Wednesday, February 21, 2018

What caused this sea of fog?

The fog at daybreak on Friday, looking towards the Central Range from Princes Town. Photo: Richard Charan

PEOPLE living in the lowlands and rolling hills of south Trinidad have for the past several days been witness to one of nature's beautiful and rare phenomenon.

Daybreak has revealed a sea of fog trapped in the valleys and hanging over the swampland.

The suspended waters droplets are so thick in some areas that drivers must use headlights, and visibility is less than 100 metres.

It lasts only minutes. Soon after sunrise, it dissipates.

The explanation is rather complicated.

What we are witnessing is a temperature inversion.

Radiational cooling, which is the cooling of the Earth's surface and the air near the surface at night, produces this type of fog.

Under stable nighttime conditions, long-wave radiation is emitted by the ground. This cools the ground, which causes a temperature inversion resulting in moist air near the ground cooling to its dew point. Depending upon ground moisture content, moisture may evaporate into the air, raising the dew point of this stable layer and accelerating radiation fog formation.