UTILIZING APPARENT SOLAR TRANSMISSION DATA FROM MAUNA LOA OBSERVATORY (HAWAII) FOR AN INTERACTIVE CLASSROOM EXERCISE AND FOLLOW-UP ASSIGNMENT

An interactive lecture and graphing exercise has been developed for an introductory-level physical geoscience course where students work with apparent solar transmission data. When lecturing on volcanism, I discuss volcanic influences on climate that can be seen in a Mauna Loa Observatory data set. Data has been compiled since 1958 of monthly averages of apparent solar transmission values which have been calculated from direct solar irradiance observations.

During a class period, students work in pairs plotting the apparent solar transmission value for a given month and year. Students graph the data on an overhead transparency sheet and answer a series of questions about trends and predictions for future data. All transparencies are overlain on an overhead projector. As a class we discuss features we see in the compiled graph, such as the notable decreases in the transmission values which they do not know at this point coincide to the timing of three major volcanic eruptions (Agung in 1963, El Chichon in 1982, Mount Pinatubo in 1991).

At the conclusion of the in-class exercise, students are required to type a summary explaining the graph. Students must clearly explain why there are the significant decreases in transmission. Students are asked if there are any other decreases in the transmission ratio they are surprised are not reflected in this global data, and they are required to use references to support their interpretations and discussion. The summary must also discuss Kilauea, and a statement as to why or why not the eruptions will be recorded in the solar transmission ratio data.

I use this exercise as the first where students work with graphing and interpreting a data set; consequently, student performance has been wide-ranging. Most groups accurately plot the data in class. Some students do not accurately correlate the dates of solar transmission decreases with volcanic eruptions. In addition, a number of students do not know how to apply what they have learned about Kilauea. Despite the range of student performance, this exercise serves as a valuable introduction to the global impact of physical processes and how to interpret that impact through working with data.

* The format of this exercise is a modification from Randall Richardson’s (Univ. of Arizona) homework problem using the global CO2 data set from Mauna Loa, Hawaii.