Weather is the condition of the air on earth at a given place and time- whether it is blowing or calm, dry or wet, warm or cold.
On earth, weather starts with the sun. It produces heat that warms the atmosphere, and leads to:
1. Water evaporation into the air:
As air rises, its temperature drops. As the moisture in the air cools, it condenses into tiny suspended droplets, forming clouds. The droplets inside the clouds become larger a more moisture is evaporated into the air. Eventually, they are too heavy to remain suspended and fall to earth as precipitation - rain, snow, sleet or hail.
2. Air rises
The condition of air and how it acts to create weather primarily is influenced by two things - heat (the sun) and water.
Predicting the Weather
Meteorologists are scientists who monitor weather conditions.
They sample a wide network of weather stations and use satellite images to map out the positions of the large air masses circling the Earth. Since air masses interact in a relatively predictable way, meteorologists are able to predict weather patterns with some degree of accuracy.
Every weather prediction is based on the chance that the weather conditions will act together in a certain way. However, forecasts can be wrong. Some general patterns help meteorologists predict weather for a local area.
Moving weather conditions are due to wind patterns across the earth. In any given place, a clue to tomorrow's weather may be found by looking at the weather of the area to the west.
However, geographic features in your area such as large bodies of water and mountains can affect local weather.
For example, if you live near the Atlantic Ocean, conditions to the east often influence your weather. And whether you live near the east coast or west coast, temperatures near the ocean may be higher than they are even short distances inland.
The heat-holding ability of large bodies of water causes warming of the air along the coast.
In the spring, for example, it's generally warmer in the outlying areas than it is closer to the lake.
People who live on the eastern side of a mountain range have mostly dry weather. Even when moisture-laden air masses move into the area, their interaction with the mountains causes most of the moisture to fall on the western slopes.
So keep in mind that you can not just look at a weather map and expect to make totally accurate predictions. Lots of factors affect what happens in an area on any given day.
For geography, remember these five points:
• In coastal areas, cool air usually blows inland during the day and out to sea at night.
• The air above cities is often warmer than the surrounding area. In certain situations, this can create an artificial low pressure system.
• High altitude areas are usually colder and receive more precipitation than low altitude areas.
• In hilly areas, hot air moves up the slopes during the day and won the slopes at night.
• Coastal areas have more moderate temperatures than inland areas, and are generally warmer in the winter and cooler in the summer.
Tools used for Weather Prediction
a. Barometers: They measure the air pressure, which is sometimes referred to as barometric pressure.
The pressure of the air on the pool of mercury in the barometer causes the mercury to rise in a tube.
Scientists measure the height of mercury in the tube in inches. Therefore, air pressure is often stated in inches of mercury.
More common are anaeroid barometers, which don't contain mercury but have a small box inside instead.
The air pressure on this box causes it to change shape, moving a needle on a gauge that indicates the air pressure. Normal air pressure readings vary from 28 to 31. Quick changes in air pressure often mean a change in the weather is about to occur.
b. Anemometer: Meteorologists use anemometers to measure wind speed, but you can estimate wind speed just by looking around.
Watch how smoke rises in chimneys, how leaves move in trees, and how flags wave in the wind. Sailors and other people sometimes rate their observations of wind speed according to the Beaufort scale.
If you don't have an anemometer to measure wind speeds, you can get a good idea of how fast the wind is blowing just by looking at objects around you.
c. Weather Balloons: They are special balloons that have a weather pack on them that measures temperature, air pressure, wind speed, and wind direction in all the layers of the troposphere.
d. Meteorologists also use Satellites to observe cloud patterns around the world, and radar is used to measure precipitation.
All of this data is then plugged into super computers, which use numerical forecast equations to create forecast models of the atmosphere.
These forecast models can be both correct and incorrect, so meteorologists must be careful and determine whether they agree with the model or not.
If the meteorologists disagree with the model, then they must determine a different outlook for their forecast.
Credit: United States Search and Rescue Task Force, GPB media