12-8-10 What is weather?

1. 12-8-10What is weather? Do Now: How do you define weather? How do you describe weather? List all possible ways the earth’s atmosphere is heated. HW – R&H pp. 126-127, A&E #1-7

2. 1-10-11Topic 7 Review • Do Now: • 1. Why is it hot and humid at the equator, whereas it is hot and dry at 30 deg. North and south? • 2. Use the diagram on the board and make a 1,3, and 5 day prediction for location A. • HW- Study all of T.7 for exam tomorrow.

3. Weather variables- the details we use to describe weather. • Temperature – average kinetic energy of molecules in air. • Air pressure- the weight of air pushing down on earth’s surface (warm air=low pressure) • Wind – horizontal movement of air (blows from high to low pressure • Humidity- amt. of water vapor in air • Cloud cover- % of sky covered with clouds • Precipitation- rain, sleet, hail, or snow • Storms- rain, blizzard, tornado, hurricane

4. 12-9-10What causes wind? • Do Now: R&H pp. 128-129. • 1. What affect does temperature have on air pressure and why? • 2. What affect does humidity have on air pressure and why? • 3. As altitude increases, what happens to temperature, air pressure, and air density? • HW: R&H pp. 131-132, A&E #8-24

5. 12-10-10What is a wind belt? • Do Now: • 1. If the barometer is falling what kind of prediction would you make (temp, humidity, cloud cover, chance of precipitation)? • 2. What causes wind? • 3. Look at p.129. Use the top right Pressure chart and convert 30.10 inches to millibars. • HW- R&H pp. 133-135, A&E# 25-35.

6. Wind- the horizontal movement of air. • Caused by uneven heating, causing changes in temperature. • Uneven temp. causes changes in air pressure, creating areas of higher and lower pressure. • Air or wind blows from regions of high pressure to regions of low pressure, always named from where it comes from. • * Can happen locally with land and sea breezes or globally with wind belts. The greater the pressure gradient the greater the wind speed. No change in pressure results in no wind.

7. 12-13-10What causes ocean currents? • Do Now: • 1. How does weather travel in the United States? • 2. What is the jet stream? • 3. Why do deserts form at 30 degrees latitude? • 4. What causes ocean currents? • HW- Finish Lab

8. Ocean Currents

9. 12-14-10How do clouds form? • Do Now: • 1. Describe all the factors that affect evaporation. (p.138) • HW: Get weather readings

10. Humidity Temperature and Dew Point 1. Humidity – water vapor in the air • A. Absolute humidity – actually how much water vapor is in the air in grams/m3 • B. Relative Humidity- the amount of water vapor the air is holding compared to what it could hold at a specific temperature, expressed as a %. Warmer air can hold more water vapor than cool air. • Dew Point Temperature- the temp. at which air becomes saturated or full with water vapor, meaning R.H. is 100%. Directions on p.139 for determining dew point. ** If air temp. drops below the dew pt. water vapor will have to condense.

11. Steps to Cloud Formation Clouds form Where moist air Rises Expands and cools. RAEC- rising air expands and cools.

12. Steps to Cloud Formation • Rising humid air expands and cools (RAEC) • When the air cools to the Dew Point temp. the R.H. will become 100% meaning air is saturated. • Condensation will now occur as long as there is a condensation nuclei available (ex. Dust, smoke, pollution) as a surface for condensation to form on. A cloud is born. • Very fine cloud droplets will collide and become larger, eventually becoming too heavy to be supported by the cloud and will fall from the sky as precipitation.

13. Cloud Types Cumulus- white, puffy, cotton ball, fair weather clouds. Stratus – long, thin clouds that cover large portions of the sky. Hard to differentiate where one cloud ends and another one starts. Alto- higher up in atmosphere Cirro/Cirrus Very high up in atmosphere. Called mare’s tails and they predict rain is coming. Nimbo/Nimbus- thunderstorm version.

14. 12-16-10How does precipitation form? • Do Now: • 1. What are the steps to cloud formaton? • 2. What does precipitation do for the atmosphere, explain? • HW- Get weather readings, finish lab.

15. 12-17-10Aim: What is a Station Model? • Do Now: R&H pp. 152-154. • 1. What is a station model? • 2. How do you indicate wind direction and wind speed on a station model? • 3. As the difference between the temperature and the dew point increases at the surface, what happens to the altitude of the cloud base? • HW- Get weather readings

16. 12-20-10What are the different types of precipitation? • Do Now: • Read pp. 141-142 • 1. What is the difference between the various types of precipitation? • Hw. Finish lab

17. 1-3-11What is an air mass and a front? • Do Now: • 1. Make a station model of today’s weather. • 2. What types of conditions favor lightning formation? • HW- R&H pp.144-146, A&E #61-69

18. Air Mass- a large parcel of air with similar conditions of temperature and humidity throughout. • An air mass takes on the qualities of the location where it comes from called a source region. • m-maritime- comes from the water and is humid. • c-continental- comes from the land and is dry. • T-tropical- comes from the equator and is warm. • P-polar- comes from the higher latitudes and is cold. • A-arctic- comes from the poles and is very cold. • Pick a lower case and an upper case letter to describe an air mass based on it’s source region.

19. Air Mass Source Regions

20. Front- the leading(front) edge of an air mass • Warm front – the leading edge of a warm air mass. Because warm air is low density it will slowly drift over air in front of it causing stratus cloud development

21. Warm Front characteristics • Warm fronts bring a long period of light precipitation in front of the front followed by whatever characteristics the new air mass contains. They are slow moving.

22. Cold Front- the leading edge of a cold air mass. • Because the cold air is high density it moves quickly and pushes air in front of it up causing cumulus cloud development and can form a short period of heavy precipitation on or behind the cold front followed by whatever conditions the new air mass brings.

23. 1-4-11What is an occluded front? • Do Now: • 1. What kind precipitation does a warm front bring and where would I find it in relationship to the frontal surface? • 2. What is a front and which air mass will always rise causing possible cloud development and precipitation? • 3. How do winds travel in a low pressure cyclone?

24. Occluded Front- when a cold front catches up to a warm front in a cyclone and the two combine. Produces very heavy precipitation.

25. 1-6-11What is a mid latitude cyclone? Do Now- Describe how an occluded front forms and what kind of weather it brings. HW- R&Hpp.147-150, A&E #70-77

26. Mid-Latitude Cyclones • Form as a result of converging cP air from the north and mT air from the south. • They start as converging air creating low pressure cyclones. • Cold fronts catch up to warm fronts and form occuluded fronts which produce thunder cells. • The cyclones spin counter clockwise and inward and generally move to the northeast in the US. • These storms can result in thunderstorms, hail storms, tornadoes, hurricanes or blizzards.

27. Hurricanes,Tornadoes, Blizzards • Hurricanes- low pressure cyclones forming in tropical waters and growing to a massive size. Suck up tremendous amounts of water and create violent wind (74mph or more), heavy rain bands, and storm surge waves. Can last for a week or more and cause the most damage when making landfall. Go to high ground and under shelter. • Tornadoes- low pressure cyclones forming from a mid-latitude cyclone on land. Winds up to 300 mph are concentrated into a narrow funnel cloud which acts like a vacume cleaner. Last generally from a minute to an hour. Go underground if possible. • Blizzards- a storm with winds of 35 mph or better with tremendous amounts of snowfall.