Chapt 9
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Chapter 9 Sea Surface Temperature Ocean and atmosphere Stability Net surface radiation flux Surface heat fluxes Sensible and latent heat Coupling Salinity Processes Energy transfer Heat transfer by Precip. Storage and transport of energy below the ocean Just one example… Do we need coupling and fluxes?? Processes in the interface permit interaction each time step Removing heat Ocean Surface Energy Budget Latent heat Net surface radiation flux Sensible heat LH Q0 SH Q0 F rad Q0 F F Heat transfer by precipitation Ocean PR Q0 F Transport of energy via fluid motions FQnet0 Storage FQadv 0 Transport of energy via fluid motions adv Q0 F ent Q0 F Via entrainment Adding heat Surface turbulent heat fluxes Sensible heat flux Latent heat flux FQSH 0 c pd w ' ' 0 FQLH 0 Llv w ' qv ' 0 High-frequency measurements Rarely available Estimate in terms of other parameters Covariances Bulk aerodynamic formulae Near-surface turbulence arises from the mean wind shear over the surface Turbulent fluxes of heat and moisture are proportional to their gradients just above the ocean surface Surface turbulent heat fluxes Bulk aerodynamic formulae SH Q0 F c pC DH ua u0 a 0 FQLH 0 LlvC DE ua u0 qva qv 0 Aerodynamic transfer coefficients Under Ordinary conditions RiB 0 Stable RiB 0 Neutral RiB 0 unstable C DH C DE Just above the surface k2 za ln z0 2 f RiB Richardson number Aerodynamic transfer coefficients RiB 0 Stable RiB 0 Neutral RiB 0 unstable Small for statically stable conditions Large for unstable conditions The magnitude of the heat transfer is inversely proportional to the degree of stability Heat flux for precipitation Temperature of the rain drop heat transfer occurs if the precipitation is at different temperature than the surface !!! If thermal equilibrium Train= wet bulb T of the atmosphere FQoPR l c pl Pr TWa To TWa To Usually Snow?? c ps TIa T0 Lil Greatest for large rainfall rates and large differences in temperature Heat flux from rain cools the ocean Latent heat Melt Snow 0.0063TIa T0 Long term contribution to surface energy budget small Commonly Neglected FQoPR s c ps Ps Tla To s Lil Ps The latent heat is an order of magnitude larger than sensible heat term Variation of surface energy budget components Bowen Ratio B0 FQoSH FQoLH Ocean Surface Salinity Budget Precipitation Evaporation Formation of sea ice Melting of sea ice River runoff Storage transport below the ocean surface P E 0 Artic Ocean 97 53 Atlantic Ocean 761 1133 Indian Ocean 1043 1294 Pacific Ocean 1292 1202 All Oceans 1066 1176 mm/yr Important regional differences P-E average 1959-1997 Global river runoff Fresh-water input to the southern oceans comes from melting Ocean Surface Buoyancy flux FB 0 net net g FQ 0 Fs 0 c p 0 Evaporation Ratio of the cooling term to the salinity term of evaporation Negative value meets the instability criterion Sinking motion in the ocean Increases the buoyancy flux Llv c p s0 Precipitation Tropics High latitudes T=30 C; s=35 psu 8.0 T=0 C; s=35 psu 0.6 decreases and increases the buoyancy flux Freshening effects of rain dominate the cooling effects of rain at all Snow latitudes Freshening dominates the effect on the buoyancy flux Ice/ocean Heat flux terms that influence the surface Penetration of solar radiation beneath the ice Latent heat associated with freezing or melting ice Increase salinity Sea Ice grows Typical polar conditions Salinity term dominates in determining ocean surface buoyancy flux releases latent heat large body of air that has similar temperature and moisture properties throughout. Air mass Source regions The best for air masses are large flat areas where air can be stagnant long enough to take on the characteristics of the surface below uniform surface composition - flat light surface winds The longer the air mass stays over its source region, the more likely it will acquire the properties of the surface below. Once an air mass moves out of its source region, it is modified as it encounters surface conditions different than those found in the source region. For example, as a polar air mass moves southward, it encounters warmer land masses Classification: Tropical (T) By thermal properties Polar (P) Continental (C) By moisture Artic or Antarctic (A) Also Cold (K) Warm (W) Maritime (m) Continental Arctic (cA): Extremely cold temperatures and very little moisture. originate north of the Arctic Circle, where days of 24 hour darkness allow the air to cool very rarely form during the summer Continental polar (cP): not as cold as Arctic air masses form during the summer, but usually influence only the northern USA Cool and moist Maritime polar (mP): Maritime tropical (mT): form over the northern Atlantic and the northern Pacific oceans can form any time of the year and are usually not as cold as continental polar air masses. Warm temperatures and moisture originate over the warm waters of the southern Atlantic Ocean and the Gulf of Mexico can form year round Hot and very dry Continental Tropical (cT): usually form over the Desert Southwest and northern Mexico during summer Water mass Two basic circulation systems in the oceans the wind-driven surface circulation the deepwater density-driven circulation Only about 10% of the ocean volume is involved in wind-driven surface currents. The other 90% circulates due to density differences in water masses Water masses are identified by their temperature, salinity, and other properties such as nutrients or oxygen content. Different inputs of freshwater all water masses gain their particular characteristics because of interaction with the surface during their development. Patterns of precipitation Evaporation temperature regimes Once water masses sink, their temperature and salinity are modified primarily by mixing with other water masses (diffusive and turbulent heat exchange). process is very slow Water mass surface water 0-200 meters their names generally incorporate information about the depth levels they occur at intermediate water 200-1500 meters deep water 1500-4000 meters bottom water deeper than deep water North Atlantic Deep Water forms in the region around Iceland. North Atlantic Intermediate Water has come near the surface and has been cooled by the contact with the air. Mediterranean Outflow Water is a deep water mass that results from high salinity, not cooling. Antarctic Bottom Water is the most distinct of all deep water masses. It is cold (-0.5°C or 31.1°F) and salty (34.65 parts per thousand).
