Aim: Why does air move?

Transcription

1 Notepack 35 Aim: Why does air move? Do now: What type of pressure would you expect inside a hurricane? High or Low Pressure

2 What is Air Pressure? Air is made up of atoms (oxygen, carbon, nitrogen). Atoms have weight (extremely little weight) Because the atmosphere is thick, there is a lot of atoms between the ground and space. The weight of the air directly above the ground to the edge of space is known as air pressure. On average this weight is about 14.7 pounds per square inch or one ATM (atmosphere).

3 What is Wind? Wind is the movement of air from one area to another. Wind can be spermatic, like a breeze; or it can be uniformed and unidirectional, like the Jet Stream. Wind and move in a straight line or in a circular matter.

4 What does we use to Measure Wind? To measure the direction of wind we use a wind vane. The direction of wind is always the direction in which the wind is coming from. To measure wind spend, we use an anemometer.

5 Factors Causing Wind Earth s Rotation As the Earth rotates, the moving ground is pulling the air above it. This friction between the Earth and the atmosphere creates air currents that move from west to east. Most of the major jet stream (high altitude air currents) run west to east.

6 Factors Causing Wind Earth s Convection Currents Because the Earth is round and on a tilt, Earth s surface do not heat up evenly. Areas where the air heats up, the air is less dense causing it to rise. As this air cools, it becomes more dense. This movement of air rising and sinking creates convection currents. The winds that are created are called trade winds and these winds are constant.

7 Factors Causing Wind Uneven Surface Heating Surfaces that are hot tend to heat the air that s above it. This warm air rises creating low air pressure. Surfaces that are cold tend to cool the air that s above it. This cool air sinks creating high air pressure. This change in air pressure creates wind. Air tends to move from an area of high pressure to an area of low. High Pressure Low Pressure

8 IMPORTANT!!! PUT IN NOTES!!! I FORGOT When there is a high pressure area and a low pressure area in the northern hemisphere The air moves out from the high pressure system (H) in a clockwise direction. The air moves in from the low pressure system (L) in a counter clockwise direction. H L

9 Why is measuring air pressure important? As the air pressure rises, the better the weather will be. As the air pressure drops, the worse the weather will be.

10 Coastal Breezes At the coast there are 2 large masses, the land and the water. The land and the water have different specific heats, which means that they both absorb and radiate heat differently.

11 Coastal Breezes In the daytime, both the ocean and the land are absorbing heat from the Sun. Because the land has a low specific heat than the water, the land heats up faster than the water. This causes the air above the land to also heat up. Warm air rises creating low pressure. Because the air above the water is cooler, it is also heavier (high pressure) The high pressure air always moves towards the low pressure, which means that there is a breeze from the ocean to the land in the daytime.

12 The water heats up slowly because it has a high specific heat The sand heats up fast because it has a low specific heat

13 The Land Breeze In the nighttime, both the ocean and the land radiate (giving off) heat. Because the land has a low specific heat than the water, the land cools faster than the water. This causes the air above the land too also cool down. But because water has a high specific heat, it takes a longer time for the water to cool. Because the air above the water remains warmer than the land air, the ocean air rises (low pressure) The high pressure air from the land moves to low pressure of the water causing a breeze from the land to the ocean in the nighttime.

14 The water cools down slowly because it has a high specific heat The sand cools down quickly because it has a low specific heat