In the GLOBE Clouds protocol and GLOBE Observer app, you can report if your sky is “overcast” or “obscured”. But what’s the difference? Below are some tips to help! All the photographs featured were collected by observers just like you - Thank you!
I found “obscured” and “overcast” very confusing at first, but when I understood what they meant, things made much more sense. Let’s start by defining them:
Overcast – The sky is completely covered by clouds (cloud cover greater than 90%). This means that you will see little or no blue sky. When it’s overcast, you are looking at stratus clouds. Stratus are gray or grayish white.
Obscured – Something is blocking your view of the sky AND the clouds. This could be dust, haze (pollution), smoke, volcanic ash, and even heavy rain or snow. Snow will appear white, but other obscurations may give the sky a brownish or orangish hue.
Tip from Dr. Brant Dodson (NASA/SSAI) - smoke and dust often change the color of the sun, while clouds (thin enough to not cover the sun) do not. This might be helpful in situations where it is difficult to distinguish between clouds, smoke, and dust. REMEMBER - NEVER LOOK DIRECTLY AT THE SUN.
Overcast – tilt your camera at 14 degree angle up at the sky. If you are using the GLOBE Observer app, the app assists you and automatically takes the photo when your device is titled at the right angle.
Obscured - look straight ahead at the horizon. The same way as when making visibility reports. If you are using the GLOBE Observer app, follow these steps to submit a photograph of the horizon. The example in these steps is for dust. Make sure to select the obscuration that you actually see (e.g., smoke, haze).
An obscuration can be mixed with clouds. If the obscuration covers 30% or more of your view of the sky, then only report the obscuration observed. Use the steps above to take your photographs.
Image source: https://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Haboob_Ransom_Canyon_Texas_2009.jpg/1200px-Haboob_Ransom_Canyon_Texas_2009.jpg
Use these tips to make cloud observations.