k-5 geosource

Why is the weather different in high and low-pressure areas?

Why is the weather in high-pressure areas usually fair? Why is the weather in low-pressures areas usually cloudy and stormy? Most weather maps show areas, labeled with an H, where the atmospheric pressure is relatively high, and areas labeled with an L where the atmospheric pressure is relatively low. The isobars around such areas are closed curves with the approximate shape of circles. High-pressure areas are places where the atmosphere is relatively thick. Winds blow outward from these areas, although in a spiraling way.

What is atmospheric pressure?

Air has weight. That idea might seem strange to you, because air seems very thin, even at sea level. Remember however, that the atmosphere extends to great altitudes. The pressure of the air is equal to the weight of a column of air above a unit area on the land surface. The column of air above a square area that is one foot on a side is about 2,116 lb., at sea level. In the metric system, that's about 10,332 kg per square meter. If you try to pump the air out of a closed container, the container will collapse inward from the outside air pressure, unless it is very strong.

What are weather reports?

Weather reports vary a lot in how much information they contain. The simplest and shortest weather report contains only one piece of information: the present temperature. This is the type of report you often hear on the radio. More detailed weather reports also contain information about precipitation, wind speed and direction, relative humidity, atmospheric pressure, and other things as well.

How is rain formed?

Raindrops are formed when the cloud droplets grow big enough to fall out of the clouds. Most of the rain that falls in the winter, and even a lot of it that falls in the summer, is from melting of snowflakes as they fall through warmer air.

How are clouds formed?

Clouds are formed when moist air rises upward. As the air rises, it becomes colder. Eventually the air can't hold all of the water vapor in it, and some of the water vapor condenses to form tiny water droplets. When moist air is cooled at the ground, fog is formed in the same way.

How can we measure the wind?

The wind blows because air pressure is higher in one place than in another place. The air moves from areas of higher pressure to areas of lower pressure. Objects like buildings, trees, and hills affect the direction of the wind near the surface. To get the best idea of the wind direction, try to stand far away from such objects. A park or a playing field is the best place to observe the wind.

How do we measure air temperature?

Air consists of gas molecules, which are combinations of two or more atoms. Although you cannot see them with your eyes, the molecules are constantly moving this way and that at very high speeds. As they move, they collide with one another and with solid surfaces. The temperature of the air is a measure of how quickly the molecules are moving. The more energy of motion the molecules have, the higher the temperature you feel in the air.

What are weather observations?

All sciences begin with observations. Without observations, scientists have no way to develop new theories and to test existing theories. The weather is no exception. Meteorologists (scientists who study the weather) observe many elements of the weather, both at the Earth's surface and at high altitudes. Weather observations are used for predicting the weather and for developing and testing new theories about how the weather works.


Weather is the state of the atmosphere from day to day. It includes temperature, atmospheric pressure, clouds, wind, and precipitation.


Subscribe to RSS - k-5 geosource