Types of precipitation

• List 9 forms of precipitation:

Essential Question: How do different types of precipitation form?

• Types of Precipitation:Rain, drizzle, mistSnowSleetFreezing rain or glazeHailRime, graupel

• Temperature Profiles

The type of Precipitation depends on the Temperature Profile of the

atmosphere.

Temp. Profile for __________

-20°C 0°C +20°C

Below freezing Above freezing

SnowCrystals

Formation of Sleet

Rain freezes too close to the ground to have enough time to turn to snow.

Glaze

Falls as __________On the ground as __________________

Sleet

Falls as __________On the ground as _________________

RimeStarts as _________

On surfaces as ____________

FrostStarts as _________

On surfaces as ____________

What if the rain never reaches the ground?Virga: rain evaporates before it hits the ground in desert regions “rain curtain”

Formation of Hail

HailstoneCross section

HailDamage

Text book page 496

Precipitation Measurement

Rain gaugewith

metal slatsto

minimize“under-catch”

inwindy

conditions

TRUE / FALSE

Snowflakes are 6-sided crystals

There is such a thing as ‘heart-attack’ snow

It cannot snow if it’s too cold.

Skiers love ‘powder’ snow

Snow Fall Measuring

• Using a measuring stick in several locations.

• “1 inch of rain equals 10 inches of snow”

• But, the quantity of water

in snow varies…• It depends on the

temperature profile.

• WET SNOW - Wet snow is snow that has a high liquid content as it reaches the surface.

• It needs to be at least 50% made of ice or it will have more characteristics of being a raindrop instead of a snowflake.

• It gets this liquid content by partially melting before it hits the ground.

• The wetness of the snowflakes makes it easier for snowflakes to stick together as they fall, thus a wet snow will often have large snowflakes and a lower number of snowflakes

• The ratio for wet snow will be less than 10:1. For example, it takes 10 inches of snow to produce 1 inch of liquid equivalent.

• DRY SNOW- A dry snow has little to no liquid water content thus this snow will be less dense than average, there will be a lot of air pockets between the snow crystals.

• Dry snow is not sticky (it’s powdery) and thus it is difficult to make snowballs with it and the wind blows it around even after reaching the surface.

• The ratio for dry snow will be greater than 10:1. In extreme cases it can be 30:1 or greater.

• Dry snow occurs when the temperatures throughout the troposphere are well below freezing and the surface temperature is below freezing.

• Since dry snowflakes are less sticky they are less inclined to stick together as they fall, thus a dry snow will often be composed of a large number of small snowflakes.

http://www.theweatherprediction.com/habyhints/346/

Measuring Snow Equivalent

1. Fill a 100 ml graduated cylinder with “snow” _______inches2. Record the outdoor temperature ________ °C3. Find the outdoor humidity for that day ______ %4. Allow all the water melt. Record the volume. ______

inches5. Calculate the snow: water ratio ________ :_______

reduce to ______: 1

warm COLD!

Doppler Radar Display

Weather Modification

Cloud SeedingFog Dispersal

Hail SuppressionFrost Prevention

CloudSeeding

CloudDispersal

Hail Suppression

Hail Cannon

Frost Suppression

Sprinklers

WindMachines

OrchardHeaters

Role of Clouds in the Climate System