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