Chapter 9

Sea Surface Temperature

Ocean and atmosphere Stability

Surface heat fluxes

CouplingProcesses

Energy transfer

Net surface radiation flux

Sensible and latent heat

Heat transfer by Precip.

Storage and transport of energy below the ocean

Salinity

Just one example…

Do we need coupling and fluxes??

Processes in the interface permit interaction each time step

Ocean Surface Energy Budget

LHQF 0

SHQF 0

PRQF 0

advQF 0

entQF 0

netQF 0

radQF 0

advQF 0

Net surface radiation flux

Sensible heat

Latent heat

Heat transfer by precipitation

Transport of energy via fluid

motions

Transport of energy via fluid

motions Via entrainment

Storage

Ocean

Adding heat

Removing heat

00 '' wcF pdSH

Q

00 '' vlvLH

Q qwLF

Surface turbulent heat fluxes

Sensible heat flux

Latent heat flux

Covariances

High-frequency measurements

Rarely available

Estimate in terms of other parameters

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

B

a

DEDH Rif

zz

kCC 2

0

2

ln

0BRi

0BRi

0BRi

Surface turbulent heat fluxes

000 aaDHpSH

Q uuCcF

000 vvaaDElvLH

Q qquuCLF

Richardson number

Stable

unstable

Neutral

Just above the surface

Aerodynamic transfer coefficientsUnder Ordinary conditions

Bulk aerodynamic formulae

Small for statically stable conditions

Large for unstable conditions

The magnitude of the heat transfer is inversely proportional to the degree of stability

Aerodynamic transfer coefficients

0BRi

0BRi

0BRi

Stable

unstable

Neutral

oWarpllPR

Qo TTPcF

oWa TT

Snow?? Latent heat Melt Snow

silsolaspssPR

Qo PLTTPcF

00 0063.0 TTL

TTcIa

il

Iaps

Heat flux for precipitation

heat transfer occurs if the precipitation is at different temperature than the surface !!!

Temperature of the rain drop

If thermal equilibrium

Train= wet bulb T of the atmosphere

Greatest for large rainfall rates and large differences in temperature

Usually Heat flux from rain cools the ocean

Long term contribution to surface energy budget small

Commonly Neglected

The latent heat is an order of magnitude larger than sensible heat term

Variation of surface energy budget components

LHQo

SHQo

F

FB 0

Bowen Ratio

mm/yr

Artic Ocean 97 53

Atlantic Ocean 761 1133

Indian Ocean 1043 1294

Pacific Ocean 1292 1202

All Oceans 1066 1176

0EPImportant regional differences

Ocean Surface Salinity Budget

Precipitation

Evaporation

Formation of sea ice

Melting of sea ice

River runoff

Storage transport below the ocean surface

P-E

average 1959-1997

Global river runoff

Fresh-water input to the southern oceans comes from melting

net

snetQ

pB FF

cgF 00

00

Ocean Surface Buoyancy flux

Negative value meets the instability criterion

Sinking motion in the ocean

Precipitation

Evaporation Increases the buoyancy flux

Ratio of the cooling term to the salinity term of evaporation

Tropics T=30 C; s=35 psu

T=0 C; s=35 psu

8.0

0.60sc

L

p

lv

High latitudes

decreases and increases the buoyancy flux

Freshening effects of rain dominate the cooling effects of rain at all latitudes

Snow Freshening dominates the effect on the buoyancy flux

Ice/ocean

Penetration of solar radiation beneath the ice

Latent heat associated with freezing or melting ice

Heat flux terms that influence the surface

Sea Ice growsIncrease salinity

releases latent heat

Typical polar conditions

Salinity term dominates in determining ocean surface buoyancy flux

Air masslarge body of air that has similar temperature and moisture properties throughout.

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

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

Source regions

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.

Classification:

By thermal properties

Tropical (T)

Polar (P)

Artic or Antarctic (A)

By moistureContinental (C)

Maritime (m)

Also Cold (K) Warm (W)

Continental Arctic (cA):

Continental polar (cP):

Maritime polar (mP):

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

not as cold as Arctic air massesform during the summer, but usually influence only the northern USA

Cool and moist

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 moistureoriginate over the warm waters of the southern Atlantic Ocean and the Gulf of Mexicocan form year round

Maritime tropical (mT):

Continental Tropical (cT):

Hot and very dry

usually form over the Desert Southwest and northern Mexico during summer

Water mass

Water masses are identified by their temperature, salinity, and other properties such as nutrients or oxygen content.

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

Different inputs of freshwater

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).

all water masses gain their particular characteristics because of interaction with the surface during their development.

process is very slow

their names generally incorporate information about the depth levels they occur at

surface water 0-200 meters

intermediate water 200-1500 meters deep water 1500-4000 meters

bottom water deeper than deep waterNorth 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).

Water mass