Nov 23, 2019
Can you predict the weather from a photograph (without Machine Learning)
An excerpt from the book “How to” by Randall Munroe.
We tend to be so dependent on technology for each and every small task. Suppose we don’t have any technology that can predict the weather. Can we somehow predict it by looking at the sky. Or by a photograph posted in Instagram or Facebook?
There seems to be a promising method/thumb of rule by which we can predict the weather based on the sky color. The old saying goes as
“Red sky at night, sailor’s delight. Red sky at morning, sailors take warning”
But how!!!
Points to remember
- In temperate zones, weather systems (clouds, winds etc) move from west to east very slowly.
- Red wavelengths pass through air more easily than blue ones (reason behind traffic signal stop color)
- Last but not least, Sun rises in east and sets in West.
So, when the Sun is setting in the west, its light passes through hundred of miles before becoming extremely red, and before hitting the clouds above you. Shorter blue wavelengths bounce off the air and go off in other directions (reason for sky to be blue). White clouds reflect all colors, so when red light shines on them, they look red too.
Scenario 1 — Red sky at night
When weather moves from west to east, a red sky at night means that there are clouds overhead, but clear skies to the west — which tells you that the weather will likely be clearing up (means it might not rain)
Scenario 2 — Normal sky
If there are storm clouds to your west, the red sunlight will be blocked by them even before reaching you, so the sunset doesn’t look red.
Scenario 3 — Red sky at morning
If there’s clear air for hundreds of miles to your east, the sunlight passes all the way through to reach the sky above you, turning it red. If there are any clouds overhead, the red light illuminates them, creating a spectacular sunrise.
A red sky in the morning means that there is clear air to the east…but clouds overhead. That means the clear zone is moving away, and clouds are moving in (means it might rain)
This is the reason why some photographers can capture excellent images during sunrise and sunset. They call it the “Golden hour” where the background of a picture can be so red thus so good looking. So, the old saying can be converted as:
“Post good pics in the evening, then the bad weather is leaving. Morning selfies go viral, there’s a low-pressure spiral”
Note: This technique might not work in tropics zone because of unpredictable movement of winds and a much more stable weather. To know in which zone you are in, check the below image.
To understand more interesting stuff like
- “How to take a selfie with planets”
- “How to transport your house”
- “How to power your house” (In Earth and in Mars as well)
- “How to charge your phone when you don’t have a charger” etc;
Read the book “how to” by Randall Munroe.
During your childhood, some of your crazy questions which start with “How” will be answered in this book. It also offers few tips to “How to dispose this book” at the last chapter, in case you won’t find the book to be useful or find it dangerous. Pretty cool isn’t it !!
Note: The author maintains a website called xkcd (a web-comic). And this comic (https://xkcd.com/1732/) describes the timeline of temperature change from the Ice-age and where we are heading towards in global warming, greenhouse effect which predicts the dystopian future if we don’t start acting on it.
Personal Website: namburisrinath.github.io
Medium Handle: namburisrinath.medium.com
LinkedIn: https://www.linkedin.com/in/namburi-gnvv-satya-sai-srinath/
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