What is Weather?

Weather What does it mean? What does it include? Where does it happen? Where does it come from? Where does the energy come from? Who studies weather?

What do you know about meteorology? What tools do meteorologists use in order to do their jobs?

Weather: Instruments and technology OLD STUFF NEW STUFF To the Thermometer – uses the expansion of liquid to measure (air) temperature Barometer - uses the expansion of certain substances to measure air pressure Psychrometer – uses dual thermometers to measure humidity Radio/television – enables the spread of information Radar – uses radio waves to detect things in the atmosphere Computer – stores, organizes and (now) interprets data Satellites – gives current data about the condition of the earth’s atmosphere .-Relays information quickly (communications)

What is the job of a meteorologist? -Observe -Study -Understand -Interpret -Predict How has technology affected meteorology and the people of our planet? -Better information and accuracy -Ability to spread information, educate and warn.

? ? Temperature Density Pressure Knowing what you do about: What can you guess about the movement of air (atmosphere) on our planet? Hint: What are the coldest parts of our planet? What are the warmest parts of our planet? How would air interact between these locations? *In general, and on a large scale, we can safely say that air will move from higher pressure (cold) areas on our planet towards lower pressure (warmer) areas on our planet.

The path that this air takes on our planet is described and shown as “Global Winds”

Because the Earth spins at 1000 mph, the paths of these winds are not straight, but curved. This fact is referred to as: The Coriolis Effect

Air Masses - uniform bodies of air What we know about density tells us that denser air (cold) will sink and less dense air (warmer) will rise. Air Masses - uniform bodies of air An air mass is a large body of air that has similar temperature and moisture properties throughout. The best source regions for air masses are large flat areas where air can be stagnant long enough to take on the characteristics of the surface below.

Jet Stream -current of rapidly moving air Fronts - the boundaries between air masses A front is defined as the transition zone between two air masses of different density. Jet Stream -current of rapidly moving air The jet stream is a current of fast moving air found in the upper levels of the atmosphere. This rapid current is typically thousands of kilometers long, a few hundred kilometers wide, and only a few kilometers thick. Jet streams are usually found somewhere between 10-15 km (6-9 miles) above the earth's surface.

What are the global wind patterns What are the global wind patterns? The equator receives the Sun's direct rays. Here, air is heated and rises, leaving low pressure areas behind. Moving to about thirty degrees north and south of the equator, the warm air from the equator begins to cool and sink. Between thirty degrees latitude and the equator, most of the cooling sinking air moves back to the equator. The rest of the air flows toward the poles. What are the trade winds? The trade winds are just air movements toward the equator. They are warm, steady breezes that blow almost continuously. The Coriolis Effect makes the trade winds appear to be curving to the west, whether they are traveling to the equator from the south or north. What are the doldrums? The doldrums is an area of calm weather. The trade winds coming from the south and the north meet near the equator. These converging trade winds produce general upward winds as they are heated, so there are no steady surface winds.

What are the prevailing westerlies What are the prevailing westerlies? Between thirty and sixty degrees latitude, the winds that move toward the poles appear to curve to the east. Because winds are named from the direction in which they originate, these winds are called prevailing westerlies. Prevailing westerlies in the Northern Hemisphere are responsible for many of the weather movements across the United States and Canada. What are the polar easterlies? At about sixty degrees latitude in both hemispheres, the prevailing westerlies join with the polar easterlies to reduce upward motion. The polar easterlies form when the atmosphere over the poles cools. This cool air then sinks and spreads over the surface. As the air flows away from the poles, it is turned to the west by the Coriolis effect. Again, because these winds begin in the east, they are called easterlies.

What is a sea breeze? On a warm summer day along the coast, this differential heating of land and sea leads to the development of local winds called sea breezes. As air above the land surface is heated by radiation from the Sun, it expands and begins to rise, being lighter than the surrounding air. To replace the rising air, cooler air is drawn in from above the surface of the sea. This is the sea breeze, and can offer a pleasant cooling influence on hot summer afternoons. What is a land breeze? A land breeze occurs at night when the land cools faster than the sea. In this case, it is air above the warmer surface water that is heated and rises, pulling in air from the cooler land surface.