Transcript Chapt 9 - Judith Curry's Home Page

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
 
High-frequency
measurements

Rarely available
FQSH
0  c pd w ' ' 0

FQLH
0  Llv w ' qv ' 0
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
 c pCDH ua  u0 a 0 
LH
Q0
 LlvCDE ua  u0 qva  qv 0 
F
F
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 Ri B 
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 Pr 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
 0.0063TIa  T0 
Long term
contribution to
surface energy
budget small
Commonly
Neglected
FQoPR  s c ps Ps Tla  To   s Lil Ps
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).