Atmospheric Movement in Weather Change

Weather  The short-term (a few hours or days) condition of the atmosphere at a given location. Water and air move constantly- --together they create WEATHER! –The weather of an area is due to four atmospheric factors: heat energy, air pressure, winds, and moisture.  Meteorologists are scientists who study and predict the weather

Weather is the condition of Earth’s atmosphere at a particular time and place.

Composition of the Atmosphere   Other gases: – –Oxygen and nitrogen = 99% of dry air.   Carbon dioxide and argon make up most of the other one percent (1%).   The remaining gases are called trace gases because only small amounts of them are present.

Composition of the Atmosphere   Nitrogen is the most abundant gas in the atmosphere – –Makes up a little more than three fourths of the air we breathe – –Essential to living things   Most living things cannot obtain nitrogen directly from the air – –Bacteria convert nitrogen into substances – –Plants then absorb the nitrates from the soil and use them to make proteins. – –Animals must eat plants or other animals.

Getting Energy All energy on Earth comes from the Sun, but there are three different ways things can get the energy once it is here.

Radiation Radiation – is the absorption of energy. Energy travels from the sun in electromagnetic waves. These waves are absorbed by the things on earth.

(Ground is warmed by radiation) Heat is transferred to the air when the air touches the ground.

The warmer something gets the more energy its molecules have. The more energy molecules have the faster they move. The faster molecules move the more volume (space) they take up.

Basic Ingredients for Weather

The solar radiation heats the surface of the earth. Heat is transferred to air molecules that come in contact with the ground.

As the Hot Air Rises… Cooler air is pulled in from other places Do you know what this is called?

Air Pressure   Properties of Air Air pressure occurs as a result of the weight of the air pressing down on the Earth. A change in air pressure usually indicates a change in weather is going to occur. A body of air that has similar temperature, humidity, and air pressure is called an air mass. There is a column of air above you all the time. The weight of the air in the atmosphere causes air pressure. Air push in all directions—down, up, and sideways

Ground warmed by radiation As the air becomes less dense it rises

Ground warmed by radiation Rising air spreads heat throughout the atmosphere.

Increasing Altitude   Altitude, or elevation, is the distance above sea level, the average level of the surface of the oceans. – –Air pressure decreases as altitude increases.   As air pressure decreases, so does density. Altitude

Units of Air Pressure   Weather reports Most weather reports use inches of mercury. – –National Weather Service maps indicate air pressure in millibars.   x

 An air mass with low pressure is likely to be stormy. An air mass with high pressure is likely to be fair. Air moves from areas of high pressure to areas of low pressure. This movement occurs as the differences in air pressure cause wind.

The Wind   Winds are the result of uneven heating of the Earth’s surface – – This uneven heating causes differences in air pressure to develop.

the transfer of heat through movement in the atmosphere.

Where Does Wind Go?   Winds always blow from areas of high pressure to areas of low pressure. – –The closer wind is to the low pressure area the faster it blows.

Moves pressure systems from West to East. Pacific Ocean Atlantic Ocean Gulf of Mexico

COLD FRONT or WARM FRONT? Air masses are large bodies of air classified by their temperature (warm or cold) and amount of water (wet or dry).

Warm Front

COLD FRONT