1. AOS 100: Weather and Climate Instructor: Nick Bassill Class TA: Courtney Obergfell

2. Some Basic Info Class website: http://www.aos.wisc.edu/~aos100nb/http://www.aos.wisc.edu/~aos100nb/ Nick’s information: - Email address: npbassill@wisc.edunpbassill@wisc.edu - Office: 1451 Atmospheric and Oceanic Sciences - Office hours: 4-5 W, 2:30-3:30 R* Courtney’s information: - Email address: obergfell@wisc.eduobergfell@wisc.edu - Office: 1311 Atmospheric & Oceanic Sciences - Office hours: 11-12:15 M, 2:40-3:40 T* * And by appointment

3. Class Overview Every class will have a rather intensive weather discussion that will focus on anything interesting going on weather-wise, as well as the forecast for Madison Hopefully this class itself will focus as much as possible on real weather! (Think thunderstorms, hurricanes, snowstorms, along with climate and climate change, etc.) However, to get to this point, we must first cover a little background (Think how the atmosphere works, the diurnal cycle, how we observe weather, etc.)

4. Now Let’s Get Our Learn On …

5. What does “Remote Sensing” Mean? “Remote sensing is the small or large- scale acquisition of information of an object or phenomenon, by the use of either recording or real-time sensing device(s) that are not in physical or intimate contact with the object” -From: http://en.wikipedia.org/wiki/Remote_sensing

6. Primary Types For meteorological considerations, there are two primary types of remotely sensed observations: (1)RADAR (2)Satellite

7. RADAR RADAR is an acronym for “RAdio Detection And Ranging” RADAR uses radiowaves or microwaves to detect objects RADAR dishes send out a pulse of electromagnetic radiation, which can be reflected back by objects The length of time it takes for the pulse to return, as well as the strength of the return pulse indicate how near/far and how big the object(s) are - From: http://en.wikipedia.org/wiki/Radar

8. RADAR Continued RADAR was largely developed before and during World War II as a method of detecting enemy ships and airplanes However, it was noticed that this was less effective when it was raining or snowing This eventually led to the widespread use of RADAR for detecting weather phenomena

9. More RADAR The RADAR beam is directed at a slight angle above the horizon (~0.5º) This ensures that the beam is not immediately blocked by nearby trees, buildings, etc. The intensity of return is measured in “decibels” (DBZ), which uses a logarithmic scale

10. http://www.bergenskywarn.org/Pages/BergenSkywarnUptonOpenHouse2001.htm From:http://www.centennialofflight.gov/ess ay/Dictionary/radar/DI90G1.jpg Pictures

11. http://www.tropicalstorms.us/current/radar.gif

12. Thunderstorms over Michigan

13. Doppler RADAR Doppler RADAR makes use of the “Doppler Effect” to determine whether objects are traveling towards or away from the radar site Doppler RADAR measures the change in wavelength of the incoming signal (compared with the signal that was sent out) http://www.grc.nasa.gov/WWW/K-12/airplane/Images/doppler.gif

14. Velocity (from the Doppler RADAR) This feature is extremely useful for detecting tornadoes – many tornadoes are first “detected” using this method

15. Satellites Unlike RADAR, satellites observe the weather exclusively from space The widespread use of satellites for meteorological purposes are a by-product of the “space race” which began in the 1950s There are two primary types of satellite (orbits): Polar Operational Environmental Satellite (POES) and Geostationary Operational Environmental Satellite (GOES)

16. POES vs. GOES POES(s) orbit around the poles fairly close to the Earth (~850 km above) GOES(s) orbit much further above the surface (~36,000 km), and always remain above the same location on the equator

17. GOES Since they remain over the same location, they constantly transmit images of the same location at a rate of about 15 minutes Because they are high above the Earth’s surface, they capture a large portion of the Earth with each image However, the spatial resolution is lower as a result

18. POES POES(s) rotate around the Earth, so the point on the Earth’s surface that they are above constantly changes POES(s) are very close to the Earth, so the images have very high spatial resolution However, the temporal resolution is very poor (about two images a day for any one location)

19. Examples GOES POES

20. Types of Imagery Visible: - This imagery can only measure visible light (~0.6 µm wavelength) - Therefore, it can only be used during the daytime Infrared (IR): - This imagery uses infrared radiation (~10-12 µm wavelength), and therefore can operate at any time of day - Here, colors (or shades of gray) depend on the color of the emitting object Water Vapor: - This imagery uses a wavelength (~6.6 µm) that is strongly absorbed by water vapor, and can be used any time of day - Bright white areas indicate lots of water vapor (often clouds), while dark areas indicate a much drier atmosphere