1. GEOGRAPHY 120: EARTH SYSTEM II

2. Atmospheric Sciences at a Glance

3. The mission of the atmospheric sciences is to understand and predict weather and climate

4. Life cycle of the Sun and the Earth The earth will be inhabitable for another 0.5 billion years, if we protect it well enough. After another 1 billion years, all oceans and rivers will have completely disappeared. The mean global temperature will reach 160 F.

5. Some basic concepts Atmosphere: A mixture of gas molecules, microscopically small particles of solid and liquid, and falling precipitation Meteorology: The study of the atmosphere and the processes that form weather Weather: The state of the atmosphere at a given time and place Climate: The statistical properties of the atmosphere. (i.e. averages and variability)

6. Weather-related Disasters: Tropical Cyclones (Hurricanes, Typhoons, Cyclones) Global distribution of the paths of major tropical cyclones during the last 150 years. On average, ~ 80 per year around the world. U.S. Fatalities: normal year 21, Katrina 1836 U.S. Property loss: normal year $5400 million, Katrina $84000 million

7. Weather-related Disasters: Tornadoes U.S. Annual mean fatalities 56, annual mean loss $777 million

8. Weather-related Disasters: Floods U.S. Annual mean fatalities 8, annual mean loss $5300 million

9. Weather-related Disasters: Extreme Heat Annual mean fatalities 282, annual mean loss $85 million Death toll of the 2003 Paris heat wave: 15,000 (official number)

10. Summary: Weather-related Disasters in US

11. Climate-related Disasters over the world Example 1: El Nino

12. Climate-related Disasters over the world Example 2: Global Warming

13. Movie time! How do the scientists understand and predict weather and climate?

14. The modern climatology (meteorology) was born in the 1940s (a very young science!), but has been growing very fast! Carl-Gustaf Rossby (1898-1957) Generally considered as the “father of modern meteorology”. Founder of the “Chicago School of Meteorology”.

15. Observing the atmosphere: Surface weather stations 1875 (~100) 1975 (>1700)

16. Observing the atmosphere: Surface weather stations Now

17. Observing the atmosphere: Upper-air sounding stations Now (>1000)

18. Observing the atmosphere: Proxy data Proxy data (e.g. ice core, tree ring, lake sediment) can provide climate records hundreds of thousand years ago.

19. Observing the atmosphere: Weather Radar First weather radar (NOAA NSSL) Current NEXRAD Doppler radar (NOAA NWS)

20. Observing the atmosphere: Shipborne radar From Mapes and Lin (2005)

21. Observing the atmosphere: Aircraft NOAA P3

22. TIROS-1 (1960) World’s first weather satellite Observing the atmosphere: Satellite

23. NASA’s Earth Observation System A-Train Satellites Observing the atmosphere: Satellite

24. Climate Modeling on World’s Fastest Supercomputers Japan’s Earth Simulator (World’s #1 in 2004, #20 now) OSC’s new IBM machine among world’s top 100

25. World’s Major Global Climate Models

26. The current status of weather and climate predictions Weather prediction: Generally good within one week, not good beyond 10 days. The skill depends on season and location. Tropical cyclone (hurricane, typhoon) prediction: good in track, but bad in intensity Climate prediction: Seasonal prediction generally good within 6 months, but not good beyond. Skill depends on season. Climate projection: All models project global warming in the 21st century, but with a 3-fold difference in magnitude.

27. Why is it so difficult to understand and predict weather and climate?

28. Problem I: Different parts of the world are strongly connected to each other (The “Teleconnection Problem”) (Lin et al. 2006, Journal of Climate)

29. Problem II: Different components of the earth system (atmosphere, land, ocean, ice, clouds, etc) are strongly interacting with each other (The “Feedback Problem”) (Lin 2007, Journal of Climate)

30. Problem III: The earth system composes of both very big objects (such as the whole Pacific Ocean) and very small objects (such as the cloud droplets), making it very difficult to draw them on the same page (The “Subgrid-Scale Problem”) Examples: Thunderstorms, clouds, turbulence, trees, grass

31. Summary Atmosphere: A mixture of gas molecules, microscopically small particles of solid and liquid, and falling precipitation Meteorology: The study of the atmosphere and the processes that form weather Weather: The state of the atmosphere at a given time and place Climate: The statistical properties of the atmosphere. (i.e. averages and variability) Weather- and climate-related disasters: tropical cyclones, tornados, floods, droughts, winter storms, extreme heat, extreme cold, lightning, El Nino, global warming

32. Summary (cont.) The modern climatology (meteorology) was born in the 1940s (a very young science!), but has been growing very fast! Now we have a global observational network with many satellites, ships, radars and surface stations, as well as very comprehensive prediction models running on the world’s largest computers. The current status of weather and climate predictions: (1) weather prediction good to 10 days, (2) tropical cyclone prediction good in track but not in intensity, (3) climate prediction good to two seasons, (4) climate change projections have a 3-fold difference in magnitude. The main reasons of the difficulties: (1) Teleconnection problem, (2) Feedback problem, and (3) Subgrid-scale problem.