Climate & Climatic Variation (Chapter 2). CLIMATE = 1. Statistics of Weather Daily Precipitation -...
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Transcript of Climate & Climatic Variation (Chapter 2). CLIMATE = 1. Statistics of Weather Daily Precipitation -...
Climate & Climatic VariationClimate & Climatic Variation
(Chapter 2)(Chapter 2)
CLIMATE =CLIMATE =
1. Statistics of Weather1. Statistics of Weather
Daily Precipitation - Iowa/Nebraska
CLIMATE =CLIMATE =
1. Statistics of Weather1. Statistics of Weather
2.2. The expected weather + The expected weather + departures from expected departures from expected weatherweather
CLIMATE CLIMATE
Reflects the geophysical processes active at Reflects the geophysical processes active at a location…a location…
Northeastern Siberia
Namibia
Amazon
Rainforest
CLIMATE =CLIMATE =
……and how they might change (e.g., seasonally)…and how they might change (e.g., seasonally)…
Winter Daily Precipitation - Iowa/Nebraska
CLIMATE =CLIMATE =
Summer Daily Precipitation - Iowa/Nebraska
……and how they might change (e.g., seasonally)…and how they might change (e.g., seasonally)…
… and in the future! (and of course the past)
CLIMATECLIMATE
1.1. Implies samples over a period of time. Implies samples over a period of time. How long? How frequent?How long? How frequent?
2. WMO standard: 30 years2. WMO standard: 30 years
- which 30?which 30?
- paleoclimate?paleoclimate?
3. There is no universal standard, but 3. There is no universal standard, but mustmust define the interval for the topic at handdefine the interval for the topic at hand
CLIMATECLIMATE
1.1. Has regular cycles …Has regular cycles …
CyclesCycles - Net Radiation
FSHFLH
FLH
- Net Radiation
FSH
Grassland
Dry Lake
Diurnal
CyclesCycles
Annual
Soil Temperature at depths marked
CLIMATECLIMATE
1.1. Has regular cycles …Has regular cycles …
2.2. … … with other types of variability with other types of variability superimposed …superimposed …
Climatic Variation and ChangeClimatic Variation and Change
(IPCC TAR, Ch. 2)
Note: Note: Trends, Abrupt Change, StationarityTrends, Abrupt Change, Stationarity
Climatic Variation and ChangeClimatic Variation and Change
(IPCC TAR, Ch. 2)
Note: Note: Quasi-periodicQuasi-periodic
Increased range of variabilityIncreased range of variability
Climatic Variation and ChangeClimatic Variation and Change
Additional FactorsAdditional Factors
1.1. Abrupt changeAbrupt change- external conditions (e.g., solar output)external conditions (e.g., solar output)
- internal feedbacksinternal feedbacks
- passing a threshold (e.g. ice caps passing a threshold (e.g. ice caps melting)melting)
2. Multiple climate states from the same 2. Multiple climate states from the same external conditionsexternal conditions
The Climate SystemThe Climate System
(IPCC TAR, Ch. 1)
The Climate SystemThe Climate System
(IPCC TAR, Ch. 1)
The Climate SystemThe Climate System
Three important controling factors:Three important controling factors:
1.1. LatitudeLatitude
- insolation- insolation
2.2. ElevationElevation
- temp. decrease with height- temp. decrease with height
3.3. Closeness to oceansCloseness to oceans
- heat reservoir- heat reservoir
The Climate SystemThe Climate System
(Peixoto & Oort, 1992)
Water in the climate system:Water in the climate system:
The Climate SystemThe Climate System
The Climate SystemThe Climate System
Mean extreme temperatures and differences (˚C) :Mean extreme temperatures and differences (˚C) :
Northern Hemisphere
8.0
(Jan)
21.6
(Jul)
13.6
Southern Hemisphere
10.6
(Jul)
16.5
(Jan)
6.5
Globe 12.3
(Jan)
16.1
(Jul)
3.9
Thermal Inertia of OceansThermal Inertia of Oceans
Annual Temperature Range
(Wallace & Hobbs, 1979)
The Climate SystemThe Climate System
(Michael Pidwirny, DLESE, 2004)
The Climate SystemThe Climate SystemSubsystemsSubsystems
1.1. AtmosphereAtmosphere
- rapid changes- rapid changes
- links other subsystems- links other subsystems
- greenhouse gases - greenhouse gases
2.2. OceanOcean
- slow evolution (“memory”, “flywheel”)slow evolution (“memory”, “flywheel”)
- chemical role, esp. COchemical role, esp. CO22
3.3. LandLand
- range of time scales- range of time scales
- cryosphere & biosphere roles- cryosphere & biosphere roles
- location of continents- location of continents
CryosphereCryosphere
Area
(106 km2)
Sea-lev. equiv. (m)
Max extent (%)
Min extent (%)
N.H.Land snow & ice 2.2
(Grnl: 1.7)
7.8
Sea ice 8.9
Total 11.0 24 % (Feb) 4 % (Aug)
S.H.Land snow & ice 13.0
(Antr: 13)
73.5
Sea ice 4.2
Total 17.2 13 % (Oct) 7 % (Feb)
Note: Note: Time scales, albedo effectsTime scales, albedo effects
BiosphereBiosphere
Note: albedo, evapotranspiration, surface roughness, gas exchanges (esp. CONote: albedo, evapotranspiration, surface roughness, gas exchanges (esp. CO22))
Feedbacks
Internal couplings through linking processes
Amplify or diminish initial induced climate change
Negative Feedback: Example
How does Earth’s temperature get established and maintained?
