BISL 04-Weather and Climate

1

CONDENSATION NUCLEI

Salt, dust, smoke, and pollen, among other

particulates, serve as a surface on which

water molecules, ascending by convection,

can combine and form water droplets.

RAIN

The upper part of the cloud spreads

out like an anvil, and the rain falls

from the lower cloud, producing

descending currents.

DISSIPATION

The descending currents are

stronger than the ascending ones

and interrupt the feeding air,

causing the cloud to disintegrate..

L EVEL OF CONDENSA

T ION

0.2 inch

(5 mm)

0.07 inch

(2 mm)

0.04 inch

(1 mm)

A

Dilatation

The molecules

of water are

freeΩwater vapor.

B

Condensation

The molecules group

themselves around

a condensation

nucleus.

The air cools. The water

vapor condenses and

forms microdroplets

of water.

When the air cools, it

descends and is then heated

again, repeating the cycle.

Coalescence

The microdroplets

continue to

collide and form

bigger drops.

Anvil-shaped

Heavier drops

fall onto a

lower cloud

as fine rain.

Low, thin clouds

contain tiny

droplets of water

and therefore

produce rain.

Collision-Coalescence

Via this process,

molecules collide

and join together to

form drops.

C

-22° F

(-30° C)

STORM

CLOUD

GROWTH

The smallest clouds adhere to one

another to form larger clouds,

increasing their size and height.

The hot air

rises.

68° F

(20° C)

0.02 inch

(0.5 mm)

0.04 inch

(1 mm)

When they begin to fall,

the drops have a size of

0.02 inch (0.5 mm), which

is reduced as they fall

since they break apart.

molecules occupy 1 cubic

millimeter under normal

atmospheric conditions.

26,875

trillion

2

3

4 5

MATURATION

Mature clouds have very strong

ascending currents, leading to

protuberances and rounded

T formations. Convection occurs.

he air inside a cloud is in continuous motion. This process causes the drops of water or the crystals

of ice that constitute the cloud to collide and join together. In the process, the drops and crystals

become too big to be supported by air currents and they fall to the ground as different

kinds of precipitation. A drop of rain has a diameter 100 times greater than a droplet in a

cloud. The type of precipitation depends on whether the cloud contains drops of water, ice

crystals, or both. Depending on the type of cloud and the temperature, the precipitation

can be liquid water (rain) or solid (snow or hail).

The Rain Announces Its Coming

40 METEOROLOGICAL PHENOMENA

Rock erosion

particulates

Sea-salt

particulates

Sandstorm

particulates

Water

molecules

Oxygen

Hydrogen

Forest fire

particulates

Volcanic

particulates

Particulates from

combustion in

factories and

vehicles

0 miles

(0 km)

4 miles

(7 km)

6 miles

(10 km)

0.6-1.2 miles

(1-2 km)

WEATHER AND CLIMATE 41