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Here Comes the SunYou Can Help Scientists Measure Haze in the Atmosphere
by Carolyn Staudt
I recently flew across the country to work with one of the Concord Consortium's research sites. Mt. Baker High School is nestled in the pristine mountains just outside of Bellingham, Washington, where the skies are blue and the clouds circle snow-capped mountains that appear within walking distance. When you breathe the air, your lungs beg for more. Furthest from my mind were the sulfur and nitrogen oxide gases, carbon monoxide, hydrocarbons, and airborne particles that often reduced my former home state of Ohio to only seventy clear sunny days a year.
Haze is a result of the natural suspension of water vapor, windblown dust, pollen, and volcanic ash in the air. However, much of particulate matter floating in our air- and throughout the world- is a hallmark of the industrial age. These airborne particles interfere with our vision and the level of visibility by scattering, obscuring, refracting, or reflecting sunlight and moonlight. Look toward the horizon. Are you fortunate to live in a location that is free of haze? Thanks to Forrest M. Mims, III, students and teachers across the country are able to construct a simple, inexpensive instrument to measure haze. The Global Lab VHS-1 apparatus he developed is an electronic kit assembled inside a VHS video cassette box. The VHS-1, called a sun photometer, measures the intensity of direct sunlight. Since haze interferes with the transmission of direct sunlight, this instrument can also measure the amount of haze. Particles in the air scatter more at the blue part of the spectrum, so if the light being measured has gone through a lot of hazy air, the registered signal is noticeably reduced. Forrest has been using photometers like this for years and is confident that, if used carefully, they can be accurate to within a few percent.
Much more data about haze are needed. Daily observations at many places would help enormously. These data might find and track thin haze "clouds" which might be filtering out more ultraviolet radiation than is realized. This might explain why few ground-level increases in UV are observed, even though we know ozone in the upper atmosphere, which blocks UV, is thinning. While decreased UV sounds good, UV also kills infectious agents like bacteria and viruses and even repels some mosquito larvae, so its reduction might result in illness. Haze also obscures satellite photographs. These photographs can be greatly enhanced if the amount and distribution of haze in the pictures was accurately known.
The following describes some of the ways Haze-SPAN is being used in education. We hope readers will add to this list. Global Lab Forrest designed the sun photometer for the TERC Global Lab curriculum which includes haze studies. Global Lab provides the curriculum base for extended student investigations, one of which is haze research. Scope, Sequence, and Coordination Last summer Mims tested an easily-built version of the sun photometer in NSF/NSTA teacher workshops with 84 teachers, and with students from ten nations at the University of Nations. Clearly defined protocols for calibration, data gathering, and calculations developed by TERC and NSTA enabled students to take on the role of the scientist. Blue Skies Forrest and I are developing a three-part atmospheric science unit for the Kids As Global Scientists project at the University of Michigan with Nancy Songer and Perry Sampson. One goal of this project is to develop large scale Web-based curricula that use data collection. Under development are activities that allow students to take measurements of the atmosphere with simple equipment, such as colored filters and, of course, the sun photometer. The plan is to make a souped-up model of the sun photometer that will measure haze as well as ultraviolet light. NetAdventure Starting this summer, we are offering informal learning opportunities over the net (see "Join NetAdventure"). One of the NetAdventure activities will be to build and use a sun photometer. Hands On Physics We are creating a new, online, project-based approach to physics called Hand On Physics. One of the eight units uses haze measurements as a way of introducing the basic physics of light and the technologies of light detection. Haze-SPAN is part of a growing effort to use technology to engage students in authentic science as a means for learning about important science content as well as the process of science. The Haze-SPAN Web site contains pointers to the growing literature on this topic and lists examples of where these "student scientist partnerships" can be found. By arming students with a powerful scientific tool and linking them throughout the world, we hope that learners everywhere can become empowered to better understand the impact forces impacting their environment.
Carolyn Staudt checks out the Haze-SPAN Web site, where anyone can download instructions for building a sun photometer for measuring atmospheric haze.
You can check out the Haze-SPAN Web site too! | ||||
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