Hydrometeorological Phenomena
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What are HYDROMETEORS?

They are water particles, liquid or frozen, that have formed in
the atmosphere or at the Earth's surface due to condensation
or sublimation.

The particles can:
- Fall through the atmosphere.
- Be suspended in the atmosphere.
- Be blown from the ground into the atmosphere by the wind.
- Be deposited on objects.

What are the different kinds of HYDROMETEORS?

Rain: It is the precipitation of liquid water particles in the form of drops of more than 0.5 mm in diameter.

Drizzle: It is the precipitation of liquid water particles in the form of droplets with a diameter of less than 0.5 mm.

Snow: It is the precipitation of ice crystals. Many of them are branched structures, sometimes in the shape of stars.

Snow Grains: It is the precipitation of very small, white, opaque grains of ice similar in structure to snow crystals. They are flattened and elongated. Their diameter can vary between 2 and 5 mm.

Snow Pellets: It is the precipitation of small snow grains, white and opaque, generally round . Their diameter is smaller than 1 mm.

Ice Pellets: It is the precipitation of transparent or translucent little balls of ice, with a diameter of 5 mm or less.

Hail: It is the precipitation of ice balls ranging in diameter from 5 to 50 mm, sometimes ever more.

Ice Crystals (Ice Prisms): It is the precipitation of unbranched ice crystals in the form of needles, columns, or plates.

Fog: It is the suspension of minute water particles (droplets) that reduce horizontal visibility to less than 1 km.

Mist or Ground Fog: It is the suspension of microscopic water droplets that reduce horizontal visibility to 1 km or more.

Drifting and Blowing Snow: Snow particles raised from the ground by the wind. Drifting snow is made up of snow particles raised by the wind to small heights above the ground. Visibility is not significantly reduced. Instead, blowing snow is snow particles raised and stirred violently by the wind to a height of 1.5 km or more, affecting visibility considerably.

Dew: A deposit of water drops on objects at or near the ground produced by condensation of water vapor from the surrounding clear air.

Hoar Frost: A deposit of ice having a crystalline appearance, generally assuming the form of scales, needles, or fans.

Glaze (Clear Ice): A coating of ice, generally clear and smooth. It is formed by the freezing of super-cool drizzle or rain drops on exposed objects at temperatures below or slightly above 0°C.

Jaquelina Michienzi
Senior Meteorologist-Expert on
Camera Meteorologist
The weather Channel LatinAmerica
Abril 2001