Solar ConstantSolar Constant
At photosphere surface, At photosphere surface, solar flux ~ 6.2solar flux ~ 6.2..101077 W-m W-m-2-2
Solar ConstantSolar Constant
At Earth’s orbit, solar flux ~ 1360 W-mAt Earth’s orbit, solar flux ~ 1360 W-m-2-2
At photosphere surface, At photosphere surface, solar flux ~ 6.2solar flux ~ 6.2..101077 W-m W-m-2-2
Planetary AlbedoPlanetary Albedo
Scattering: air molecules, aerosols Reflection: clouds
Surface albedo
What is Earth’s temperature?What is Earth’s temperature?
Balance: Radiation in = Radiation outBalance: Radiation in = Radiation out
Incoming = 1360 W-m-2 x (1-albedo) x (area facing sun) = 1360 x (1-0.3) x a2
= 1.2.10+17 W
a
What is Earth’s temperature?What is Earth’s temperature?
Balance: Radiation in = Radiation outBalance: Radiation in = Radiation out
Incoming = 1360 W-m-2 x (1-albedo) x (area facing sun) = 1360 x (1-0.3) x a2
= 1.2.10+17 W
a
Outgoing = T4 x (area emitting) ; i.e., black body = T4 x 4 a2
What is Earth’s temperature?What is Earth’s temperature?
Balance: Radiation in = Radiation outBalance: Radiation in = Radiation out
Incoming = 1360 W-m-2 x (1-albedo) x (area facing sun) = 1360 x (1-0.3) x a2
= 1.2.10+17 W
a
Balance implies T = {0.71360 W-m-2)/4}1/4 = 255 K = -18 oC
Outgoing = T4 x (area emitting) ; (i.e., black body) = T4 x 4 a2
What is Earth’s temperature?What is Earth’s temperature?
Balance: Radiation in = Radiation outBalance: Radiation in = Radiation out
Difference? Must account for atmosphere (greenhouse effect).
a
Balance implies T = -18 Balance implies T = -18 ooCCObserved surface T = +15 Observed surface T = +15 ooCC
What if temperature decreases?What if temperature decreases?
The same:Incoming = 1.2.10+17 WOutgoing = T4 x (area emitting) = T4 x 4 a2
a
What if temperature decreases?What if temperature decreases?
~ Negative Feedback ~~ Negative Feedback ~
These are the same:Incoming = 1.2.10+17 WOutgoing = T4 x (area emitting) = T4 x 4 a2
a
But for T < 255 K: imbalance Incoming solar exceeds outgoing IR net energy input T increases
Negative Feedback
1. Perturb climate system
2. Negative feedback moves climate back toward starting point
3. A stabilizing factor
Positive Feedback: Example
How does Earth’s temperature get established and maintained?
