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Measuring SolarAureoles with ADI
Morton M. Sternheimwww.umassk12.net/digital
June, 2011
What is a Solar Aureole?It is a bright glow around the sunCaused by aerosols – suspensions of fine particles
or liquid drops in the airAerosols are usually dust, smoke, smogAureole is larger when the concentration is higherRain will tend to wash out aerosolsADI can quantify aureoles and provide air quality
data
When Are Particulate Levels High?When the weather is calm,
allowing pollution to build up. Around factories, during
rush hour and near busy roads.
When there is smoke in the air from wood stoves, fireplaces, forest fires or burning vegetation.
Source http://www.mass.gov/dep/air/aq/aq_pm.htm
Sun and Sky Photography, Forrest Mims, http://www.sunandsky.org/Sky_Photos.html
Effect of Dust (Texas)
Mexican smoke
Sahara dust
Clear sky
Mauna Kea Summit
Aureole
No aureole
Blue intensity
Particulates Can Cause DiseaseAsthma and chronic bronchitis Acute respiratory symptoms, such as coughing and
chest tightness Decreased lung function, experienced as shortness
of breathHeart attacksPremature death in people with heart or lung
disease
Safely Photographing AureolesDo NOT look directly at the
sun; you can damage your eye
Method 1. Use building roof or wall edge to mask sun
Method 2. Use black ball or disk on rod, align camera with shadow (Mims)
Thursday, Sept 16, 2010 (before rain)
Friday, Sept. 17, 2010 (after rain)
Analyzing With ADI Open picture Spatial analysis (button)
Select Spatial Tool Line Tool
Click and drag a line across the areole
File Draw color across line
Thursday, September 16, before rain
Friday, Sept. 17, 2010 (after rain)
ObservationsThe aureole is smaller after rain has washed out aerosolsIn the second (after the rain graph), relative to the blue
component, there is a much steeper drop off in intensity for the red and to some extent the green component. (The red peak is much sharper).
Longer wave length light (red) scatters mainly from the larger particles in the atmosphere, and the rain has washed out much of this material. (If there are no aerosols, there is no aureole, and you just get a blue sky - the blue intensity plot is almost flat as you go away from the sun.)
CoronasColorful halos around the
sun (or moon)Generally due to ice crystals
or water droplets; sometimes pollen
Corona due to juniper pollen in Texas (Mims)
Technical detailsTry to take the photos from the same location and
about the same time each day. I took mine near noon. The same zoom is also desirable.
You will need a size scale for detailed comparisons. Select an object or building feature and assign it an arbitrary size. Use the same object and size in analyzing each photo.
Air Quality DataEPA AIRNOW – particulates, ozone
http://www.airnow.gov/
Massachusetts Department of Air Quality http://www.mass.gov/dep/air/airquali.htm
Some Research QuestionsHow do the ADI measurements correlate with reported
Particulate Matter levels?What happens when it is very dusty, perhaps from winds
blowing across recently plowed fields? Can you see the effects of pollen?Can you see the effects of dust from an Icelandic volcano
coming around the globe to here?What does the aureole look like after a hurricane or
northeaster? Will classes in urban and rural areas get the same results at a
given time?
ReferencesHow to Analyze Digital Images, Forrest Mims, The
Citizen Scientist Sun and Sky Photography, Forrest Mims,
http://www.sunandsky.org/Sky_Photos.htmlDavid R. Brooks, March 2008, Photographing the
Solar Aureole: A Different Way of Looking at Particulates and Scattered Light in the Atmosphere http://www.instesre.org/Solar/AureolePhotography/Aureole.htm