Meteorological Phenomena: Fog, Thunderstorms, Lightning, Tornadoes

Fog: A Cloud Phenomenon

Fog is a cloud formed by the condensation of water vapor, with its base in contact with the ground. Fogs are classified by their formation mechanism:

Fogs Resulting from Evaporation

• Smoke Fog

  Forms when cold air with low water vapor pressure passes over a warm surface. This type of fog is low-lying and common over oceans and lakes in mid to high latitudes.

• Frontal Fog

  Forms along a front where two air masses of different temperatures meet. Rain, warmer than the air it falls through, evaporates, causing the air to become supersaturated.

Fogs Resulting from Cooling

• Radiation Fog

  Forms when moist air near the ground surface cools by radiation on clear, still nights.

• Advection Fog

  Forms when moist air passes over a cold surface.

• Orographic Fog

  Forms from the adiabatic cooling of moist air as it gradually ascends the slopes of highlands.

Other Fog Types

• Mixing Fog

  Originates when two air masses, often of maritime origin, with different temperatures and humidities, mix. This mixing can lead to saturation and condensation at ground level due to the resulting lower temperature.

• Barometric Fog

  Occurs when changes in regional pressure distribution cause moist air to move into adjacent low-pressure areas, potentially leading to cooling and condensation.

Thunderstorms: Formation and Phases

Thunderstorms are produced and develop from cumulonimbus clouds in a layer of highly unstable air. Three distinct phases are observed:

• Growth Phase

  Characterized by strong updrafts that suspend rain or snow droplets within the cloud, preventing them from reaching the ground.

• Maturity Phase

  Precipitation begins as updrafts become unsustainable. Rainfall is violent, accompanied by gusts of cold air.

• Dissipation Phase

  Updrafts weaken and condensation ceases. Downdrafts produce rain and hail until the cloud's internal temperature equilibrates with the surrounding air, leading to its dissipation.

Lightning: Electrical Discharges in the Atmosphere

Lightning is a powerful electrical discharge between two centers of different electrical charge, occurring either between two regions of a cloud, between two clouds, or between a cloud and the ground. A lightning strike is formed by successive discharges that occur in split seconds.

Tornadoes: Violent Rotating Columns of Air

Tornadoes are violent rotating columns of air (vortices) extending downward from a thundercloud. They arise from the collision of air masses, where cold, dry air is positioned above warm, moist air. This creates an imbalance that causes the warm air to rise rapidly. Air entering from the sides shifts into the updraft, forming a cyclonic rotation. Their duration typically ranges from 15 minutes to an hour, but even in such a short time, their effects can be devastating.