Lecture 2: Structure and Composition of the Atmosphere and ... · Lecture 2: Structure and...
Transcript of Lecture 2: Structure and Composition of the Atmosphere and ... · Lecture 2: Structure and...
The atmosphereEquation of state and hydrostatic balance
The ocean
Lecture 2:Structure and Composition of the Atmosphere and Ocean
Jonathon S. Wright
28 February 2017
The atmosphereEquation of state and hydrostatic balance
The ocean
The atmosphereTemperature structureMajor constituentsGreenhouse gases
Equation of state and hydrostatic balanceThe atmospheric equation of stateHydrostatic balance
The oceanCompositionEquation of stateVertical structure
The atmosphereEquation of state and hydrostatic balance
The ocean
Temperature structureMajor constituentsGreenhouse gases
180 200 220 240 260 280 300Temperature [K]
0
20
40
60
80
100
Alti
tude
abo
ve s
ea le
vel [
km]
Troposphere
Stratosphere
Mesosphere
Thermosphere
Tropopause
Stratopause
Mesopause
data from 1976 US Standard Atmosphere
The atmosphereEquation of state and hydrostatic balance
The ocean
Temperature structureMajor constituentsGreenhouse gases
The Lapse Rate
Γ = −dTdz
The atmosphereEquation of state and hydrostatic balance
The ocean
Temperature structureMajor constituentsGreenhouse gases
Gas Percent by volume
Nitrogen (N2) 78.08%Oxygen (O2) 20.95%Argon (Ar) 0.93%Water Vapor (H2O) 0.00001–4.0%Carbon Dioxide (CO2) 0.039%Neon (Ne) 0.0015%Helium (He) 0.0005%Methane (CH4) 0.00018%Ozone (O3) 0.000003–0.001%Krypton (Kr) 0.0001%
The atmosphereEquation of state and hydrostatic balance
The ocean
Temperature structureMajor constituentsGreenhouse gases
190 200 210 220 230 240 250 260 270 280 290 300Temperature [K]
200
400
600
800
1000
Pre
ssur
e [h
Pa]
Mean air temperature
NH high latitudes (60-90°N)NH mid latitudes (30-60°N)NH subtropics (15-30°N)Tropics (15°S-15°N)SH subtropics (15-30°SSH mid latitudes (30-60°S)SH high latitudes (60-90°S)
0.0 2.5 5.0 7.5 10.0 12.5 15.0
Specific humidity [g kg−1]
200
400
600
800
1000
Pre
ssur
e [h
Pa]
Mean atmospheric water vapor content
data from CFSR
Water Vapor
I a chemically active greenhouse gas
I critical for energy transport
I temperature determines upper limit
The atmosphereEquation of state and hydrostatic balance
The ocean
Temperature structureMajor constituentsGreenhouse gases
1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015Year
320
340
360
380
400
CO
2 co
ncen
tratio
n [p
pm]
Atmospheric CO2 at Mauna Loa
J F M A M J J A S O N D4
2
0
2
4
data from NOAA ESRL
Carbon Dioxide
I another important greenhouse gas
I primary source of carbon for photosynthesis
I affects ocean acidity
I well mixed
The atmosphereEquation of state and hydrostatic balance
The ocean
Temperature structureMajor constituentsGreenhouse gases
1985 1990 1995 2000 2005 2010Year
1600
1650
1700
1750
1800
1850
CH
4 co
ncen
tratio
n [p
pb]
Atmospheric CH4 (NOAA Marine Boundary Layer Reference)
data from NOAA ESRL
Methane
I also a greenhouse gas
I natural and anthropogenic sources
I important source of water vapor in the stratosphere
The atmosphereEquation of state and hydrostatic balance
The ocean
Temperature structureMajor constituentsGreenhouse gases
data from OMI
Ozone
I absorber of both solar and infrared radiation
I chemically active
I important for life, but harmful to health
The atmosphereEquation of state and hydrostatic balance
The ocean
The atmospheric equation of stateHydrostatic balance
p = ρRdT
Assumptions: I motion of air molecules is random
I individual molecules interact rarely
I air is dry: no water vapor
Atmospheric equation of state
The atmosphereEquation of state and hydrostatic balance
The ocean
The atmospheric equation of stateHydrostatic balance
0 200 400 600 800 1000Pressure [hPa]
0
20
40
60
80
100
Alti
tude
abo
ve s
ea le
vel [
km]
0 0.4 0.8 1.2Air density [kg m−3]
0
20
40
60
80
100
data from 1976 US Standard Atmosphere
The atmosphereEquation of state and hydrostatic balance
The ocean
The atmospheric equation of stateHydrostatic balance
pressure gradient force:
[p−
(dp
dz
)δz
]δA− pδA = −
(dp
dz
)δzδA
gravitational force: gρδAδz g = −(
1ρdpdz
)δz
δA
Hydrostatic balance
The atmosphereEquation of state and hydrostatic balance
