1. Atmospheric Forces: Weather and Climatology Mr. Ross Brown Brooklyn School for Law and Technology

2. How do we understand the weather? 4 January 2015 Do now: Take out your Reference Tables. – What is the dewpoint when the dry-bulb temperature is 24°C and the wet-bulb temperature is 15°C? a)8°C b)-18°C c)36°C d)4°C

3. Air Mass Large, uniform temperature and moisture content Types: – Polar (P) cold – Tropical (T) warm – Maritime (m) oceans – Continental (c) land

4. Air Masses Combinations – Maritime Polar (mP) – Maritime Tropical (mT) – Continental Polar (cP) – Continental Tropical (cT)

5. North American Air Masses

6. Air Masses An airmass originating over the North Pacific Ocean would most likely be a)continental polar b)continental tropical c)maritime polar d)maritime tropical On a weather map, an airmass that is very warm and dry would be labeled a)mP b)mT c)cP d)cT

7. Fronts Air masses of different densities meet along a Front. Warm front: warm air overtakes cool air. Warm air rises over cool.

8. Fronts Cold front: cold air mass overtakes a warm air mass, lifting the warm air. May cause storms. A big storm ahead of the front is a squall.

9. Fronts Stationary front: two air masses meet but neither is displaced

10. Fronts Occluded front: fast cold front completely lifts warm front and keeps it high in the atmosphere.

11. How do Hurricanes form? Windspeed >120 km/ hour Spiral toward intense low-pressure center Warm, moist air over ocean rises Moisture condenses, releasing heat energy

12. Wind patterns

13. The arrows on the diagram below represent surface wind directions on a weather map. The points represent the locations of four weather stations in the Northern Hemisphere. Which weather station probably has the lowest air pressure? A B C D

14. Forecasting the weather

15. Forecasting weather This question may require the use of the Earth Science Reference Tables. The station model below shows the weather conditions at Massena, New York, at 9 a.m. on a particular day in June. What was the barometric pressure at Massena 3 hours earlier on that day? Earth Science Reference Tables a)997.1 mb b)999.7 mb c)1003.3 mb d)1009.1 mb

16. The weather map Isobars: lines connecting points of equal atmospheric pressure. Lines closer together mean faster winds.

17. Heat Energy and Water Water changes state from ice  water  steam and back again Absorbs and releases heat during this process

18. Sublimation The change from ice directly to steam or steam to ice. For example, steam going out on a winter’s day.

19. Humidity Humidity: Water vapor in the atmosphere When the air holds as much water vapor as it can, it is saturated As temperature rises, ability to hold water vapor rises Relative humidity: ratio of water vapor in the air to amount that could be held (%)

20. How do we measure relative humidity? Psychrometer: instrument with 2 thermometers, one with a wet wick Dew point: temperature at which water vapor begins to condense

21. Atmospheric Pressure Gravity pulls atmospheric gases toward the Earth’s surface – 99% of mass of atmospheric gases are within 32 km of surface – A reading of 1 atmosphere = average atmospheric pressure at sea level – 1 millibar (mb) equals 0.001 of standard atmospheric pressure

22. How do we measure atmospheric pressure? Barometer – Mercurial barometer: atmospheric pressure presses on liquid mercury in a glass tube. We read how high it gets pressed.

23. How do we measure atmospheric pressure? Aneroid barometer: Sealed container with air removed. As pressure increases, sides of container bend inward.

24. Layers of the Atmosphere Troposphere: closest to Earth’s surface – Up to ~ 10 km Stratosphere: troposphere to 50 km – Ozone is contained here Mesosphere: stratosphere to 80 km Thermosphere: above

25. Layers of the Atmosphere