WEATHER SYSTEMS

It dictates how and where we live, but what influences weather?

WHAT INFLUENCES WEATHER?

A range of factors determine the weather we experience from week to week and season to season. As certain areas of the earth tilt away from or towards the sun, this affects how much warmth they receive. When Australia tilts towards the sun, we get summer weather. Winter arrives when we tilt away from the sun. The earth tilts at about 23.5 degrees.

Weather also differs between the northern and southern hemispheres. Weather is similar all year round at the Equator but climates cool the further you move away from the Equator.

Air pressure is a key influence on weather. Our planet has pockets of cool and hot air and when those pockets mix, it creates air pressure and wind.

Water is another major influence. As water evaporates from lakes, oceans and rivers it creates moisture in the atmosphere which creates wetter weather.

WIND AND AIR MASS

Australia has eight major air masses. These are the: Modified Polar Maritime, Southern Maritime, Tropical Maritime Tasman, Tropical Maritime Pacific, Tropical Maritime Indian, Equatorial, Tropical Continental, and Subtropical Continental. They bring cool or warm air, cloud, rainfall, humidity or hot, dry weather.

Trade winds blow in an east to southeasterly direction across the southern hemisphere. As they travel east across the Pacific Ocean, they collect moisture which falls as rain on the east coast. Australia’s wettest place, according to the Bureau of Meteorology, is Mt Bellenden Ker, between Cairns and Innisfail, Queensland, where the average annual rainfall is 7708mm.

OUR OCEANS

Our oceans are part of the earth’s natural heating system. Most of the radiation produced by the sun is absorbed by water and once this heat is trapped, mostly around the Equator, oceans distribute that warmth. Ocean currents take warm water from the Equator towards the north or south poles and those same currents return cold water from the poles to the Equator where water is warmed again. Warm water raises air temperatures above and around it, while cold water has the opposite effect. This never-ending cycle helps regulate the earth’s temperatures. Otherwise, large areas of our planet would be uninhabitable.

THE SUN

The sun produces infra-red radiation that generates heat. This warms the oceans that cover about 75 per cent of the earth’s surface. Oceans circulate that heat and help warm the air. When the sun’s radiation reaches the ground it heats the earth’s surface and that warmth is also dispersed into the atmosphere. The earth avoids getting overheated as some of that warmth is lost to the extreme coldness of outer space. The sun is vital for keeping temperatures stable and warm enough for us to survive.