| NATS 101 Intro to Weather and Climate Lecture 7 Seasonality |
| Supplemental References for TodayÕs Lecture |
| Aguado, E. and J. E. Burt, 2001: Understanding Weather & Climate, 2nd Ed. 505 pp. Prentice Hall. (ISBN 0-13-027394-5) | |
| Danielson, E. W., J. Levin and E. Abrams, 1998: Meteorology. 462 pp. McGraw-Hill. (ISBN 0-697-21711-6) | |
| Gedzelman, S. D., 1980: The Science and Wonders of the Atmosphere. 535 pp. John-Wiley & Sons. (ISBN 0-471-02972-6) | |
| Lutgens, F. K. and E. J. Tarbuck, 2001: The Atmosphere, An Intro-duction to the Atmosphere, 8th Ed. 484 pp. Prentice Hall. (ISBN 0-13-087957-6) | |
| Wallace, J. M. and P. V. Hobbs, 1977: Atmospheric Science, An Introductory Survey. 467 pp. Academic Press. (ISBN 0-12-732950-1) |
| Reasons for Seasons |
| Tilt of EarthÕs Axis - Obliquity | |
| Angle between the Equatorial Plane and the Orbital Plane | |
| Eccentricity of EarthÕs Orbit | |
| Elongation of Orbital Axis |
| Eccentricity of Orbit |
| Slide 5 |
| Solar Zenith Angle |
| Depends on latitude, time of day & season | |
| Has two effects on an incoming solar beam | |
| Surface area covered or Spreading of beam | |
| Path length through atmosphere or Attenuation of beam |
| Beam Spreading |
| Low Zenith - Large Area, Much Spreading | |
| High Zenith - Small Area, Little Spreading |
| Beam Spreading |
| Atmospheric Path Length |
| Length of Day |
| Day Hours at Solstices - US Sites |
| Summer-Winter | |
| Tucson (32o 13Õ N) 14:15 - 10:03 | |
| Seattle (47o 38Õ N) 16:00 - 8:25 | |
| Anchorage (61o 13Õ N) 19:22 - 5:28 | |
| Fairbanks (64o 49Õ N) 21:47 - 3:42 | |
| Hilo (19o 43Õ N) 13:19 - 10:46 |
| Path of Sun |
| Hours of daylight increase from winter to summer pole | |
| Equator always has 12 hours of daylight | |
| Summer pole has 24 hours of daylight | |
| Winter pole has 24 hours of darkness | |
| Note different Zeniths |
| Noon Zenith at Solstices |
| Summer-Winter | |
| Tucson AZ (32o 13Õ N) 08o 43Õ - 55o 43Õ | |
| Seattle WA (47o 38Õ N) 24o 08Õ - 71o 08Õ | |
| Anchorage AK (61o 13Õ N) 37o 43Õ - 84o 43Õ | |
| Fairbanks AK (64o 49Õ N) 41o 19Õ - 88o 19Õ | |
| Hilo HI (19o 43Õ N) 3o 47Õ (north) - 43o 13Õ |
| Incoming Solar Radiation
(Insolation) at the Top of the Atmosphere |
| Is Longest Day the Hottest Day? |
| Annual Energy Balance |
| Heat transfer done by winds and ocean currents | |
| Differential heating drives winds and currents | |
| We will examine later in course |
| Summary |
| Tilt (23.5o) is primary reason for seasons | |
| Tilt changes two important factors Angle at which solar rays strike the earth Number of hours of daylight each day | |
| Warmest and Coldest Days of Year Occur after solstices, typically around a month | |
| Requirement for Heat Transport Done by Atmosphere-Ocean System |
| Assignment for Lecture |
| Ahrens | |
| Pages 55-64 | |
| Problems 3.1, 3.2, 3.5, 3.6, 3.14 |