outline further reading: chapter 10 of the text book - wet tropical climate - coastal trade wind...

Outline

Further Reading: Chapter 10 of the text book

- wet tropical climate

- coastal trade wind climate

- dry tropical climate

Natural Environments: The AtmosphereGE 101 – Spring 2007

Boston University

Myneni L24: Low Latitude Climates

Apr-21-07(1 of 13)

- wet-dry and monsoon climate

Introduction


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Apr-21-07(2 of 13)

• Continuing,

– We want to look at low-latitude climates

– Lie between the tropics of Cancer and Capricorn (about 23S to 23N)

– Tends to be uniformly warm

– Principally differentiated by variations in precipitation

Introduction


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Apr-21-07(3 of 13)

– The circulation in the region is dominated by the Hadley Cell

• ITCZ and tropical low-pressures

• Subtropical Highs

• Easterly trades

– Low variability in temperature

• High temperatures: near equator

• Low seasonality: near equator

– High variability in precipitation

• Humid: ITCZ

• Desert/Arid: Subtropical high

• Strong seasonality between the two as the ITCZ shifts north and south

– Creates 4 main climate regimes

– Wet Equatorial Regime

– Coastal Trade-wind Regime

– Wet-Dry and Monsoon Regime

– Dry Tropical Regime


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Apr-21-07(4 of 13)

ITCZ

Wet Equatorial Climate-1

– Located under the ITCZ from 10N-10S

– Two characteristic air masses (warm and moist)• mT

• mE


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Apr-21-07(5 of 13)

Wet Equatorial Climate-2

– Dominated by uniform temperature and precipitation

– Precipitation is supplied by tropical convection (>250 cm/yr)

– High temperature due to proximity to equator

– Predominant vegetation type is rainforests


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Apr-21-07(6 of 13)

Coastal Trade Wind Climate-1

Trade Winds

Subtropical High

Subtropical High

ITCZSubtropical High

Subtropical High

ITCZ

– Located along narrow belts on the coasts (5-25N)

– Persistent precipitation supplied by orographic lifting as easterlies flow over the coasts

– In addition these regions are strongly influenced by the presence of tropical cyclones


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Apr-21-07(7 of 13)

Coastal Trade Wind Climate-2

– Precipitation influenced by trade-winds

– Temperature is persistently warm, although there is summer seasonality due to changes in insolation

– Also note that there is a break in the precipitation due to the southerly movement of the subtropical high

– Predominant vegetation type is also rainforests


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Apr-21-07(8 of 13)

Wet-Dry and Monsoon Climates-1

HL

LH

– Located between equatorial and subtropics– 5° to 20° N and S in Africa and the Americas, and at 10° to 30° N in Asia – Strongly influenced by the movement of the ITCZ

• Summer: ITCZ moves north and the weather is dominated by convective precipitation and mT, mE air masses

• Winter: ITCZ moves south and the weather is dominated by the sub-tropical high, cT air– Technically, ‘wet-dry’ region is in the continental interior while ‘monsoon’ region is closer to the

coasts


Boston University


Apr-21-07(9 of 13)


– Temperature is persistently warm, although there is summer seasonality due to changes in insolation

– Note the strong seasonality in precipitation• Wet-dry region dominated by precipitation associated with the ITCZ• Monsoon region dominated by precipitation associated with winds coming off the

ocean (hence the relation to coastal wind regime)


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Apr-21-07(10 of 13)


Dominant vegetation type is savanna, open grassland


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Apr-21-07(11 of 13)

Dry Tropical Climate-1

Subtropical High

Subtropical High

– Located poleward of the wet-dry region (15-25N)

– Strongly influenced by the subtropical high

• Associated with the descending limb of the Hadley circulation

• Produces clear sky, warm stable air

– Two subtypes

• Western litteral - west coasts of Africa and S. America where cold-air reinforces the atmospheric stability -> very dry

• Semi-Arid - transition between dry tropical and wet-dry tropics

– Very short rainy season which sometimes doesn’t come for years


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Apr-21-07(12 of 13)

Dry Tropical Climate-2

– Moderate range in temperature due to changes in declination– Persistently low precipitation– Dominant vegetation type is shrubland


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Apr-21-07(13 of 13)

Summary

• Overall there is a fairly simple set of controls

– Temperature is controlled by distance from equator

• Generally warm everywhere

• Higher seasonality as one moves away from the equator

– Precipitation is dominated by 4 factors

• ITCZ - wet equatorial regime

• Sub-tropical high - Dry tropical regime

• Easterly trade winds - trade wind regime

• Seasonal shift in ITCZ - wet-dry and monsoon regime

– Could also define by variability in precipitation

• Low variability - wet equatorial and trade-wind regime

• Moderate variability - wet-dry and monsoon regime

• High variability - dry tropical regime

outline further reading: chapter 10 of the text book - wet tropical climate - coastal trade wind...

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