Long Waves in Ocean CirculationMore Long WavesSlide 3Kelvin WavesSlide 5Slide 6Coastal Kelvin WavesSlide 8Slide 9Slide 10Slide 11Equatorial Kelvin WavesSlide 13Slide 14Slide 15Slide 16Slide 17TOGA-TAO ArrayMooringsTAO MooringsYesterday…PowerPoint PresentationSlide 23Rossby WavesSlide 25Slide 26Slide 27Rossby WavesSlide 29Slide 30Slide 31Interactions Among Rossby & Kelvin WavesEquatorial Kelvin & Rossby WavesEl Niño ConditionsSlide 35Slide 36Long Waves in Ocean Circulation•Wave response of ocean to transient conditions such as changes in wind forcing•Two dominant wave types– Rossby waves - westward propagating– Kelvin waves - travel along boundaries•Space scales of 100’s km & time scales of a few months to a few yearsMore Long Waves •How ocean “communicates” within a basin•Kelvin wave pulse is the precursor of an ENSO event•Hard to detect from direct field obs due to the scales involved•Satellite altimetry though is usefulMore Long Waves •Can be barotropic or baroclinic in natureBarotropic waves propagate fast (many m/s)Baroclinic waves are slower (several cm/s)Kelvin Waves •Needs boundary or “wave guide” to pile against– Coastal boundary – The equator or “double” Kelvin wave•Can be wave of depression or elevation•How ENSO pulse is transmitted in oceanKelvin Waves Wave of depressionGreatest onshorePropagates CCW in a NH basin (CW in SH)Kelvin Waves •Simple geostrophic balance (HPF = CF)•Propagates into the page•Wave of depression would go in same directionCoastal Kelvin WavesCoastal Kelvin WavesCoastal Kelvin WavesCoastal Kelvin WavesCoastal Kelvin WavesEquatorial Kelvin Waves •Simple geostrophic balance (HPF = CF)•Two Kelvin waves “rest” against each other on equator - double Kelvin waves•Propagates to the eastEquatorial Kelvin WavesEquatorial Kelvin WavesEquatorial Kelvin Waves •Satellite altimetry from TOPEX/Poseidon•Scenes are 10 days apartKelvin Waves •NH CCW propagation•SH CW propagation•Way of building time cycles into ocean (climate oscillators)Equatorial Kelvin WavesTOGA-TAO Array •Equatorial array of buoys•U.S., Japan & French partnership•http://www.pmel.noaa.gov/tao/Moorings •Measure met & ocean properties•Thermocline focus •Real-time data transmission•Used in weather & climate forecastsTAO MooringsYesterday…Propagates 13,000 km in 4 months - 1.3 m/sKelvin Waves •Needs boundary or “wave guide” to pile against– Coastal boundary – Equatorial boundary or “double” Kelvin wave•Can be wave of depression or elevation•Baroclinic waves travel at 1-2 m/sRossby Waves •Propagate zonally from east to west•Results from conservation of potential vorticity, PV = ( + f)/D•Propagation speeds are slow (< 5 cm/s) poleward of 30o•Wave speeds increase dramatically towards equatorRossby WavesRossby WavesRossbyWavesRossby WavesmovieRossby WavesRossby WavesRossby Waves •Propagate zonally from east to west•Results from PV conservation •Propagation speeds are slow (< 5 cm/s) poleward of 30o•Wave speeds increase dramatically towards equatorInteractions Among Rossby & Kelvin Waves •Kelvin waves can excite Rossby waves•Occurs in equatorial & coastal wave guides•Important for progression of El Nino eventsEquatorial Kelvin & Rossby WavesEl Niño ConditionsInteractions Among Rossby & Kelvin Waves •Kelvin waves can excite Rossby waves•Occurs in equatorial & coastal wave guides•Important for progression of El Nino
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