Greenhouse EffectGreenhouse Effect
IR radiation absorbed & re-emitted, partially toward surface
Solar radiation penetrates
Greenhouse EffectGreenhouse Effect
IR radiation absorbed & re-emitted, partially toward surface
Emitted IR: ~200-500 W-mEmitted IR: ~200-500 W-m
Net IR: ~25-100 W-mNet IR: ~25-100 W-m
Greenhouse EffectGreenhouse Effect
Cooler atmosphere: - Less water vapor - Less IR radiation absorbed & re-emitted
Solar radiation penetrates
Greenhouse EffectGreenhouse Effect
Cooler atmosphere: - thus less surface warming - cooler surface temperature
Solar radiation penetrates
Positive Feedback
1. Perturb climate system
2. Positive feedback moves climate away from starting point
3. A destabilizing factor
Other examples (textbook):
- ice-albedo feedback
- CO2-ocean temperature feedback
Feedbacks
Distinguish between:
1. external forcing change
- e.g., insolation, volcanism
- often predictable
2. Internal feedback mechanisms
- nonlinear, coupled interactions
- generally less predictable (stochastic)
Black Body Curves
6,000 K 255 K
Em
issi
on
Wavelength []
Solar
(shortwave, visible)
Terrestrial
(longwave, infrared)
Radiation SpectrumRadiation Spectrum
Daily Daily Solar Solar
Radiation Radiation at Top of at Top of Atmos.Atmos.
[106 J-m-2]
Earth’s mean annual Earth’s mean annual radiation and energy balanceradiation and energy balance
Absorbed Solar RadiationAbsorbed Solar Radiation
Outgoing Terrestrial RadiationOutgoing Terrestrial Radiation
Key Energy Fluxes at SurfaceKey Energy Fluxes at Surface
Sensible Heat
Tair
FSH = Cp(wT)s
FSH ≈ - CpCH(Tair-Ts)
CH = CH(V, zo, d/dz)
Ts
Surface Sensible Heat FluxSurface Sensible Heat Flux
(Peixoto & Oort, 1992)
Latent Heat
FLH ~ - CpCW{eair-esat(Ts)}
CW = CW(V, zo, d/dz)
but also
CW = CW(physiology)
soil moisture
CW leaf temp.
sunlight
CO2 level
Key Key Energy Energy Fluxes at Fluxes at SurfaceSurface
Surface EvaporationSurface Evaporation
(Peixoto & Oort, 1992)
CyclesCycles - Net Radiation
FSHFLH
FLH
- Net Radiation
FSH
Grassland
Dry Lake
Diurnal
Less cooling by evaporation
Ts increases
FSH larger
Role of AlbedoRole of Albedo
Scattering: air molecules, aerosols Reflection: clouds
Surface albedo
Ocean 2-6%Snow 40-95%Crop 15-25%Forest 5-10%Cities 14-18%
Role of AlbedoRole of Albedo
Albedo changes with latitudeAlbedo changes with latitude- changing land surface- changing land surface- changes in incidence angle- changes in incidence angle
Albedo changes with timeAlbedo changes with time- land changes (e.g., ice sheets)- land changes (e.g., ice sheets)- cloud cover- cloud cover
Role of AlbedoRole of Albedo
Albedo changes with latitudeAlbedo changes with latitude
Role of Greenhouse GasesRole of Greenhouse Gases
Primary gases: Primary gases: water vapor,water vapor, CO CO22, methane (CH, methane (CH44), nitrous oxide (N), nitrous oxide (N22O), ozone (OO), ozone (O33))
Time Scales of Climatic VariationTime Scales of Climatic Variation
(IPCC TAR, Ch. 2)Note: Note: Magnitude of changesMagnitude of changes
Reduced “detectability” farther back in timeReduced “detectability” farther back in time
(IPCC TAR, Ch. 2)
Different size of changesDifferent size of changes
Time Scales of Climatic VariationTime Scales of Climatic Variation
Time Scales of Climatic VariationTime Scales of Climatic Variation
Earth’s Orbital ParametersEarth’s Orbital Parameters
Perihelion(~ Jan 3)
Vernal Equinox (~ March 21)
Aphelion(~ July 5)
Earth’s Orbital ParametersEarth’s Orbital Parameters
Eccentricity = SQRT(a2 - b2)/a ; for circle, = 0
Longitude of perihelion (one choice: angle from NH vernal equinox)
Tilt of rotation axis (obliquity)
b
a
Variability of Earth’s Orbital ParametersVariability of Earth’s Orbital Parameters
Earth’s Orbital ParametersEarth’s Orbital Parameters
Periodic variations
Current Range ~ Period (yr.)
