2. What is Weather? What is the Water Cycle? What is Atmosphere? How do weather balloons work? I take you to the next slide! I take you back a slide!

3. What is the Water Cycle?

4. Condensation and Clouds Water vapor in the air gets cold and changes back into liquid, forming clouds. This is called condensation. You can see the same sort of thing at home... pour a glass of cold water on a hot day and watch what happens. Water forms on the outside of the glass. That water didn't somehow leak through the glass! It actually came from the air. Water vapor in the warm air, turns back into liquid when it touches the cold glass.

5. Evaporation Evaporation is when the sun heats up water in rivers or lakes or the ocean and turns it into vapor or steam. The water vapor or steam leaves the river, lake or ocean and goes into the air.

6. Precipitation Precipitation occurs when so much water has condensed that the air cannot hold it anymore. The clouds get heavy and water falls back to the earth in the form of rain, hail, sleet or snow.

7. What is Atmosphere? The Earth's atmosphere consists, from the ground up, of the troposphere, stratosphere, mesosphere, thermosphere, and also the magnetosphere. For now, we will only be concerned with the troposphere which is where weather occurs.

8. What is Atmosphere cont…? The atmosphere of Earth is made up of three primary gases, oxygen, nitrogen, and argon. In addition to these three gases, there are many other gases in the atmosphere, in trace amounts. Additionally there are small particles, or particulates floating in the atmosphere, such as dust, water, and pollen. (allergens!)

9. Atmosphere Experiment!

10. So what if… Like any recipe the balance between amounts of gas in the atmosphere is very delicate. Take for example, Oxygen. Our atmosphere is comprised of precisely 21% oxygen. Any more and our atmosphere would be incredibly unstable and flammable. Any less and all animals would die off because they couldn’t breathe!

11. Weather The weather is all around us, all the time. It is an important part of our lives and one that we cannot control. Instead the weather often controls how and where we live, what we do, what we wear and what we eat. Someone who studies the weather is called a meteorologist. Weather predictions are made by forecasters who you see on television.

12. Meterologist Jargon BAROMETRIC PRESSURE The pressure exerted by the atmosphere at a given point. Its measurement can be expressed in several ways. Hi An area of relative pressure maximum that has diverging winds and a rotation opposite to the earth's rotation Lo An area of a relative pressure minimum that has converging winds and rotates in the same direction as the earth.

13. How do weather balloons work? Twice a day, every day of the year, weather balloons are released simultaneously from almost 900 locations worldwide! Weather balloons, which are made of latex or synthetic rubber (neoprene), are filled with either hydrogen or helium.

14. How do weather balloons work? An instrument called a radiosonde is attached to the balloon to measure pressure, temperature and relative humidity as it ascends up into the atmosphere. By tracking the position of the radiosonde, we can also calculate wind speed and wind direction.