| NATS 101 Lecture 21 Atmo-Ocean Interactions El Ni–o-Southern Oscillation |
| Summary |
| Global Circulation | |
| Differential Heating Between Tropics and Poles | |
| Three Cells: Hadley-Ferrel-Polar | |
| Mid-Latitude Westerlies | |
| Patterns shift slightly with seasons | |
| Precipitation | |
| Major Deserts occur under Sub-Tropical High | |
| Mid-latitude storms occur along Polar Front |
| Triple Cell (~Real World) |
| Equator-to-Pole temperature difference and rotation of Earth produce 3 circulation cells | |
| Hadley Cell (Thermally Direct) | |
| Ferrel Cell (Indirect: Forced by Hadley & Polar) | |
| Polar Cell (Thermally Direct) |
| Global Circulation - Precipitation |
| Prevailing Winds |
| Ocean Currents |
| Drag from wind exerts a force on the ocean surface in the same direction as the wind. | |
| Currents of upper ocean are due to wind. | |
| Tend to flow in the direction of prevailing wind. | |
| Poleward currents are warm; equatorward currents are cold. | |
| Thus, oceans transport heat from the tropics to the poles, about the same amount of heat as the wind. |
| Ocean Currents of World |
| Summer SST Along West Coast |
| Sea surface temperatures (SST) along West Coast are quite cold during summer, especially off Northern California. | |
| Due to upwelling of cold, nutrient rich water by prevailing N winds. |
| Ekman Spiral |
| Upwelling from Alongshore Winds |
| Slide 11 |
| 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 16 |
| Slide 17 |
| Slide 18 |
| Slide 19 |
| Slide 20 |
| Slide 21 |
| Current ENSO conditions |
| Slide 23 |
| Slide 24 |
| Slide 25 |
| Slide 26 |
| Slide 27 |
| ENSO-Atmosphere Feedback |
| 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 |
| Assignments |
| Following Lecture | |
| Topic - Air Masses | |
| Reading - Ahrens pg 201-212 | |
| Problems - 8.1, 8.11 |