Latitude and Longitude
Australia is a diverse continent. The reason for this diversity is that the continent is spread
across almost 33o in latitudinal measurement. Nearly 40 percent of the continent is in the
tropical climate zone while the other 60 percent is in the temperate climate zone. Both of
these zones have widely varying climate types, from arid deserts to tropical rainforests.
Latitude and climate
Latitude is an important factor in the distinction between climate zones. Temperature,
precipitation and the circulation of wind and water through our environment give the earth a
vast diversity of climate types. Cold and warm climates are continuously cycled though the
atmosphere and the hydrosphere so that one place does not experience extreme heat or
extreme cold all of the time.
What is latitude?
Latitude is the distance to any point on the globe in relation to the equator. Latitude is
measured in degrees at any point north or south of the equator. Imaginary lines run east - west
around the globe, all parallel to the equator. These are the parallels of latitude.
The equator measures 0o latitude. One degree of latitude is equal to about 110 kilometres.
Degrees are split into smaller measurements of minutes, with 60 minutes (60') equal to 1
degree (1o).
The North Pole is 90o north and the South Pole is 90o south. All measurements in between the
equator and the poles are within 0o to 90o and are either north (N) or south (S). The equator
divides the globe into the northern hemisphere and the southern hemisphere.
Regions of latitude
There are four different parallels of latitude that separate the Earth into sections based upon
the amount of insolation (solar radiation) that is received:
1. The Tropic of Cancer at 23
solar radiation.
o
1. The Tropic of Capricorn at 23
direct solar radiation.
N (23o 30' N) marks the northern most spot of direct
o
S (23o 30' S) marks the southern most spot of
1. The Arctic Circle at 66 oN (66o 30' N) marks the northern most spot where the sun
still appears every day. North of this circle is where the sun shines for 24 hours at a
time in the summer and does not shine for 24 hours at a time in the winter.
1. The Antarctic Circle at 66 oS (66o 30' S) marks the southern most spot where the
sun still appears every day. South of this circle is where the sun shines for 24 hours at
a time in the summer and does not shine for 24 hours at a time in the winter.
What is climate?
Climate is the study of weather over time. Weather is the short-term study of temperature,
precipitation rates, humidity, sun and wind. There are several important factors that influence
the type of climate in any given area:
1.
2.
3.
4.
5.
latitude and solar radiation
precipitation and water stores
global circulations of air
topography and altitude
ocean currents
Climate zones
Based on latitude and solar radiation, the Earth can be divided into three main areas of
climate types:
1. Tropics - between the Tropic of Cancer and the Tropic of Capricorn; warm/hot
2. Temperate - north and south of the tropic lines to the Arctic Circles; warm and cool
3. Polar or Arctic - north and south of the Arctic and Antarctic Circles; cold
Regions within climate zones
These three zones can be further divided into different climate regions based upon the
seasonal temperatures, precipitation rates, altitude and topography, distance from oceans and
atmospheric circulations. Throughout the years many lists have been composed to further
classify the regions of the world. Most of these lists are based upon that of Wladimir Koppen.
His list separates the world into five climatic regions:
1.
2.
3.
4.
5.
Tropical - warm and wet
Arid - dry desert
Warm Temperate - warm wet and dry seasons
Cool Temperate - cool wet and dry seasons
Polar - cold
Within these five categories there are further ways to distinguish between the climatic areas
of the world. Some tropical areas are humid year round. Others areas are marked by a dry
season during winter, such as the northern coasts of Australia. The tundra can be considered a
polar climate but because of the lack of moisture it could also be considered a cold desert.
Latitude and solar radiation
Latitude affects global climate because different lines of latitude receive different amounts of
insolation.
Solar radiation plays a significant role in the humidity of climates. Areas near ample
quantities of water that receive a large amount of direct solar radiation will have more humid
climates. Warmer climates near water have more evaporation because heated water
evaporates and warm air holds less water vapour than cold air. Thus, condensation and
precipitation occur. Areas in the tropics have higher humidity than the equator and the poles.
Convergent areas occur in the lower latitudes generally between 7ºS and 12ºN (around the
equator) and in the high latitudes north of 37ºN and south of 40ºS (near the poles).
