We walk away from our dreams afraid that we might fail or worst yet afraid that we might succeed Anonymous Whatever you can do or dream you can begin it Boldness has genius power and magic in it Begin it now Goethe Global Circulation Patterns Atmosphere Atmospheric circulation results from N 1 Earth s rotation and OCNG 251 Oceanography Tuesday Nov 4th 2008 Ocean Circulation Short term Climate variability El Ni o Southern Oscillation North Altlantic Oscillation Equatorial Pacific Climate Superimposed on the North South Hadley circulation there are three main centers of convection in the inter tropical zone These centers induce a significant East West circulation in the troposphere that is most prevalent over the equatorial Pacific Walker Circulation The centers of South America and Africa are stable to movement east and west 2 differential heating at surface and in atmosphere Because it is over the ocean the convection center over the oceanic region of Southeast Asian is not stable to movement in the east west direction this produces prevailing winds and latitudinal belts of high low pressure Hadley Cells north south S Equatorial Pacific Climate In the tropical Pacific the surface winds trade winds flow westward converging towards the equator The SST climatology displays a relatively cold eastern half and a warm west zonal asymmetry The sea level atmospheric pressure is lower over the warm water than over the cold water providing additional forcing of the easterly winds on the equator Why is the eastern Pacific cold Constant easterlies cause the general westward movement of warm surface water towards the western Pacific The accumulation of water pushes down the thermocline in the west and shallows it in the east Esterlies cause Eckman divergence in the west leading to upwelling along the Peruvian coast Upwelling waters from intermediate depths decrease the SST of the eastern equatorial Pacific Convergence in the west results in intense convection over Southeast Asia and Australia which results in low pressure and abundant rainfall The mean state The contrast in SST leads to a contrast in sea level atmospheric pressure higher pressure in the east and low pressure in the west The pressure gradient maintains the surface easterlies The convergence of moist air leads to massive convection and upward motion sinking air in the east Walker Circulation This situation is unstable El Ni o When a perturbation occurs and the trade winds weaken the piled waters in the west collapse collapse and the thermocline equilibrates becomes level Waters from the west move toward the east and the cold tongue tongue is weakened The highest temperature are near the dateline central Pacific The convection migrates with the warm waters The low pressure is in the center of the basin further weakening the trade winds La Ni a When the trade winds are stronger than usual The water in the eastern half of the Pacific is colder than normal and the warmest waters are pushed further westward Australia and Southeast Asia The pressure increases further in the east Convection is pushed westward Southern Oscillation A sea level pressure seesaw seesaw between Darwin and Tahiti accompanies the El Ni o SST variation The pressure difference between the two locations produces the Southern Oscillation Index SOI Strong negative values indicate El Ni o ENSO Strong positive values indicate La Ni a non ENSO The variation in pressure in these two places is almost perfectly correlated back to 1880 Darwin Tahiti El Ni o Southern Oscillation ENSO Time series of anomalies in sea level pressure at Darwin dashed and Tahiti solid from 1970 to 1991 some smoothing was applied Chicken or the Egg Western Pacific sea surface temperature Western Pacific atmospheric convection Climate impact of El Ni o The figure shows the global impacts of El Ni o warm episodes episodes Regions with significant rise in temperature Easterly surface ocean currents Easterly surface winds Regions with significant cooling Regions experiencing rain deficit drought Regions experiencing excess rain floods Regions experiencing dryness Regions becoming wet and cold Climate impact of La Ni a The figure shows the global impacts of La Ni a cold episodes episodes Regional Climate impact of El Ni o In Texas for example wet years correspond to El Ni o years in the equatorial Pacific During El Ni o convection normally found in the western equatorial Pacific moved east into the central equatorial Pacific The subtropical jet also moves east carrying tropical moisture across Mexico to Texas and the Mississippi Valley Cold fronts in winter interact with the upper level moisture to produce abundant winter rains from Texas eastward Regions with significant rise in temperature Regions with significant cooling Regions experiencing rain deficit drought Regions experiencing excess rain floods Regions experiencing dryness Regions becoming wet and cold Correlation of yearly averaged rainfall averaged over all Texas each year plotted as a function of the Southern Oscillation Index averaged for the year From Stewart 1994 Reservoirs empty promises Take I NAO and Energy in Norway Norway experiences cold winters during a negative NAO phase Heating Oil consumption in Norway varies by 30 in good negative correlation with NAO Correlation with precipitation results in variability in hydropower generation NAO and Energy in Norway In Norway export and import of energy is relatively new An open trade market has been established Nord Pool How will the price change with climate change