In this lesson, you’ll be learning about weather patterns. We’ll cover the five main components of weather and look at how specific patterns develop, as well as the forces driving weather movement across the world.
What Is a Weather Pattern?
Have you ever noticed how there will be beautiful, sunny weather for days on end, but then one day you wake up and it’s gray and raining? The rain doesn’t always stop within the day either, and sometimes the gloomy days go on just as the sunny days did. When the weather maintains consistency for a period of time it’s called a weather pattern. Changes in weather are important to human life, as it governs our daily activities and brings moisture to nourish agriculture and be consumed. For example, do you need to protect your house from heavy rains or your lawn from dry temperatures that can cause brush fires? More serious weather, like tornados and hurricanes, can cause severe damage to people and properties. Today, we’ll be learning about the different aspects of weather patterns, how they develop, and their movement across the country.
Components of Weather Patterns
There are five main components to weather:
- Air pressure
Temperature is how warm or cool the air is in the atmosphere, while humidity measures how much moisture is present in the atmosphere. Humidity also influences the perceived temperature, and anyone who’s been stuck outside on a humid day can attest to how hot it feels compared to a day at the same temperature with low humidity. The high moisture content in the air prevents the sweat from evaporating off of our skin, which would normally keep us cool.
Air pressure is the amount of air molecules packed into an area. Changes in atmospheric pressure create weather patterns, which we’ll discuss later on. High pressure areas bring calm, cool, sunny weather whereas low pressure areas bring warm weather, rain, and clouds.
Wind is the movement of air through the atmosphere, and it helps to move air from high pressure areas to low pressure areas. Changes in air pressure also bring about clouds, collections of dust, and water vapor in the atmosphere. Precipitation is any form of water falling from the clouds; the most common forms that you may be familiar with are snow and rain. These processes bring changes in temperature and greatly influence human activity.
How Weather Patterns Develop
Now that we know some basics, let’s look at how weather patterns develop. Weather patterns start with air masses, which are large bodies of air with uniform temperatures and air pressure. Air masses are categorized based on the temperature (polar or tropical) and their origin (land or marine). The origins of the air masses influence the humidity of the air.
Cold Front Movement
When two air masses collide, the fronts, or leading edges, create weather patterns like clouds, precipitation, and even tornados. High pressure systems usually bring cooler temperatures, called a cold front. High pressure air is dense because the temperature is lower, pushing the air molecules together and making it sink.
Low pressure air is generally warmer and is known as a warm front. The air molecules are spread further apart, leaving more room for water vapor. It’s also less dense than a high pressure system. When a cold front enters an area, the warm front air is forced upward. As it ascends the temperature decreases and the air condenses. The water molecules are forced out of the air and form clouds, which eventually condense and fall as precipitation. This brings rain and storms to the area.
Warm Front Movement
If a warm front of low pressure moves into a cold front of high pressure, the warm air is forced upwards at an angle. The warm air moves slowly upward, again causing clouds and precipitation to form in the atmosphere. However, the warm front moves more slowly than the cool front, so the rain typically lasts longer than the advancement of a cool front.
Movement of Weather Patterns
Weather patterns typically move from west to east based on a wind pattern called the jet stream. The unique pattern of the jet stream is driven by the rotation of the earth. To understand how it works, let’s imagine the earth didn’t rotate at all. Air at the equator is much warmer than the air at the poles. This hot air rises because it’s less dense, and the cool air from the poles would flow in as the hot air at the equator rises. The hot air would move towards the poles, become cooler, and sink. In this case the jet stream would blow north to south.
However, we know that on earth, the jet stream blows from west to east. The rotation of the earth causes air to flow counterclockwise around low pressure systems, like the warm air at the equator. This drives airflow in a direction from left to right, or west to east. Think of the jet stream like a river of air, moving air masses west to east and transporting weather across the globe.
Weather patterns are long periods of similar weather. Weather patterns are described by five main components:
- Air pressure
Air masses are large bodies of air with different characteristics, depending on their origin and temperature. When a front, or leading edge, of two air masses come together, the warm, lower density air is pushed upward into the atmosphere by the cold air with a higher density. The warm air condenses in the cold, upper atmosphere causing clouds and rain. Air masses are carried around the world by the jet stream, which moves air west to east based on the rotation of the earth.