Evaporation < Precipitation = Convergent
Divergent areas occur in the middle latitudes generally between 12ºN to 37ºN in the northern
hemisphere and 7ºS to 40ºS in the southern hemisphere.
Evaporation > Precipitation = Divergent
Seasons
Seasons occur because the tilt of the Earth affects the amount of solar radiation we receive.
Our globe does not sit straight up on its vertical axis. Instead, it is tilted 23º30' from the
vertical.
The Earth is on a yearly orbit around the sun of about 365 days. Because the tilt of the Earth
does not change, the angle of solar radiation at certain points on the Earth will change during
the yearly orbit. When solar radiation hits the southern hemisphere more directly than the
northern hemisphere, it is summer in Australia. When the solar radiation hits the northern
hemisphere more directly than the southern hemisphere, it is winter in Australia.
Air circulations
The circulation of air throughout the world is very important because it stops the equatorial
area from becoming too hot and the polar regions from becoming too cold. The temperature
of the air dictates whether a region is humid or dry, hot or cold.
Air masses are large areas of air that are very similar in their temperature and humidity.
These air masses are linked to the global wind patterns. Atmospheric circulation is controlled
by six regions of winds across the globe and three major pressure cells.
The constant movement of air masses changes air temperature and pressure with latitude and
altitude. Changes in temperature and pressure create different patterns of weather. Areas of
low pressure often create condensation and result in storms. Areas of high pressure often
create clear skies and warm, dry air.
Topography and altitude
Mount Everest is the tallest mountain in the world. The altitude of this giant mountain is
8850 metres. Even though it is located just north of the Tropic of Cancer, Mount Everest has
year-round snowfall and extreme weather conditions. This is because the peaks of the
Himalayan Mountain Range stretch high into the atmosphere.
Temperature decreases with increasing altitude. This is called the lapse rate. Temperatures
usually fall about 2º to 3ºC for every 300 metres of altitude. Low, flat areas will be warmer
than high, mountainous regions of the same latitude. So although the Himalayan Mountain
Range is located along the Tropic of Cancer, the mountains are covered with snow.
Landforms, such as mountains, act as barriers that force air masses to move up and over
them. When warm, moist air meets a mountain it is forced to rise. As this warm air rises, it
begins to cool down with increased altitude and condensation occurs. Once the air is
saturated, precipitation occurs. The rain or snow released on the windward side (the side
from which the wind is blowing) of the mountain is known as orographic rainfall.
After the precipitation, the air mass is dry and flows down the opposite side of the mountain.
This dry air heats up as it descends down the leeward side (the side shielded from the wind)
of the mountain. This is called a rain shadow effect. It is on this side of mountains that
desert climates are often found.
Smaller mountains, hills and slopes are affected by solar radiation. The side of a slope that
faces the sun will generally be warmer and drier than the side that does not. This is called
aspect. A wide, open valley is heated by the morning sun and as the air is heated, it rises. The
rise of warm air draws in cooler air sliding down the side of the valleys. A low pressure area
and upslope winds are created.
Ocean currents
The oceans make up about 70 percent of the Earth's surface. These huge bodies of water
absorb solar radiation and store it on the surface. Oceans heat up and cool down more slowly
than the land, so areas near oceans experience a more stable climate than those further inland.
Places that are not near an ocean or other large body of water, such as central
Australia, experience an arid climate with varying temperatures.
As a result of the daily heating and cooling of the oceans and the land along the coastlines,
wind patterns occur. A sea breeze occurs during the day because the land surface heats up
faster than the ocean surface. The rising air is drawn in by the cooler air over the
water, creating an onshore wind. A land breeze occurs at night because the land surface
cools down more quickly than the ocean surface. The warm air rising from the ocean draws
in the cooler air over the land and creates an offshore wind.
Oceanic surface currents transport water around the globe. These giant surface water
rotations are called gyres and are affected by the Coriolis effect. There is a major gyre in
every major ocean. Water is warmed at the equator and travels toward the poles, distributing
heat. Once at the poles, water is cooled and then travels back to the equator. Where there are
cold currents, the coastal climate is dry. Where the currents are warm, the coastal climate is
moist because of higher evaporation rates.