, developed with ammonium hydroxide and read for the number of pages bleached. The papers are coated with a light sensitive compound which is bleached by light. The papers are stacked in a book and exposed to the light. Ammonia vapor will develop the unbleached papers leaving the bleached part white. The number of stacked pages that are bleached is related to the amount of light energy and the relation is logarithmic. It is necessary to calibrate the papers with a standard light meter. We will use a solarimeter as a standard. It measures energy in all the wave lengths and shows integrated values in Wh m-2. You should calculate the regression equation for the relation of the number of pages bleached (y) to the amount of radiant energy received (x). The values for radiant energy should be transformed to their log10 before calculating the regression. You will be provided 4 radiometers. Expose them to a high light environment such as an open field and to a low light environment such as a closed forest or field of grass. Place two radiometers in each environment for a complete photoperiod. Develop the Ozalid paper and read the number of pages bleached to the nearest tenth of a page. Calculate the amount of radiant energy received by the radiometer. This data will be entered in your report and shared with the class. Report: You will be expected to show the data for the calibration including the regression equation and the graph of the curve. Also, show your own field data and the summary of the field data from the class. Then write a report explaining the results.
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