SOUTH MISSISSIPPI (WLOX) - Along the Gulf Coast, Saturday morning's temperatures have been quite chilly with much of South Mississippi chilling into the 40s and even upper 30s.
What gives? What caused our temperatures to rapidly chill overnight? It's a meteorological process called "radiational cooling." Here's an explanation:
To begin to understand radiational cooling, you must first recall that Earth has a hot molten core that is releasing heat through the earth's surface all the time. That's called geothermal heat. During the daytime, this geothermal heat is barely noticeable compared to the amount of heat that is pummeling the planet from the sun. But, at night time, geothermal heat helps to keep the earth's surface (a.k.a. the ground, where us human folk live and prosper) from becoming uninhabitably cold.
Think about this heat being released, or radiated, from the ground like your own body which releases small amounts of heat from its skin. At night, when you sleep in bed, you likely throw on a blanket to keep yourself warm. That blanket traps your body's heat right next to you instead of your heat escaping and dispersing into the room.
Well, for Earth, a blanket of clouds at nighttime can accomplish the same heat trapping process. But, on nights with calm winds without any clouds, Earth's geothermal heat radiates from the ground and disperses into the atmosphere... leaving us land-dwellers quite chilly. That's radiational cooling. And it allows temperatures to fall rather quickly during nighttime hours.
High pressure systems generally promote radiational cooling since there are typically clear skies and nearly calm winds around their centers.
Just remember: dry air + clear skies + calm winds = rapidly cooling overnight temperatures!
The WLOX First Alert Weather Team will inform you of South Mississippi's temperature forecast on-air, online, and on social media sites like Facebook & Twitter.