| NATS 101-05 Lecture 16 Air Masses |
| Supplemental References for TodayŐs Lecture |
| Lutgens, F. K. and E. J. Tarbuck, 2001: The Atmosphere, An Introduction to the Atmosphere, 8th Ed. 484 pp. Prentice Hall. (ISBN 0-13-087957-6) | |
| Ocean Currents of World |
| Upwelling from Alongshore Winds |
| Slide 5 |
| El Nino-Southern Oscillation (ENSO) |
| An important atmospheric-ocean feedback | |
| Normal conditions in tropical Pacific: | |
| -Warm SST, low SLP, and T-storms in W Pacific | |
| -Strong subtropical highs in E Pacific | |
| -Easterly winds and cool upwelling water along equator in East Pacific | |
| -Prevailing southerly winds off of Peru produce cold upwelling and excellent fishing |
| El Ni–o-Southern Oscillation (ENSO) |
| Every few years (4-5 years): | |
| -Equatorial Central Pacific warms | |
| -Low SLP, T-storms shift to Central and East Pacific (the Southern Oscillation) | |
| -Trades and southerly winds off Peru weaken | |
| -Upwelling ceases off Peru, warming leads to massive kill off of fish. Typically occurs around Christmas (an El Ni–o event) | |
| FAlters global patterns of wind, temp and rain |
| Walker Circulation |
| Southern Oscillation Index (SOI) |
| Slide 10 |
| Slide 11 |
| Slide 12 |
| Slide 13 |
| Slide 14 |
| Slide 15 |
| Slide 16 |
| Slide 17 |
| Slide 18 |
| Slide 19 |
| Slide 20 |
| ENSO-Atmosphere Coupling |
| Ocean and ENSO Summary |
| Major Ocean Currents | |
| Driven by prevailing wind | |
| Upwelling Regions | |
| Occurs along west coasts of continents | |
| Cold water rises from below to surface | |
| Nutrient rich, excellent fishing regions | |
| Summary |
| El Nino-Southern Oscillation | |
| Occurs every few years | |
| Central equatorial Pacific warms | |
| Low SLP, T-storms move with warm water | |
| Upwelling weakens along Peru coast | |
| Can be predicted up to one-year in advance | |
| Modulates global patterns of wind, temp, rain |
| What is an Air Mass? |
| Air Mass | |
| Large area (>1600 km by 1600 km) of air that contains relatively uniform, horizontal distributions of temperature and moisture. |
| How Air Masses Form |
| If surface air resides in a region for a few days, it acquires the thermal and moisture characteristics of the underlying surface. | |
| Source regions for Air Masses are: | |
| Big in area [ >>(1600 km)2 ] | |
| Dominated by persistent high pressure and light winds |
| Air Mass Source Regions |
| Contrasting source regions are | |
| Continents versus Oceans | |
| Tropics versus Poles | |
| An Air Mass is designated in terms of its Source Region |
| Air Mass Characteristics |
| Air Mass Source Regions for NA |
| Creation of cP Air Mass |
| Creation of cP Air Mass |
| Creation of mP Air Mass |
| Lake Effect Snows |
| Creation of mT and cT Air Masses |
| Contrasting Air Masses |
| Paths of cP Air Masses |
| cP Air Mass |
| Modification of cP Air Mass |
| mP Air Masses |
| cT Air Mass |
| Winter mT Pacific Air Masses |
| Weather Map with Air Masses |
| Summary |
| Air Masses | |
| Large (>1000 miles) regions with ŇuniformÓ temperature and moisture characteristics | |
| Classified by Source Region | |
| Continental (c) or Maritime (m) | |
| Polar (P) or Tropical (T) | |
| Source Regions | |
| Big in area (>>1600 km by 1600 km) | |
| Dominated by light winds (long resident times) |
| Assignment for Next Lecture |
| Topic - Fronts | |
| Reading - Ahrens pg 214-231 | |
| Problems - 8.12, 8.13 |