The ocean
The atmospheric equation of stateHydrostatic balance
g = −1
ρ
dp
dz
ρ =p
RdT
hydrostatic balance
equation of state
scale heightdp
p= −dz
H, H =
RdT
g
If temperature is constant with height, then so is H:
p = pse(− z/H)
Applying hydrostatic balance
The atmosphereEquation of state and hydrostatic balance
The ocean
The atmospheric equation of stateHydrostatic balance
0 200 400 600 800 1000Pressure [hPa]
0
20
40
60
80
100
Alti
tude
abo
ve s
ea le
vel [
km]
0 0.4 0.8 1.2Air density [kg m−3]
0
20
40
60
80
100
p = pse(− z/H) ρ = p
RdT
data from 1976 US Standard Atmosphere
The atmosphereEquation of state and hydrostatic balance
The ocean
The atmospheric equation of stateHydrostatic balance
g = −1
ρ
dp
dz
m = ρdz
hydrostatic balance
mass of a layer
m =dp
g
The pressure at the top of the atmosphere is zero, so the mass per unit area is:
M =psrf − ptoa
g=psrf − 0
g=psrfg
Applying hydrostatic balance
The atmosphereEquation of state and hydrostatic balance
The ocean
CompositionEquation of stateVertical structure
constituent ion mass mixing ratio percentage ofin seawater [g kg−1] global salt
Chloride (Cl−) 19.215 54.96%Sodium (Na+) 10.685 30.58%
Sulphate (SO2−4 ) 2.693 7.70%
Magnesium (Mg2+) 1.287 3.69%Calcium (Ca2+) 0.410 1.17%Potassium (K+) 0.396 1.13%Bicarbonate (HCO−
3 ) 0.142 0.41%Bromide (Br−) 0.067 0.19%Boric acid (H3BO3) 0.026 0.07%
The atmosphereEquation of state and hydrostatic balance
The ocean
CompositionEquation of stateVertical structure
Equation of state for seawater
I pressure
I temperature
I density
I salinity
No general theory for liquids
Must be determined by fitting a function to measurements
The atmosphereEquation of state and hydrostatic balance
The ocean
CompositionEquation of stateVertical structure
0 250 500 750 1000 1250 1500 1750 2000Pressure [dbar]
0
500
1000
1500
2000
Dep
th [m
]
Mean pressure (World Ocean Atlas 2009)
NH high latitudes (60-90°N)NH mid latitudes (30-60°N)NH subtropics (15-30°N)Tropics (15°S-15°N)SH subtropics (15-30°SSH mid latitudes (30-60°S)SH high latitudes (60-90°S)
pressure increases at ∼1 atm per 10 m
data from WOA2009
The atmosphereEquation of state and hydrostatic balance
The ocean
CompositionEquation of stateVertical structure
5 0 5 10 15 20 25 30Temperature [°C]
0
500
1000
1500
2000
Dep
th [m
]
Mean temperature (World Ocean Atlas 2009)
NH high latitudes (60-90°N)NH mid latitudes (30-60°N)NH subtropics (15-30°N)Tropics (15°S-15°N)SH subtropics (15-30°SSH mid latitudes (30-60°S)SH high latitudes (60-90°S)
below 0◦C in high latitudes
thermocline
mixed layer
data from WOA2009
The atmosphereEquation of state and hydrostatic balance
The ocean
CompositionEquation of stateVertical structure
31 32 33 34 35 36Salinity [psu]
0
500
1000
1500
2000
Dep
th [m
]
Mean salinity (World Ocean Atlas 2009)
NH high latitudes (60-90°N)NH mid latitudes (30-60°N)NH subtropics (15-30°N)Tropics (15°S-15°N)SH subtropics (15-30°SSH mid latitudes (30-60°S)SH high latitudes (60-90°S)
data from WOA2009
The atmosphereEquation of state and hydrostatic balance
The ocean
CompositionEquation of stateVertical structure
σ(T, p, S) = ρ(T, p, S)− 1000kgm−3
generally report density relative to density of pure water:
Density of seawater
I pressure
I temperature
I salinity
The atmosphereEquation of state and hydrostatic balance
The ocean
CompositionEquation of stateVertical structure
20 22 24 26 28 30 32 34 36 38 40Density [kg m−3]
0
500
1000
1500
2000
Dep
th [m
]
Mean density (World Ocean Atlas 2009)
NH high latitudes (60-90°N)NH mid latitudes (30-60°N)NH subtropics (15-30°N)Tropics (15°S-15°N)SH subtropics (15-30°SSH mid latitudes (30-60°S)SH high latitudes (60-90°S)
data from WOA2009
The atmosphereEquation of state and hydrostatic balance
The ocean
CompositionEquation of stateVertical structure
20 21 22 23 24 25 26 27 28 29 30Potential density [kg m−3]
0
500
1000
1500
2000
Dep
th [m
]
Mean potential density (World Ocean Atlas 2009)
NH high latitudes (60-90°N)NH mid latitudes (30-60°N)NH subtropics (15-30°N)Tropics (15°S-15°N)SH subtropics (15-30°SSH mid latitudes (30-60°S)SH high latitudes (60-90°S)
mixing depends on vertical gradient
data from WOA2009