STEMScopedia: Weather vs. Climate PDF

# STEMScopedia: WEATHER VS. CLIMATE ## 6.E 7.6 ### Reflect Have you ever heard Florida referred to as the “Sunshine State”? When it comes to natural resources, the Sun shining on our state is one of the most important ones we have. You may have noticed in your time living here that, even on days...

# STEMScopedia: WEATHER VS. CLIMATE ## 6.E 7.6 ### Reflect Have you ever heard Florida referred to as the “Sunshine State”? When it comes to natural resources, the Sun shining on our state is one of the most important ones we have. You may have noticed in your time living here that, even on days when rain falls, most of the time there is also part of the day that is also sunny. ### The Sun and the Weather No matter if you are in the “Sunshine State” or somewhere else, the Sun is the most important factor that causes weather. However, it is not just how the Sun shines in a particular area that causes the weather. That is part of it, but how the Sun’s rays hit the planet all across the globe also matters a great deal. We get two types of energy from the Sun’s rays: light and heat. While the light is important for processes such as photosynthesis, the heat is absorbed by both the land and the surface of various bodies of water. When heat is absorbed by these surfaces, it causes them to heat up. This heat absorption is what ultimately causes weather. When Earth’s surface heats up, the air above that surface is warmed by the heat coming off the surface. When air masses heat up, the molecules that make up that mass move farther apart. When they are farther apart and the ones above them are not (because they have not been heated by Earth’s surface), they rise, and the ones above them sink to be closer to the surface of Earth. This movement of molecules is called convection. It happens to liquids and gases as they are heated. If the heat comes from one direction into the mass, the molecules on that side move apart and are less dense. They then push away from the heat as the expansion happens. The heated part ultimately moves away from the heat source and is replaced by more dense molecules, as in the picture of the pan of water on the right. The hotter water moves toward the top of the pan, and the cooler water replaces it. The same thing happens in an air mass, shown on the right the picture. The movement of these air masses is what causes weather. - **weather** - day-to-day patterns of temperature, moisture, precipitation, and winds The clouds in the sky change with the weather patterns an area experiences. - Convection - Energy is transferred by the mass motion of molecules. ### What Is Weather? All the changes in temperature that, in turn, cause changes in pressure of air masses, evaporation from bodies of water, and condensation in the atmosphere, together are the cause of weather. Rain, sunshine, wind, sleet, and snow are all different types of weather. Weather can even be severe, in the form of tornadoes, hurricanes, and hailstorms. ### The Jet Stream There is a band of high-speed winds fairly high up in the atmosphere, called the jet stream. These winds travel around the globe a few miles above the surface of Earth, but they do not travel exactly in a straight line. Because of the impact of continents and oceans on how air moves upward toward the jet streams, they have a somewhat wavy pattern. Depending on conditions they encounter, they sort of “wiggle” around the planet. The jet stream causes large-scale wind movement and pushes big air masses around. Cold ones and warm ones often bump into each other because of the convection currents that drive these wind bands. - There is one jet stream that affects most of the weather patterns in the United States. Weather is generated when different types of air masses bump into each other. Just like air hovering over your driveway or the movement of water molecules in a pan of water you are heating up, cooler, denser groups of molecules push warmer, less dense groups of molecules out of the way. However, the way those air masses are able to push each other around is affected by where land exists, where mountains are on that land, the location of rivers and the ocean, and many other smaller factors. This is what causes rain, thunder, and even major weather events such as hurricanes. - Clouds form and are moved around because of convection currents and the differences in temperatures of those air masses. ### What Do You Think? Do you think there is a difference between weather and climate? If so, what do you think the differences are? As we just learned, weather is the day-to-day pattern of temperature, moisture, precipitation, and winds. Climate, on the other hand, is the long-term pattern of weather in an area. ### What is Climate? Throughout each year, Floridians expect the temperature to not change too much. Depending on where you live in the state, the lowest temperatures might be a little below freezing, or the weather may rarely get that cold. The highest temperatures are usually not much beyond the mid-90s. In other parts of the United States, the differences in low and high temperatures experienced during the year are often much further apart. Usually, it is the low temperatures that get quite a bit lower. In Florida, we experience a tropical to subtropical climate. This is because we receive more direct rays of the Sun than most of the rest of the United States, since we are closer to the equator. This is why we have fairly moderate weather year-round, with less temperature variation than that of most other places in the United States. Also, precipitation in Florida usually falls as rain, because temperatures often do not dip below freezing. Due to its tropical and subtropical climate, precipitation usually falls during the summer months in Florida. The winter and spring months are often quite dry. - The temperatures in Florida throughout the year do not change as much as they do in other parts of the United States. ### Look Out ### Warm Fronts and Cold Fronts Have you ever heard the weatherman mention warm fronts or cold fronts when he is describing the weather? You may think that this refers to the type of weather coming, in that a warm front means warmer weather is coming and a cold front means colder weather is coming. However, this is not necessarily true. The names of these fronts describe the air mass more than the type of weather you will get when they are in your area. What the names do tell you about is the density of the air in the masses. Cold fronts have air that is denser than what surrounds them, and warm fronts have air that is less dense than what surrounds them. ### What Do You Know? > In your own words, explain the difference between weather and climate. Be as specific as possible, and provide details.