eli5: How do meteorologists determine when sunrise and sunset occur (down to the minute) if it’s still light or dark outside visually?

Question

I was looking at the weather app and, from where I live, sunset occurs exactly at 7:16 pm. Outside, the sky is a dark blue but still light enough to see and navigate the world. On the weather app it displays “Civil Twilight”, “Nautical Twilight”, and “Astronomical Twilight”. If these sunset periods occur after 7:16, then how do we know that sunset occurs exactly at 7:16 and not at these other time periods?

In: Planetary Science

Answer 1

Sunrise and sunset are astronomical phenomena, not meteorological, and are defined by the Sun’s position relative to the horizon. For sunrise and sunset, this is when the upper rim of the sun is at the horizon. Civil twilight is between this and 6 degrees below the horizon, and nautical twilight is between 6 and 12 degrees.