It needs to be remembered that virtually all climate and weather on this planet comes from the sun. The earth does possess an internal energy source, and this can have an effect on weather patterns too, however the amount of energy contained within the planet is tiny in comparison to the amount received from solar radiation. Understanding that most of our weather is driven by the sun is the first step in understanding how the sun affects weather patterns on Earth.
The sun produces radiation in nearly every known band, from sound to gamma radiation. In the case of weather, the most important radiation is infrared. Infrared radiation is the kind of radiation that produces heat, and is what makes a stovetop or a heating element glow as it becomes hotter. This radiation prevents the earth from being a frozen, ice-covered ball of rock.
This part is easy, as has already been mentioned. The weather is a little more complex, yet not nearly as much as many people would try to say it is, at least in essence.
As it moves around the sun, our world is tilted at about 23.5 degrees. This means that in one hemisphere, more sunlight and heat is being received at any given time than in the other hemisphere (the exceptions are the equinoxes, when sunlight is nearly equal between hemispheres.) It also means that heat is greatest, year round, at the equator. It is least at the poles.
Oceans cover three forths of the earth’s surface, and it happens that water is a very efficient carrier of heat and cold. Cold water is dense, and warm water isn’t, so the heat usually stays at the surface while the cold sinks to the bottom of the ocean. At the same time, dense water flows to take the place of water that isn’t as dense. The oceans, in this way, act as a giant temperature regulator, carrying warm water toward the poles and colder water toward the equator.
When the sun heats the water, the water in turn heats the air. Air isn’t quite as efficient at carrying heat and cold, and it isn’t as stable. However, this is where the major weather comes from; the circulation of ocean and air currents due to the heating caused by the sun or cooling caused by the lack of sunlight and radiation. It is also this uneven heating, which causes winds, for exactly the same reason. Hot air rises, cool air rushes in to take its place.
The sunlight and radiation cause weather on a more local level, too. Thunderstorms form when the surface is heated, usually abruptly. The moisture-laden air is pushed high into the atmosphere because of its much lower density, while cold air rushes in behind it. The rapidly ascending column of air is cooled and water condenses, but since more air has been heated and pushes up from beneath, the column grows higher and higher.
It should also be pointed out that we do not fully understand some of the ways the sun impacts the weather, though we can notice the affects. For instance, several centuries ago, the sun went through a quiet period when there were no sunspots. While there are only theories about why this would change weather on Earth, there is little doubt that during this time the global temperatures were substantially colder. This earned the period the nickname of the Little Ice Age, and as seen above, temperatures impact weather patterns.
All of this is made possible because of the sun. Since the earth produces relatively little heat of its own, especially in comparison to the amount of heat received from the sun, without the radiation of the sun, there would be next to no weather. The sun not only has a direct affect on the weather, it is also responsible for the weather to begin with.
When it comes to weather patterns, though it is more complex than presented here, the sun provides the driving force. This is a good thing. Some weather can be devastating, but if not for weather, we wouldn’t get the rain, snow, and winds necessary for everything to grow and to circulate on this planet.