Marine meteorology

2nd November 2011

Precipitation

Marine Science DepartmentFisheries and Marine Science Faculty

Padjadjaran University

Outline

Overview: precipitation & condensation

Precipitation’s Importance

Types

Steps of Precipitation

Frontal systems

Precipitation data

Rainfall

Terms

Tutorvista.com (2011)

Condensation

• Condensation occurs when water vapor changes to a

liquid.

• For condensation to take place, the air must be saturated

and there must be a surface on which the vapor can

condense.

• In the air above the ground, tiny hygroscopic (water-

absorbent) particles known as condensation nuclei

serve as the surfaces on which water vapor can condense.

Cloud Heights

• Cloud heights can be either:

high, with bases above 6000 meters.

middle, from 2000 to 6000 meters, or

low, below 2000 meters.

• Based on the two criteria, ten basic cloud types,

including such types as cirrostratus, altocumulus,

and stratocumulus, are recognized.

Cloud Types

Precipitation’s importance

Agriculture

Fisheries

Lakes

Human’s need

etc

bangkittani.com

Usatoday.com

poleshift.ning.com

Precipitation Types

• The two most common and familiar forms of

precipitation are:

RAIN (drops of water that fall from a cloud and

have a diameter of at least 0.5 millimeter) and

SNOW (precipitation in the form of ice crystals or,

more often, aggregates of ice crystals).

Flicker.com Warebuzz.com

Precipitation Types

• Other forms include: Sleet (falling small particles of ice that are clear to translucent),

Glaze (formed when supercooled raindrops turn to ice on

colliding with solid objects),

Hail (hard, rounded pellets or irregular lumps of ice produced in

large cumulonimbus clouds), and

Rime (a deposit of ice crystals formed by the freezing of

supercooled fog or cloud droplets on objects whose surface

temperature is below freezing).

• Drizzle (smaller droplets of rain, yet larger than mist)

• Mist (smallest water droplets visible)

• Gaupel (watery hail)

Sleet

falling small particles of

ice that are clear to

translucent

ww2010.atmos.uiuc.edu

Glaze

formed when

supercooled raindrops

turn to ice on colliding

with solid objects

Hailhard, rounded pellets or irregular

lumps of ice produced in large

cumulonimbus clouds

climate.met.psu.edu

•Gaupel (watery hail)

Drizzle

(smaller droplets of

rain, yet larger than

mist)

Mist : smallest water droplets visible

dsumantriphotography.wordpress.com

Rime Ice

Hail

Sleet formation

Rime (a deposit of ice

crystals formed by the

freezing of supercooled fog

or cloud droplets on

objects whose surface

temperature is below

freezing).

Steps:

Precipitation occur when 3 conditions met :

1. Atmosphere is saturated.

2. Small particles are present ; dust, ocean salt,

etc.

3. Drops are big enough to reach the surface.

Atmosphere Saturated

Atmosphere becomes saturated When the air masses is

cooled by lifting.

Air masses lifting caused by:

- Frontal system (warm fronts/cold fronts)

- Orographic effect (induced by mountain); rain shadow

produces deserts.

- Convection ; summer thunderstorms

Frontal System

Cold Fronts

- High intensity

- Short duration

- Narrow zone

Warm Fronts

- Gentle rainfall

- Long term

- widespread

Orographic precipitation

Increasing rainfall with increasing elevation

krygier.owu.edu

Orographic precipitationMechanisms of orographic

precipitation:

(a) Seeder-Feeder mechanism;

(b)upslope condensation;

(c) upslope triggering of

convection;

(d)upstream triggering of

convection;

(e)thermal triggering of

convection;

(f) leeside triggering of convection;

(g) leeside enhancement of

convection. Slanted lines below

cloud base indicate

precipitation.

[From Fig. 12.24 of Houze, 1993].

Convective Precipitation

High intensity

Short duration

Limited area

It results from the heating of

the earth's surface that causes

air to rise rapidly. As the air

rises, it cools and moisture

condenses into clouds and

precipitation. This type

of precipitation is common in

the prairie provinces.

Precipitation Terms

Hystograph : a plot of rainfall intensity vs time

Isohyete : Contours of constant rainfall, similar to contours

of constant elevation.

Isohyetal map : Map with contours of constant rainfall.

Rainfall (mm) at Bantar Dewa Ciamis station

Rain Measurement

• Rain, the most common form of precipitation, is

probably the easiest to measure.

• The most common instruments used to measure

rain are:

the standard rain gauge, which is read directly, and

the tipping bucket gauge and weighing gauge,

both of which record the amount of rain.

A standard rain

gauge

Marine meteorology

2nd November 2011

Thanks a lot

Marine Science DepartmentFisheries and Marine Science Faculty

Padjadjaran University