Global Climate Systems
GPH 111
Local Climate Conditions:
 Monsoon (summer rain)
 Frontal (winter rain)
1. Summer Monsoons
 Monsoon means a “change in the
winds”
 Winds shift from “West” to “East”
 Azores High Pressure moves westward,
driving winds off the Gulf of Mexico and
California into Arizona.
1. Azores High Pressure
1. High Dew Points
 Arizona’s monsoon starts when three
days in a row have dew points 55
degrees or higher.
 Moisture comes from the Gulf of Mexico
and Gulf of California.
 Lifting Mechanisms: Convection,
Orographic, Downdraft
 Need to lift the air to cool it and
generate rain
1. Lifting Mechanisms:
Convection
1. Lifting
Mechanisms:
Orographic
1. Lifting Mechanisms: Orographic
1. Lifting Mechanisms: Downdraft
2. Winter Frontal Systems
 Dominant air masses: Warm Moist to
the south Cold and Dry to the north
 Low pressures from the jet stream spin
counter-clockwise
 This forces the warm moist air over cold
dry air, causing storms
2. Winter Frontal Systems
2. Winter Frontal Systems
2. Winter Frontal Systems
3. Phoenix Climate graph
Major Climate Components:
 Insolation
 Temperature
 Air Pressure
 Wind Belts
 Air Masses
 Precipitation
What controls Temperature
1) Latitude* – Lower latitude warmer and more moderate,
higher latitude cooler and more extreme
2) Continentality* – Close to ocean more moderate, far
from ocean more extreme
The importance of Latitude…
And Continentality…
Where
would you
rather
vacation,
Wichita or
San Diego?
Where coastal regions experience moderate temperatures
compared to locations inland because it is much harder to
change the temperature of water compared to land.
Wet versus Dry…
Reasons for…
Dry seasons
Reasons for…
Wet seasons (Review)
1) High pressure systems*
1) Convergent* – ITCZ
2) Bounded by cool ocean
currents*
2) Convection* – Heating
3) Frontal* – Cold Fronts
Desert Causal Elements:
1) High Pressure Systems
Great Victoria Desert, AU
Desert Causal Elements:
2) Bounded by cool ocean currents
Atacama
Desert, Chile
Climate Classification Categories
 Tropical [A] (tropical latitudes mild year round)
- rain forest (rainy all year)
- monsoon (> 6 months rainy)
- savanna (< 6 months rainy)
 Mesothermal [C] ( subtropics / mid-latitude mild winter)
- humid subtropical (hot summers)
- marine west coast (warm to cool summers)
- Mediterranean (dry summers)
 Microthermal [D] (mid / high latitude cold winter)
- humid
continental (hot to cool summers)
 Deserts [B] (permanent moisture deficits)
- arid deserts (tropical and midlatitude)
Letters
refer to
Koppen
System
Tropical - Rain Forests [Af]
Tropical - Monsoon Climates [Am]
Tropical - Savanna Climates [Aw]
Mesothermal - Humid Subtropical
[Cfa]
(Hot-Summer Climates)
Mesothermal - Marine West
Coast [Cfc]
(southern hemisphere)
Mesothermal –
Mediterranean [Cwb-a]
(dry summer)
Microthermal - Humid
Continental [Dfa-wa]
(hot summer climate)
Desert - Midlatitude
[BWk]
(cool desert climate - arid)
Things to know:
 How do Arizona’s monsoons work to give us
rain in the summer?
 Arizona receives rain from frontal systems in the
winter (already covered this earlier)
 Know the two major components of climate:




temperature and precipitation
The two controls on temperature
Two reasons for a dry season
Three reasons for a wet season
Example locations of the climate classification
categories covered, why they are dry and why they
are wet, and why they have large variations or
little variation in temperature
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