further reading: chapter 11 of the text book outline dry...

Outline

Further Reading: Chapter 11 of the text book

- dry and moist subtropical climate regimes

- mediterranean regimes

- dry mid-latitude and moist continental regimes

Natural Environments: The AtmosphereGG 101 – Spring 2004

Boston University

MyneniL26: Mid Latitude Climates

Apr-02-04(1 of 16)

- marine west coast regimes

Introduction


Boston University


Apr-02-04(2 of 16)

• Previously,– We looked at low-latitude climates– Tend to be uniformly warm– Principally differentiated by variations in precipitation

• Today,– We want to look at mid-latitude climates– As opposed to low-latitude climates these climate regimes are differentiated

by their temperature characteristics as well as their precipitationcharacteristics

Mid Latitude Climatic Regimes


Boston University


Apr-02-04(3 of 16)

– Climates located between 25-55N, mostly in the Northern Hemisphere -> not much land mass in these latitudes in the SH

– Influenced by• Pressure and wind systems

– Northern zone of subtropical high– Polar front

• Synoptic changes in Air Masses and fronts– mT, mP, cP– Travelling cyclones

• Strong seasonality in insolation• Seasonality in pressure systems

– Land-sea temperature differences– Cyclone formation and movement

– Produces 6 different climate regimes

1. Dry Subtropical Regime2. Moist Subtropical Regime3. Mediterranean Regime4. Marine West Coast Regime5. Dry Mid-latitude6. Moist Continental

Dry Subtropical Climates-1


Boston University


Apr-02-04(4 of 16)

Subtropical High

Subtropical High

– Pole-ward extension of Dry Tropical regime (25-35N) with slightly higher seasonality in temperature and precipitation

Dry Subtropical Climates-2


Boston University


Apr-02-04(5 of 16)

– Seasonality in temperature due to changes in insolation– There is also some seasonality in precipitation due to the wintertime influence

of midlatitude cyclones– Vegetation consists typically of drought-resistant species such as cactus

Moist Subtropical Climates-1


Boston University


Apr-02-04(6 of 16)

H

Jet Stream

– Eastern subtropical regions– Have consistent high humidity due to mT air from the western edge of the subtropical

high– In the summer there is also the influence of tropical cyclones

Moist Subtropical Climates-2


Boston University


Apr-02-04(7 of 16)

– Seasonality in temperature due to changes in insolation - typically hot summers with convective precipitation; winters are cooler with the occasional incursion of cP air which leads to freezes

– Precipitation due mainly to convective activity in the summer with precipitation from midlatitude cyclones in the winter

– Vegetation is adapted to lots of water, such as mangrove swamps, etc.

Mediterranean Climates-1


Boston University


Apr-02-04(8 of 16)

H

Jet Stream

H

Jet Stream

– West coast of continents between dry subtropical and marine west coast– In the summer, the region is under the influence of the subtropical high -> dry, clear, warm;

influencd by mT, cT air– In winter, the subtropical high moves south, region receives incursions of mP air, midlatitude

cyclones which brings precipitation

Mediterranean Climates-2


Boston University


Apr-02-04(9 of 16)

• Temperatures are typically mild throughout the year due to the influence of the ocean, low latitudes (compared with other mid-latitude regions)

• Vegetation typically is drought resistant, also usually fire-adapted

Maritime West Coast Climates-1


Boston University


Apr-02-04(10 of 16)

H

Jet StreamH

– West coast of continents at higher latitudes– Fairly persistent precipitation all year long

• In winter, region is affected by mid-latitude cyclones• In the summer, circulation around the subtropical high results in orographic lifting as

westerlies move on shore

Maritime West Coast Climates-2


Boston University


Apr-02-04(11 of 16)

– Temperatures are typically mild throughout the year due to the influence of the ocean, low latitudes (compared with other mid-latitude regions)

– Regions of high productivity– Dense forests in North America (old growth rainforests)– Agricultural centers of Europe

Dry Mid-latitude Climates-1


Boston University


Apr-02-04(12 of 16)

cT

cP– Continental interiors at mid-latitudes– Low annual precipitation

• Westerlies flow over mountain ranges, producing strong rainshadows

• In N. American, region stretches from the Great Basin to the Great Plains

– Strong seasonality in temperature• Due to changes in insolation• Also due to influence of continental air-masses

– Winter: cold, dry air associated with cP– Summer: hot, dry air associated with cT

Dry Mid-latitude Climates-2


Boston University


Apr-02-04(13 of 16)

– Any precipitation they do get is from passing midlatitude cyclones– Vegetation is transitional between desert and forest -> grasslands

Moist Continental Climates-1


Boston University


Apr-02-04(14 of 16)

cP

mTH

– Central and eastern portions of the continents– Strong seasonality in temperature

• Due to changes in insolation• Also due to influence of continental air-masses

– Winter: cold, dry air associated with cP– Summer: hot, moist air associated with mT

– Typically high precipitation all year long, although variable from day to day

• Summer: rain associated with warm, moist mT air (usually also associated with passing fronts)

• Winter: rain associated with mid-latitude cyclones

Moist Continental Climates-2


Boston University


Apr-02-04(15 of 16)

– Note that precipitation decreases in the winter -> due to the fact that the cP air has less moisture in it

– Ample water supply -> forests

Summary


Boston University


Apr-02-04(16 of 16)

• Climate dominated by several factors– Latitude -> determines seasonality in temperature, precipitation– Continental v. marine

• Seasonality in temperature• Availability of moisture

– East coast v. west coast• Interaction of the prevailing winds with land masses• Impact of circulation around the subtropical highs

– Topography• Creates orographic lifting, rainshadows

further reading: chapter 11 of the text book outline dry...

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