Lecture 16Outline of Last Lecture I. Scales and LifespanII. How is Forecast Made?III. Sources of DataIV. Surface Station NetworkV. Rawinsonde NetworkVI. Satellite ImageryVII. RadarVIII. The National Weather ServiceIX. WatchesX. WarningsXI. Watches, Warnings, and AdvisoriesXII. Weather ForecastingXIII. Review of FrontsXIV. Computer ModelsXV. Weather ModelingXVI. Numerical Weather PredictionOutline of Current Lecture XVII. Oceanic GyresXVIII. Oceanic TemperatureXIX. UpwellingXX. DefinitionsXXI. ENSO: Normal ConditionsXXII. ENSO Warm Phase: El NinoATMS 100 1st EditionXXIII. Effects of El NinoXXIV. ENSO Cool Phase: La NinaXXV. Are We Headed for El Nino?XXVI. Historical ENSO Events?Current LectureXXVII. Oceanic Gyresa. Ocean currents form an anticyclonic circulation (or gyre) in each ocean, in each hempispherei. warm currents east of continentsii. cold currents west of continentsb. 40% of heat transport in Northern Hemisphere occurs in oceansXXVIII. Oceanic Temperaturea. Warmest water typically found at ocean surfacei. absorbs solar radiationb. rapid temperature decrease with depth a few hundred meters below surfacei. called thermoclinec. deep ocean waters only a few degrees above freezingi. even in summer and near equatorii. very darkXXIX. Upwellinga. Upwellingi. vertical transport of deep ocean waters upward1. upwelling results in cooler surface water temperatures2. temperature decreases with depthii. typically occurs along west coast of continentsiii. water temperatures along US west coast only reach upper 50’s-lower 60s (F) in summer1. results in cooler summers along west coastXXX. Definitionsa. El Ninoi. wamer than average water in the Pacific ocean off South Amer-icab. La Ninai. cooler than average water in the Pacific Ocean off South Amer-icac. ENSOi. El Nino Souther Oscillationd. Southern Oscillationi. atmospheric oscillation over South Pacific Ocean. ii. encompasses both El Nino and La Ninae. Trade Windsi. easterly winds that blow along equatorXXXI. ENSO: Normal Conditionsa. Surface Low pressure near Indonesia (clouds/rain); high pressure nearSouth Americai. Results in easterly (NE in NH, SE in SH) winds across equato-rial Pacific1. Trade Windsb. As winds push water from east to west, water is warmed by sunlighti. warmer water to west, cooler water to eastii. higher sea level, deeper layer of warm water to west c. Warm, moist air rises over western south pacific oceani. clouds, heavy precipitation d. Air sinks near the west coast of South Americai. clear skies, little precipiationii. driest place on earth: Atcama Desert, Chile. Portions average 1 mm of rain a yearXXXII. ENSO Warm Phase: El Ninoa. Pressure Gradient weakens across equatorial Pacifici. reasons why unknownii. easterly winds weakenb. Warm water flows eastward across Pacificc. Walker circulation reverses: Clouds/Rain in east; dry in westd. Typically reaches maximum around Christmasi. Called “El Nino” means “boy child” refers to Christ Childe. May last for many months. affects large area, occurs every 2-7 yearsi. event ends as surface pressure field returns to normalii. vary in length and durationXXXIII. Effects of El Ninoa. Water temperatures may be 6 degrees celcius (11 F) warmer than nor-mal in Eastern Pacificb. Warm water in nutrient poor (no upwelling)i. dead fish, dead birdsc. dry weather in western pacific, wet weather in eastern Pacific d. Tropical cyclones (hurricanes/typhoons)i. increase in eastern/central Pacificii. decrease in western Pacific and all of AtlanticXXXIV. ENSO Cool Phase: La Ninaa. Pressure gradient strengths across equatorial Pacifici. reasons why unknownii. easterly trade winds strengthen; cool water flows acorss Pacificiii. Walker circulation strengthens: more clouds/rain in west; drier ineastb. Increase upwelling near South