Eccentricity: ~ 0.02 [0.0 - 0.05] 95,800
Longitude of perihelion ~ 270˚ [0˚ - 360˚] 21,700
Obliquity 23.4˚ [21.8˚ - 24.4˚] 41,000
b
a
Earth’s Orbital ParametersEarth’s Orbital Parameters
Seasonal efffect of variations (little annual effect)
Eccentricity: intensity of seasons
Longitude of perihelion NH-SH differences in summer insolation
Obliquity extratropical summer-winter differences
b
a
Variability of Earth’s Orbital ParametersVariability of Earth’s Orbital Parameters
Changes in Earth’s OrbitChanges in Earth’s Orbit
Some paleo-records can resolve different Some paleo-records can resolve different frequencies in an orbital element’s variability frequencies in an orbital element’s variability (e.g., 19,000 and 23,000 yr periods in (e.g., 19,000 and 23,000 yr periods in precession).precession).
Some can detect “beat” frequencies.Some can detect “beat” frequencies.
Relative importance of frequencies changes Relative importance of frequencies changes with time - and may not correspond to dominant with time - and may not correspond to dominant frequencies in climatic response.frequencies in climatic response.
Shorter, lower amplitude frequencies might be Shorter, lower amplitude frequencies might be important for decadal-millenial climate changes.important for decadal-millenial climate changes.
Changes in Earth’s OrbitChanges in Earth’s Orbit
Changes in Earth’s orbit affect Changes in Earth’s orbit affect - annual insolation cycle- annual insolation cycle- past glacial-interglacial variability- past glacial-interglacial variability
Croll (late 1800s)Croll (late 1800s)
Milankovitch (1941)Milankovitch (1941)
Berger (1970s)Berger (1970s)
Changes in Earth’s OrbitChanges in Earth’s Orbit
Changes in Earth’s orbit affect Changes in Earth’s orbit affect - annual insolation cycle- annual insolation cycle- past glacial-interglacial variability- past glacial-interglacial variability
Optimum conditions: Optimum conditions: minimum obliquity, high minimum obliquity, high eccentricity, aphelion during NH summereccentricity, aphelion during NH summer
- allow snow to persist through summer- allow snow to persist through summer- allow relatively warm winter (increased - allow relatively warm winter (increased subtropical evap. & increased snowfall)subtropical evap. & increased snowfall)- transition seasons may also be important - transition seasons may also be important for snow-cover expansionfor snow-cover expansion
Variability of Earth’s Orbital ParametersVariability of Earth’s Orbital Parameters
Milankovitch TheoryMilankovitch Theory
GlobalRegional Regional Regional Regional
Microscale Microscale Microscale Microscale Microscale Microscale Microscale Microscale Microscale
Pla
nt A
Crop BCrop A
Inse
ct A
Soi
l Pat
hoge
n B
Air-TransportedPathogen A
Field Field Field Field Field Field Field Field Field Field
Regional Regional Regional Regional
Continental
Hydrology, Soil Microbiology, Soil Biochemistry
Soil AH2O, temperature,
nutrients, microbes, soil carbon, trace chemicals
Soil AH2O, temperature,
nutrients, microbes, soil carbon, trace chemicals
Soil BH2O, temperature,
nutrients, microbes, soil carbon, trace chemicals
Soil BH2O, temperature,
nutrients, microbes, soil carbon, trace chemicals
Soil CH2O, temperature,
nutrients, microbes, soil carbon, trace chemicals
Scales of Climate
Scales of Landforms
Soi
l Pat
hoge
n D
Pla
nt B
Inse
ct B
Air-TransportedPathogen B
Human Influences
Management Management
Che
mic
als
Ero
sion
Che
mic
als
Surf
ace
s lop
e, I
R R
adi a
t ion
, Eva
pora
t ion
, Bio
geoc
hem
i cal
s
Detritus
Particulate D
eposition, Precipitation, S
olar Radiation, IR
Microclimate A
Sol
ar, I
R, w
ind,
CO
2, C
O, N
Ox,S
O2,
H2O
, tem
pera
ture
,
trac
e ga
ses,
shad
ing,
pa
rtic
ulat
e m
atte
r
Sol
ar, I
R, w
ind,
CO
2, C
O, N
Ox,S
O2,
H2O
, tem
pera
ture
,
trac
e ga
ses,
shad
ing,
pa
rtic
ulat
e m
atte
r
Sol
ar, I
R, w
ind,
CO
2, C
O, N
Ox,S
O2,
H2O
, tem
pera
ture
,
trac
e ga
ses,
shad
ing,
pa
rtic
ulat
e m
atte
r
Microclimate CMicroclimate B
ChemicalsChem
icals
Climate & Climatic VariationClimate & Climatic Variation
(Chapter 2)(Chapter 2)
ENDEND