BISL 04-Weather and Climate

+ALBEDO - -ENERGYABSORBED

80%

RECENT SNOW

75%

THICK CLOUDS

50%

LIGHT CLOUDS

3-5%

WATER (WHEN

THE SUN IS HIGH)

25%

WET SAND

15%

ALBEDO OF

MEADOWS

1. 
   

7-14%

FORESTS

The Land and

the Ocean

The Sun heats the soil

of the valley and the

surrounding air, which

ascends by convection.

The air is cooled as it ascends,

becomes more dense, and

descends. Then it heats up

again and repeats the cycle.

They absorb a significant

amount of heat but remain cool

because much energy is used

to evaporate the moisture.

The air tends to

descend in forested

and rural areas.

During the night, the city

slowly releases heat that was

absorbed during the day.

The flows tend

toward equilibrium.

HEAT ISLANDS

Cities are complex surfaces. Concrete

and asphalt absorb a large quantity of

heat during sunny days and release it

during the night.

WARM AIR WHIRLWINDS

Intense heat on the plains can generate a hot, spiral-

formed column of air sometimes more than 300 feet

(100 m) high.

ON THE LAND

During the day, the land heats up

more rapidly than the ocean. The

warm air rises and is replaced by

cooler air coming from the sea.

Because it is

opaque, the heat

stays in the

surface layers,

which are

heated and

cooled rapidly.

When night

falls, the land,

which was hot,

cools rapidly.

When night

falls, the water

is lukewarm

(barely a

degree more

than the land).

The heat

penetrates into

deeper layers

thanks to the

transparency of

the water. A

part of the heat

is lost in

evaporation of

the water.

LAND

WATER

COLD AIR

WARM AIR

IN THE OCEAN

From the coast, the ocean receives

air that loses its heat near the

water. As a result, the colder air

descends toward the sea.

IN THE OCEAN

The loss of heat from the water is

slower.

2. 
   

ON THE LAND

During the evening, the land radiates

away its heat more rapidly than the

water. The difference in pressure

generated replaces the cold air of

the coast with warm air.

In the interior of a landmass,

there is a wide variation of

daily temperatures, while on

the coasts, the influence of

the ocean reduces this

variation. This continentality

effect is quite noticeable in

the United States, Russia,

India, and Australia.

Isotherms in a typical city

Continentality index

Daily variation of temperatures

in the United States

Less More

26 SURFACE FACTORS

WINDS OF THE MOUNTAINS

AND VALLEYS

COASTAL BREEZES

CONTINENTALITY

1

Cold air currents descend from the

mountainside toward the floor of

the valley, which is still hot.

1

2

The air currents

are heated and ascend by

convection. When they rise, they

cool and once again descend along the

mountainside.

MOUNTAINSIDE

VALLEY

VALLEY

WARM-AIR

FLOW

COLD-AIR

FLOW

STRONG WIND

MILD WIND

SLOPE

2

82° F

84° F

84° F

82° F

84°F 86°F 88° F

82°F 90°F

90°F 86°F 82° F

88°F 84°F

82° F

84° F

84° F

82° F

81° F 81° F

1 Strong, high-speed winds move on

top of weaker winds and cause the

intermediate air to be displaced like

a pencil on a table.

1

A powerful air

current lifts the

spiral.

2

LAND

WATER

COLD AIR

WARM AIR

WEATHER AND CLIMATE 27

T

emperature distribution and,

above all, temperature

differences very much depend

on the distribution of land and water

surface. Differences in specific heat

moderate the temperatures of regions

close to great masses of water. Water

absorbs heat and releases it more

slowly than the land does, which is

why a body of water can heat or cool

the environment. Its influence is

unmistakable. Moreover, these

differences between the land and the

sea are the cause of the coastal winds.

In clear weather, the land heats up

during the day, which causes the air to

rise rapidly and form a low-pressure

zone. This zone draws marine breezes.

KEY

Chinook WINDS

These winds are dry and warm, sometimes quite hot,

occurring in various places of the world. In the western

United States, they are called chinooks and are capable

of making snow disappear within minutes.

MOUNTAIN WINDS

Humid winds are lifted over

the slopes, creating clouds

and precipitation on the

windward side. These are

called anabatic winds.

The dry and cool wind

descends down the

mountain slope on the

leeward side. It is

called katabatic.

WINDWARD

LEEWARD

Autan wind
Berg
Bora
Brickfielder
Buran
Harmattan
Levant
Mistral
Santa Ana
Sirocco
Tramontana
Zonda

Winds Characteristics Location
Dry and mild
Dry and warm
Dry and cold
Dry and hot
Dry and cold
Dry and cool
Humid and mild
Dry and cold
Dry and hot
Dry and hot
Dry and cold
Dry and mild

Southwestern France

South Africa

Northeastern Italy

Australia

Mongolia

North Africa

Mediterranean region

Rhône valley

Southern California

Southern Europe and North Africa

Northeast Spain

Western Argentina

Factories and vehicles emit

large amounts of heat into

the atmosphere.