1. AOSC 200 Lesson 5

2. Observing the Atmosphere There are several instruments that are used to measure the basic atmospheric variables/ Temperature – Thermometer –Mercury –Resistance Pressure – Barometer Humidity – psychrometer, dew point hygrometer Wind Speed - Anemometer Wind Direction – Wind vane Precipitation – Rain Gauge

3. Max-min Thermometer

4. Temperature Measurement Max-Min thermometer Resistance thermometer Remote measurement by observing thermal IR emissions. Clinical thermometer

5. Fig. 5-3, p. 130

6. Humidity Measurements Dew-point hygrometer. Uses a laser beam and a mirror. The mirror is cooled down, and when dew is formed on the mirror, the laser beam is scattered. Wet-bulb psychrometer. Two thermometers, one wrapped with a wet cloth. Air is passed over both, the wet bulb will show a lower temperature. Relative humidity obtained from pre-calculated tables. Remote measurements using Microwave wavelengths

7. Mercury Barometer

8. Fig. 5-4, p. 131

9. Pressure Measurement Mercury barometer – long tube sealed at one end and filled with mercury, with open end immersed in a bath of mercury. Closed end has vacuum above mercury column. Height of column measures the pressure. Aneroid barometer – ‘without liquid’. Spiral thin wall cell which twists as the pressure changes. Not as accurate as the mercury barometer Electronic – transistors whose resistance is sensitive to pressure.

10. Fig. 5.4

11. Wing Gauge

12. Wind Measurement Anemometers measure wind speed Wind vanes measure wind direction Combination measures wind velocity Cup anemometers Propellers From space one can observe the speed with which clouds move

13. Rain Gauge

14. Tipping Rain Gauge

15. Fig. 5-12, p. 139

16. Radar Observations RAdio Detection And Ranging Pulse of radio waves is sent out from transmitter. Time it takes for the pulse to return gives the distance to the cloud/precipitation. The amount of the pulse that is scattered can be used to tell how much rain is falling. Doppler effect Doppler RADAR can detect wind speed Wind profiler

17. Fig. 5.19

18. Fig. 5.21a

19. Fig. 5.21b

20. Plot of boundary layer winds from the Fort Meade, MD wind profiler during a high ozone episode LLJ

21. Fig. 5-13, p. 140 Geosynchronous Orbit

22. Sun-synchronous (polar) orbit

23. Satellite Observations Two principle orbits are used Sun-synchronous, aka polar orbiter, LEO Orbits in the sun-earth plane, crosses over the poles. NOAA LEO cross the equator at 2.00 pm and 2.00 am each day. Each orbit takes about 90 minutes Geosynchronous – orbits around the earth always above the equator. Orbital period is 24 hours, i.e. it stays above the same point on the ground.

24. Fig. 5.14 Visible image from the GOES Satellite Aug 7, 2000

25. Fig. 5.15 IR image from the GOES satellite, Aug 2, 2000

26. Fig. 5.17 Water vapor image, August 7, 2000

27. Fig. 5.22