I live near equator region of Earth. During winters specifically, I see water vapors forming over the surface of the water body in the morning. Why do they form?
Air has less thermal mass than water. Without solar radiation, on a still night the air temperature will drop a lot, while a large body of water may cool very little. This can leave the surface of the water significantly above the dewpoint of the surrounding air.
Evaporation from the warmer water condenses as it is cooled by the surrounding air.
The effect is often seen in the morning because:
- Air temperatures are coolest then (most time to radiate heat away).
- Winds tend to be lighter overnight. Low winds allow evaporated moisture to remain in the area. Significant winds would disperse the moisture and the fog would not be visible.
In modern climates dew and fog are often formed in the morning as a result of condensation, since night temperatures are colder than the temperatures in the daytime. Dew point is a term that specifically means the temperature when the vapor becomes saturated and its excess must appear as condensed liquid or in a crystallized form (typically as frost).
I cannot however ascertain that it is a similar phenomenon in equatorial climates.