Moisture Coldest Warmest month Tropical ClimatesImportant Climate Types for the Tropics • Tropical wet climate –Rain all year round –Short dry season - Monsoon –Winter dry

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Tropical Climates

Tropical Horticulture - Texas A&M University

Koeppen’s Climate ClassificationMoisture Coldest

monthWarmest

month

Tropical - >18C -

Dry Evap>Rain - -

Temperate - <18C, >-3C >10C

Cold - < -3C >10C

Polar - - <10C


Koeppen’s Climate Classification


Important Climate Types for the Tropics

• Tropical wet climate– Rain all year round– Short dry season - Monsoon– Winter dry season

• Semi arid (< 750 mm)• Desert or arid climate


Climates in the Tropics


Climate Determinants

• Solar radiation• Surface receiving solar radiation• Earth’s rotation• Land/sea configuration and topography

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High solar radiation with little seasonal variation (6%) at the Equator

Solar Radiation at the Equator

100

200

300

400

500

JanFeb Mar

AprMay

JunJuly Aug

Sep Oct NovDec

Sola

r R

adia

tion

(W/m

2/da

y)

0


20% seasonal variation in solar radiation at 20° N latitude

Solar Radiation at the Equator and 20 N

100

200

300

400

500

JanFeb Mar

AprMay

JunJuly Aug

Sep Oct NovDec

Sola

r R

adia

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(W/m

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y)

020


Less solar radiation with much seasonal variation (50%) at 40° N

Solar Radiation at the Equator, 20 N and 40 N latitude

100

200

300

400

500

JanFeb Mar

AprMay

JunJuly Aug

Sep Oct NovDec

Sola

r R

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(W/m

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02040


Solar Radiation AbsorptionReceiving Surfaces

• Land• Bare soil• Dry soil• Dark soil

• Warmer• Low

• Low

• Water• Vegetation• Wet soil• Light soil

• Cooler• High

• High

Temperature

Pressure

Airflow

Humidity


Solar Radiation Drives the Climatic System

• Tropical Region– High consistent levels of incoming

solar energy– 75% of surface as water - thus

much moisture


Air Flow in the Tropics• High solar input heats up

air– Warmer air rises– Creates a low pressure area– Causes air flow from the

higher pressure zone at higher latitude

• Trade winds are the result

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Tropical Trade Winds


Intertropical Convergence Zone

• ITCZ where trade winds converge

Tropic of Cancer - 23.5° N

Tropic of Capricorn - 23.5° S

Equator Intertropical Convergence Zone



• ITCZ follows the sun and modified by topography

Equator Intertropical Convergence ZoneJuly

January


Moisture

• Air temperature is correlated to water holding capacity of air

• Tendency for higher rainfall in tropics– Can be very intense showers– Associated with the ITCZ


Color codes:Reddish tones = no dry seasonBlue tones = short dry season

Yellow and green = distinct dry season

Temperature of the coldest month is > 18C (64.4F)Temperature of the coldest month is > 18C (64.4F)

Highestrain

alongthe

ITCZ



Annual evaporation exceeds annual precipitation

Color codes: Grays and blue = steppe climateShades of orange = desertsYellows = cool dry deserts


The major deserts of the world are towards edge of tropical zone

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Temperature in the Tropics• Little annual variation (<10°F or 6°C)

• Daily range is typically greater than mean monthly temperature range

• Cooler temperatures at higher altitude– 3°F/1000 feet or 5.6°C/1000 m

• Warmer temperatures in continental interiors


What is the Tropics?• Three climate influencing characteristics

unique to the tropics– High solar radiation– Little seasonal variation in solar radiation– 75% of surface area is water

• Main classification points– Moisture– Altitude

• No one unique tropical climate– Very wet to very dry– Windy to relatively calm– Very hot to cold

Tropical Soils


Tropical vs Temperate Zone Soils

• Older land surfaces– Most temperate areas exposed since last

glaciation– Exceptions: volcanic and alluvial soils

• More highly weathered and leached– High temperature/moisture – Weather 4 times faster– Poor natural fertility


