Precipitation Types
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Precipitation Types. Global and Regional Mean Precipitation 1. Types of Precipitation: 2. Measurement:. FIT, Feb 15, 2012. Global Mean Precipitation. Satellite measurement of precipitation What happens in Hawaii?. Hawaii Mean Precipitation. Mean = 70 in Without land = 25 in.

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Precipitation types

Precipitation Types

Global and Regional Mean Precipitation

1. Types of Precipitation:

2. Measurement:

FIT, Feb 15, 2012


Precipitation types

Global Mean Precipitation

Satellite measurement of precipitation

What happens in Hawaii?


Hawaii mean precipitation

Hawaii Mean Precipitation

Mean = 70 in

Without land = 25 in

Precipitation measurement by Rain Gauge


Honolulu mean precipitation

Honolulu Mean Precipitation


Precipitation types

Surface Analysis (Feb 11, 2012, 18 UTC)


Precipitation types

Hawaii (Feb 12, 2012, 0245 UTC)

Radar measurement of rain


Precipitation types

Precipitation Types


Precipitation types

Precipitation Types

  • Drizzle: diameter < 0.5 mm

  • Rain: diameter >= 0.5 mm

  • Where are the raindrops larger, Miami or Seattle?

  • Raindrops almost always < 6 mm because

  • collision among raindrops

  • too large raindrops tend to break up

  • Start as rain, but may fall as drizzle.

Does rain always reach the surface?


Precipitation types

Does rain always reach the surface?

  • Falling precipitation that evaporate before reaching surface --- Virga

  • Low humidity - - evaporation - - drops become smaller - - rate of fall decreases

  • Strong updraft

  • Sudden rain shower and cloudburst (Cumuliform)

  • Rain and no-rain in places next to each other (Cumulonimbus)

  • Continuous rain at small vertical currents (layered cloud or Nimbostratus)

How does “Virga” look like and where does it happen?


Precipitation types

Virga (Rain not reaching the surface)

Fig. 7-14, p. 174


Precipitation types

Shape of Raindrops

Spherical < 2 mm ; Parachute > 2 mm

(surface area / volume) is minimum for 2.

Fig. 2, p. 175


Precipitation types

Intensity of Rainfall

Table 7-2, p. 175


Precipitation types

Precipitation Types


Precipitation types

Snow

c

Falling ice-crystals and snowflakes (Fallstreaks)

from cirrus clouds.

Fig. 7-15, p. 176


Precipitation types

Common forms of ice crystal

Fig. 7-16, p. 176

Why is dendrite

most common?

Dendrite

Fig. 7-17, p. 178


Precipitation types

Why is dendrite most common?

Growth = f(temperature, sat. vap. Pr. difference)

Maximum growth rate is at -12 to -16 C, when saturation vapor

pressure difference between water and ice is maximum.

Table 7-3, p. 176


Precipitation types

Intensity of Snowfall

Is visibility the best way to measure snowfall?

Can wind lead to visibility problem?

Table 7-4, p. 178


Precipitation types

Some more terms related to snowfall

Flurries: light and intermittent from developing cumulus cloud

Snow squall: brief but more intense than flurries, usually from cumuliform clouds

Drifting snow: surface movement

Blowing snow: in air movement

Ground blizzard: after falling snow has ended

Blanket of snow: snow covering the landscape

Fig. 4, p. 179


Precipitation types

Snow as Sound Absorbant

Fig. 4, p. 179


Precipitation types

Annual Average Snowfall over US

Why is Hawaii not included?

Fig. 7-18, p. 179


Snow in hawaii

Snow in Hawaii !!

Mauna Kea


Precipitation types

Precipitation Types


Precipitation types

Sleet and Freezing Rain

Partially melted snowflake or cold raindrop - - freezes

Deep freezing layer - - Sleet <= 5 mm

Shallow freezing layer - - freezing rain >=0.5 mm

Fig. 7-19, p. 180


Precipitation types

Formation of Rime

Supercooled droplets in contact with object at below freezing temperature - - white milky granular ice

Fig. 7-20, p. 180


Precipitation types

Destruction due to Freezing Rain

Syracuse, New York, January 1998

Fig. 7-21, p. 180


Precipitation types

Aircraft de-icing

Fig. 5, p. 181


Precipitation types

Average number freezing rain/drizzle days

Fig. 7-22, p. 181


Precipitation types

Vertical Temperature Profile and Precipitation Type

Fig. 7-23, p. 182


Precipitation types

Precipitation Types


Precipitation types

Snow Grains and Snow Pellets

Fig. 4, p. 179


Precipitation types

Formation of Graupel / Snow Pellets

gr

Ice particle + cloud droplets -- rimed ice crystal -- graupel (dift shape than rime) -- snow pellet

During summer: graupel - - large raindrop

Vigorously convective cloud: graupel - - hailstones

Fig. 7-24, p. 182


Precipitation types

Formation of Hail/Hailstone

Fig. 7-27, p. 183


Precipitation types

Hail and Hailstone

Dia = 17.8 cm (7 in) ;

Circumference = 47.6 cm (18.7 in);

weight > 1.75 lb

Fig. 7-25, p. 182

Fig. 7-26, p. 183


Precipitation types

Summary of Precipitation Types

Table 7-5, p. 185


Precipitation types

Measurement of Precipitation

In-situ measurement: Rain gauge; accurate but spotty.

Remote measurement: Radar, Satellite; not so accurate but large coverage.

Combination of the above.


Precipitation types

Components of the standard rain gauge

Area of collector = 10 x area of measuring tube

Fig. 7-29, p. 184


Precipitation types

Tipping bucket rain gauge

Fig. 7-30, p. 185


Precipitation types

Transmitted energy

backscatter

Radar


Precipitation types

Reflectivity

Precipitation

Oklahama, April 24, 1999

Fig. 7-31a, p. 187


Precipitation types

Precipitation due to Fay (2008)

Precipitation

Reflectivity

Fig. 7-31a, p. 187


The end

THE END


Precipitation types

Fig. 7-23a, p. 182


Precipitation types

Fig. 7-23b, p. 182


Precipitation types

Fig. 7-23c, p. 182


Precipitation types

Fig. 7-23d, p. 182


Precipitation types

Fig. 7-28a, p. 184

Fig. 7-28b, p. 184


Precipitation types

Fig. 7-32, p. 189


Precipitation types

Fig. 7-32, p. 189


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