The blanket of air around the earth is called the atmosphere. All our weather happens in the bottom layer of the atmosphere called the troposphere, which is six to ten miles thick. Meteorology is the study of the changes in temperature, air pressure, moisture, and wind direction in the troposphere.
The Sun Starts it All
There is one basic reason we have weather, and that is the sun. Weather systems start because the sun's energy heats up some parts of Earth more than others. Most of the time the sun shines most directly on the middle of Earth, with less heating at the north and south poles. Earth is tilted on its axis at exactly the right angle to have seasons, with different parts of Earth being heated more or less during different times of the year. Land heats up faster than water, setting up temperature differences between oceans and continents. This unequal heating creates variations in temperature and air pressure, winds, and ocean currents.
Air Masses and Fronts
The winds move heat from the tropical regions toward the poles in a never-ending effort to reach a temperature balance. In the process, fronts set up between warm and cold air masses and a stream of fast-moving air high up in the sky called the "jet stream" forms. Disturbances develop along the fronts and in the jet stream that trigger centers of low and high air pressure. The fronts and low pressure areas make air rise to form clouds and precipitation.
Earth's Amazing Water
Earth is also unique in that all three forms of water--liquid, solid and gas--exist naturally. Heating from the sun helps evaporate water from the oceans as a source for clouds and precipitation. The sun-powered circulations of evaporation, condensation and precipitation move Earth's water from the oceans to the atmosphere to land and back between these three forms.
What else does the Sun do?
Heating from the sun can also trigger thunderstorms. Clusters of thunderstorms over warm ocean waters can turn into hurricanes. The sun is behind all the changes in our weather, and if the sun were to suddenly go out, our weather machine would stop too.
ęCopyright 2004 Nick Walker/Small Gate Media