moisture coldest warmest month tropical climatesimportant climate types for the tropics • tropical...
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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
Tropical Horticulture - Texas A&M University
Koeppen’s Climate Classification
Tropical Horticulture - Texas A&M University
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
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Climates in the Tropics
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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
Tropical Horticulture - Texas A&M University
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
tion
(W/m
2/da
y)
020
Tropical Horticulture - Texas A&M University
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
adia
tion
(W/m
2/da
y)
02040
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
Solar Radiation Drives the Climatic System
• Tropical Region– High consistent levels of incoming
solar energy– 75% of surface as water - thus
much moisture
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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
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Intertropical Convergence Zone
• ITCZ where trade winds converge
Tropic of Cancer - 23.5° N
Tropic of Capricorn - 23.5° S
Equator Intertropical Convergence Zone
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Intertropical Convergence Zone
• ITCZ follows the sun and modified by topography
Equator Intertropical Convergence ZoneJuly
January
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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
Tropical Horticulture - Texas A&M University
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
Intertropical Convergence Zone
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Annual evaporation exceeds annual precipitation
Color codes: Grays and blue = steppe climateShades of orange = desertsYellows = cool dry deserts
Intertropical Convergence Zone
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
Tropical Horticulture - Texas A&M University
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
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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
Tropical Horticulture - Texas A&M University
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
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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
Tropical Horticulture - Texas A&M University
Ultisols in the Tropics
U
U
UU
U
U
U
U
U
U UU
U U U
U
12% of land area
Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
Alfisols in the Tropics
A
A A A
AA
A
A
A A
A
A
A
17% of land area
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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
Tropical Horticulture - Texas A&M University
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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Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
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
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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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Tropical Horticulture - Texas A&M University
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
Tropical Horticulture - Texas A&M University
Vertisols in the Tropics
VV
VV
V
3-5% of land area
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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
Tropical Horticulture - Texas A&M University
Histosols - Peaty soils• Soils with peaty accumulations• Need to be drained before use
• Deep peats, pineapple production• Shallow peats, rubber, oil palm, coffee
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Fertility Levels of Tropical Soils
• Alluvial most fertile• Vertisols• Aridosols• Volcanic• Alfisols• Ultisols• Oxisols least fertile
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Tropical Horticulture - Texas A&M University
Extent of Tropical Soils
• Oxisols 25%• Aridisols 20%• Alfisols 17%• Ultisols 12%• Vertisols 5%• Alluvial 5%
Tropical Horticulture - Texas A&M University
Structure of Tropical Soils
• Volcanic Best soil structure• Oxisols• Alfisols• Ultisols• Vertisols Worst soil structure
Tropical Horticulture - Texas A&M University
Any Questions?