Old Landscape Soils

• 54% of land area– Oxisols, 25%

• Brazil and Zaire

– Ultisols, 12%• Brazil, West coast of Africa, NE India, Borneo

– Alfisols, 17%• Sahelian and Sudanian zones• Kenya, Tanzania, NE Brazil, India


Oxisols in the Tropics

OO

O O OO

O

OO

O

O

O

25% of land area

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Oxisols - 25%• Humid tropics• Low pH• Low CEC• Low exchangeable bases, Al, P• Low fertility• Excellent drainage• Good to excellent erosion resistance• Agricultural potential

– Low in low input system– High in high input system


Ultisols in the Tropics

U

U

UU

U

U

U

U

U

U UU

U U U

U

12% of land area


Ultisols - 12%• Humid tropical forest, Asia• Low pH• Low CEC• Low exchangeable bases, P - high Al• Low fertility• Excellent drainage• Poor to good erosion resistance• Agricultural potential

– Low in low input systems– Good - high in high input system


Alfisols in the Tropics

A

A A A

AA

A

A

A A

A

A

A

17% of land area


Alfisols• Transitional zone to arid climate• High pH• Medium CEC• Medium to high exchangeable

bases• Medium to high fertility• Good to excellent drainage• Poor to good erosion resistance• Agricultural potential

– Good for low input system– High for high input system


New Landscape Soils

• Alluvial, Volcanic, and other soils 23%– Entisols and Inceptisols

• Desert soils 20%– Aridisols

• Cracking soils 3%– Vertisols

• Peaty soils <1%– Histosols

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Inceptisols and Entisols in the Tropics

I

II

I

I

I

I

I I I

I

I I

I

I

I

I

I I

I

I

I

I

EE

E

EE

E

E

EE

23% of land areaTropical Horticulture - Texas A&M University

Inceptisols and EnceptisolsNew, little weathered soilsVary in characteristics


Alluvial Soils• River flood plains• Wide range of physical/chemical traits• Very fertile• Flood control is important• Location - Tropical River Basins

– Amazon, Orinoco– Congo, Senegal, Niger– Ganges, Mekong

• Already extensively farmedTropical Horticulture - Texas A&M University

Volcanic soils


Volcanic Soils• Advantages

– Excellent drainage– Stable porous structure, resistant to erosion– No drought or tillage problems– Abundant Ca, Mg, and K

• Disadvantages– P fixation and low N– Generally at high altitude

• Cooler climate• Poor access

– Already extensively farmedTropical Horticulture - Texas A&M University

Aridisols in the Tropics

DDD

D D

D

D

D

D

D

D

D D

D

20% of land area

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Aridisols - Desert soils• Developed in dry regions so little

weathering• Little leaching so good fertility• May have accumulations of sodium,

gypsum, or salt

• Potential if water is available for irrigation and leaching


Vertisols in the Tropics

VV

VV

V

3-5% of land area


Vertisols• Characteristics

– High in montmorillonite clay– Cracks when dry– High pH, Ca, and Mg– Good fertility– Excellent potential for

agriculture• Disadvantages

– Difficult to till if dry or too wetTropical Horticulture - Texas A&M University

Histosols• Soils with peaty accumulations• 75% of these soils in SE Asia

• Sumatra, Borneo, Indonesia

• Most have low base status• Good N levels• Low P, K and other cations• Micronutrient deficiencies (Zn,

Cu) common


Histosols - Peaty soils• Soils with peaty accumulations• Need to be drained before use

• Deep peats, pineapple production• Shallow peats, rubber, oil palm, coffee


Fertility Levels of Tropical Soils

• Alluvial most fertile• Vertisols• Aridosols• Volcanic• Alfisols• Ultisols• Oxisols least fertile

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Extent of Tropical Soils

• Oxisols 25%• Aridisols 20%• Alfisols 17%• Ultisols 12%• Vertisols 5%• Alluvial 5%


Structure of Tropical Soils

• Volcanic Best soil structure• Oxisols• Alfisols• Ultisols• Vertisols Worst soil structure


Any Questions?

Documents

Moisture Coldest Warmest month Tropical ClimatesImportant Climate Types for the Tropics • Tropical wet climate –Rain all year round –Short dry season - Monsoon –Winter dry