Workshop Follow-up Notes, News, and Videos
07.10.10 - Paul Adams
I am writing to encourage you to take aerosol measurements during the month of July during local solar noon. As pointed out by our colleague Todd, having a time and place to find data is useful when working with students to show data and data trends. I have been taking measurements and would like to have other join me!
I decided to keep measurements for a full day, 01 July 2010, just for the fun of it. It was a clear day, and the amount of transmittance did not change a great deal during the day ( range of 86% to 89% in the green, 89% to 95% in the red). It is important to note that the comparisons I made needed to have a constant AOT value.
I used these measurements to produce two graphs that may help clarify some of the measurements you take during the day. The first graph to look at is the relative air mass and how it changes. Note that the minimum value is around Solar Noon. No surprise here, but good to see that it is what we expect. The more interesting graph is a comparison of voltage and % transmission. What is interesting about this graph is that it clearly shows what looks like a reflection of the relative air mass for the voltage value - this makes sense since the voltage should be greatest where the relative air mass is least (assuming a constant AOT). The second part of the graph shows the fairly constant AOT value. The calculation to find the AOT value accounts for the relative air mass change. The graphs show the relations that we discussed in class. These also bring out a very important point - a Voltage reading alone does not tell you or allow you to compare AOT values - it must be calculated through the GLOBE site to factor out differences due to relative air mass etc.
Let me know how the measurements go!
07.10.10 - Paul Adams
One of the unanswered questions from the workshop was about the role of humans and if African dust was increasing. This article from Science News provides some evidence in answering the question using seafloor sediments! There is a clear link to agriculture and choice of crop dating to the 19th century! A quick read, but very interesting tie to our discussion and workshop.
Africa's bumper crop of dust
Seafloor sediments show that agriculture has greatly boosted airborne dust in the last two centuries.
Read more @