Atmospheric Physics I

1. Atmospheric Physics I PHYS 621, Fall 2011 Dr. Zhibo Zhang Contact info: Phone: 410-455-6315 (office) Email: Zhibo.Zhang@umbc.edu Office hour: Friday, 3:30~4:30 or by appointment Course Website: UMBC Blackboard system & http://userpages.umbc.edu/~zzbatmos/research/PHYS621_fall2011.html

2. Textbooks Salby, Murry L. Fundamentals of Atmospheric Physics1996 Wallace J.M., and Hobbs, P.V. Atmospheric Science 2nd. Ed 2006 (don't get the green one)‏

3. Grade and Homework • Grade: Homework (30%), Midterm (30%), Final (30%), Participation/Discussion(10%) • Homework: Submit homework by 4:30pm on the due day (during class, to my office, or through Email (only pdf format accepted)) • Put your name, student ID number, and e-mail address at the top of the first page. • Please STAPLE your homework pages together so that pages do not become lost. • Homework solutions can be prepared either with pen/pencil or a word processor, as long as it looks neat and not sloppy. • Please solve the homework problems in the order assigned • Please write on the front of each solution page only and not on the back. • The homework you turn in must be your own work, in accordance with the student conduct code mentioned in the syllabus.

4. Quiz #0 • What ........ is your name? • What do you expect to learn from this class? • Have you taken a Thermo course before? Dynamics (e.g., fluids, mechanics, etc.)? • What level of mathematics have you ... • learned, and • remember? • In order to succeed in this class, which (if any) of the following are true (more than one answer is possible)‏ • Bribe the professor(s) with frosty beverages. • Be able to derive and memorize every single equation. • Show your work on your homework and tests. • Come to class having read the relevant chapters and notes, ready to answer questions.

5. How to succeed in this course(and in graduate school)‏ • Come to class prepared, take notes, work together on homework (not tests), and ask lots of questions! • Be prepared to answer questions in class. • Teach yourself how to learn independently, manage your time, and how to study effectively. • Always show your work – this means using analytic expressions (equations), figures, dimensional analysis. (see handout)‏ • Note: Plugging in numbers generally appears at the very last step in solving a problem! • Think about your qualifying exam with respect to the lessons learned in this course.

6. Lecture 1 Overview of Earth’s Atmosphere

7. Sun and Earth The Sun: Our ultimate source of energy Surface temperature: ~5800K; Distance from Earth:149.6 million km Mother Earth: Radius: 6371km; Surface temperature: ~287k (14°c);

8. Earth: Orbit and rotation Spring Summer Fall Winter

9. Latitude and Longitude Longitude: “Zonal” : East / West Latitude: “Meridional” : North / South

10. Spherical coordinate r: radius of the earth θ: Longitude Φ: Latitude Spherical Distance: radius X angle Distance on a longitude circle Distance on a latitude circle

11. Geographic Zones 66.5N 23.5 N Tropics 23.5 S Mid-latitude 66.5S 66.5N Tropics 23.5S ~ 23.5N 23.5S ~ 66.5S Mid-Latitude 23.5N ~ 66.5N 66.5N ~ 90N 66.3S ~ 90S Polar 66.5S Polar

12. Composition of atmosphere Trace gas Other constituents: Aerosols (particulates other than water),liquid and solid water, birds, insects, airplanes, kids on trampolines, etc.

13. Parts-per expressions • parts-per million (ppm), 1 × 10−6. This is equivalent to one drop of water diluted into 50 liters (roughly the fuel tank capacity of a compact car) • parts-per billion (ppb): 1 × 10−9. This is equivalent to one drop of water diluted into 250 chemical drums (50 m3), or about three seconds out of a century. • Parts-per trillion (ppt): 1 × 10-12, This is equivalent to one drop of water diluted into 20 Olympic-size swimming pools (50,000 m3), or about three seconds out of every hundred thousand years. volume mixing ratio Carbon-dioxide : 0.038% = 380x10-6=380ppm Methane: 0.0001745% = 1745x10-9=1745ppb

14. Pressure and Density Density: ρ Volume: V Gravity:g Area: A Density: mass/volume~kg/m-3 Pressure: mass x gravity / area=kg x m/s-2 / m-2= kg·m−1·s−2 • Air density: 1.25 kg m-3 (water~1000kg m-3) • Surface Pressure: 1013 hPa = 101,300 N/m-2 or 101,300 kg·m−1·s−2

15. Hydrostatic equilibrium Ftop = (P + dP)A Density: ρ Hydrostatic equilibrium: Fbot− Ftop= G -dPA = ρ g A dz Hydrostatic Equation dP/dz = -ρg z+dz z Fbot= P A G=ρ g A dz

16. Pressure and Density • The atmosphere is approximately in hydrostatic balance • The pressure at any point in the atmosphere is equal to the weight per unit area of the atmosphere above that point. • Units of pressure: Pascal [Pa] = 1 N m-2 • Air density (sea level): • ~ 1.25 kg m-3 • (The ocean: ~ 1000 kg m-3) • Air pressure (sea level): • ~ 1013 hPa • (1 hPa = 100 Pa = 1 mb)‏

17. Scale Height • Pressure (and density) generally decrease exponentially with height. • H is the “scale height”, which is the e-folding depth, p0 is the reference pressure, usually at sea-level (z=0).

18. Temperature Temperature: a measure of the average kinetic energy of the molecules in an object/gas The temperature of a classical ideal gas is related to its average kinetic energy via the equation Kinetic energy ~: on average, how fast the small balls move and their mass Temperature: A macro-physical parameter to measure the microphysical movement

19. Surface temperature

20. Vertical structure Stratosphere: A thick ozone layer (or not ~ ozone whole) in stratosphere protects us from “bad” UV Troposphere: Where we live in Contain: 75% of mass and 99% water of the whole atms. Lapse Rate: local rate of decrease of temperature (T) with altitude (z): Typical lapse rate close to surface: 6.5K/km

21. Wind Wind Direction A vector: speed and direction North wind West wind (westly) Prevailing Wind Tropical: Eastly trade wind Mid-latitude : Westly

22. “Trade” wind Spanish Portuguese

23. PrecipitationRain, Snow, Hail… • Important: • A major component of the water cycle • Responsible for depositing most of the fresh water on the planet. • Numbers: • Approximately 505,000 km3of water falls as precipitation each year • Global annual mean precipitation rate ~990mm (39 in) or 2.7mm/day

24. NOT Distributed Evenly

25. The Capacity of a system to hold a substance Residence time The Rate of flow of the substance into the system The smaller the Residence Time ~ The faster the Cycle

26. Average reservoir residence times capacity of the system Water Residence Time = flow for the system

27. Carbon Cycle

28. Atmospheric CO2

29. Global Energy Budget Incoming Solar Radiation Outgoing Longwave Radiation To keep Earth’s Energy Budget Balance Incoming Solar Radiation=Outgoing Longwave Radiation

30. Global Energy Budget 342-107=235

31. Review • Important things to remember • Surface temperature of Sun and Earth • Atmospheric composition • Atmospheric vertical structure • Sea surface pressure • Important concepts to understand • Spherical coordinate • Hydrostatic equilibrium • Lifetime and cycles • Energy budget balance concept

32. Things for you to do next: • Read: Chapter 1 in both Salby and WH, also your handout . Read Chapter 2 of WH. • Homework: Due on next Thursday (Sep.8th )

33. System of units Base Units Prefix of SI units