GEOG 445
Climatology
Introduction to the
Climate System
What is climate?
Climate refers to mean characteristics of quantities such as
temperature and precipitation at the surface.
- there are good reasons for that...
-
GEOG 445: Climatology
Axel Kleidon
What is climate?
-90
-60
-30
0
30
60
Annual Mean Temperature
90
-180
-120
-60
-30
0
60
-20
-10
0
10
20
Annual Mean Temperature (°C)
120
180
30
Source: Cramer and Leemans (pers. comm.)
GEOG 445: Climatology
Axel Kleidon
What is climate?
-90
-60
-30
0
30
60
Annual Mean Precipitation
90
-180
-120
-60
0
0
500
1000
1500
Annual Precipitation (mm)
60
120
180
2000
Source: Cramer and Leemans (pers. comm.)
GEOG 445: Climatology
Axel Kleidon
What is climate?
-90
-60
-30
0
30
60
Activity of the Land Biota
90
-180
-120
-60
0.0
0
0.2
0.4
0.6
Average FPAR
60
0.8
120
180
1.0
Source: ISLSCP
GEOG 445: Climatology
Axel Kleidon
What is climate?
-90
-60
-30
0
30
60
Annual Temperature Range
90
-180
-120
-60
0
0
60
10
20
30
40
Annual Temperature Range (K)
120
180
50
Source: Cramer and Leemans (pers. comm.)
GEOG 445: Climatology
Axel Kleidon
What is climate?
-90
-60
-30
0
30
60
Annual Precipitation Range
90
-180
-120
-60
0
50
0
60
100
150
200
Precipitation Range (mm)
120
180
250
Source: Cramer and Leemans (pers. comm.)
GEOG 445: Climatology
Axel Kleidon
What is climate?
-90
-60
-30
0
30
60
Seasonality in Activity of Land Biota
90
-180
-120
-60
0.00
0
0.25
0.50
0.75
Max. FPAR - Min. FPAR
60
120
180
1.00
Source: ISLSCP
GEOG 445: Climatology
Axel Kleidon
What is climate?
Connection to vegetation types
Source: Atlas of the Biosphere, atlas.sage.wisc.edu
GEOG 445: Climatology
Axel Kleidon
What is climate?
Connection with Plant Species Richness
Source: Barthlott et al. 1996
GEOG 445: Climatology
Axel Kleidon
What is climate?
- Mean atmospheric surface variables (e.g. temperature,
precipitation) show clear geographic and seasonal patterns
- These patterns are reflected in the spatial variations of
biotic functioning (light absorption, vegetation type,
diversity)
- Climate: predictable aspects of atmospheric characteristics
GEOG 445: Climatology
Axel Kleidon
What is climate?
Climate typically refers to a particular time-scale:
Time scale
Term
Hours
Diurnal (Night/Day)
Days
Synoptic
Months
Seasonal
Years
Interannual
Climatic Variability
10’s of Years
Interdecadal
Climate
Hundreds of Years
GEOG 445: Climatology
Weather
Climatic Change
Axel Kleidon
What is climate?
Peixoto
andClimatology
Oort: Physics of Climate
GEOG 445:
Axel Kleidon
What is climate?
Climatology:
- understand the processes and interactions which lead to the
geographic and seasonal variation of climate
GEOG 445: Climatology
Axel Kleidon
The Climate System
TODAY:
atmospheric structure
and composition
atmosphere
ice
ice
ocean
GEOG 445: Climatology
Hartmann, Figure 1.2
land
NEXT:
ocean, ice, land
Axel Kleidon
Atmosphere: Structure
Lapse Rate !
defined as the decrease of temperature T with height z:
"
Γ=−
dT
dz
"
typical values are 6-8 K/km, mean is 6.5 K/km
"
result of “radiative-convective” equilibrium (more later…)
GEOG 445: Climatology
Axel Kleidon
Hartmann, Figure 1.3
Atmosphere: Structure
!
- Exponential decrease of pressure with height reflects hydrostatic
balance
- balance of gravity force with pressure gradient force
- increase of pressure dp of a parcel of thickness dz:
dp = ρ · g · dz
top of
atmosphere
dz
p=0
some atmospheric mass
atmospheric mass = ! g
p(z − dz) = p(z) − dp
p(z)
more atmospheric mass
surface
ps
GEOG 445: Climatology
Axel Kleidon
Atmosphere: Structure
!
results in a decrease of pressure p with height z (which depends
on density !)
dp
= −ρ · g
dz
what about density?
GEOG 445: Climatology
Axel Kleidon
Atmosphere: Structure
!
Ideal Gas Law relates density to pressure p and temperature T:
p = ρRT
... and some transformations, we get a differential equation:
g
dp
= −ρg = −
p
dz
RT
" … if we assume T = const, the solution is given by:
p = ps · e−z/H
H=
g
RT
GEOG 445: Climatology
Axel Kleidon
If you are standing atop
Mount Everest at 8848m,
about what fraction of
mass of the atmosphere is
below you?
Hartmann, Figure 1.8
Question
* If the atmosphere warmed up by 5°C, would the atmospheric
pressure at 5km above sea level increase or decrease? By
approximately how much?
GEOG 445: Climatology
Axel Kleidon
Atmosphere: Structure
Summary:
- atmospheric layers: troposphere, stratosphere, …
- lapse rate: change of temperature with height
- hydrostatic balance results in exponential drop in pressure
GEOG 445: Climatology
Axel Kleidon
Atmosphere: Composition
Constituent
Formula
Mol weight
Conc. by
volume
Nitrogen
N2
28.013
78.08%
3.9*1021
Oxygen
O2
31.999
20.95%
1.2*1021
Argon
Ar
39.948
0.934%
6.6*1019
H2O
Water vap.
Carbon dioxide CO2
18.015
44.01
Variable
1.7*1019
2.8*1018
Neon
Krypton
Ne
Kr
20.183
83.80
18.2 ppmv
1.14 ppmv
6.5*1016
1.7*1016
Helium
He
4.00
5.24 ppmv
Methane
CH4
16.04
1.72 ppmv
3.7*1015
4.9*1015
0.0353%
(353 ppmv)
Total mass
(g)
based on Hartmann, Table 1.1
GEOG 445: Climatology
Axel Kleidon
Atmosphere: Composition cont.
Constituent
Formula
Xenon
Xe
Ozone
O3
Nitrous oxide
N2O
Carbon
monoxide
Mol weight
131.3
Conc. by
volume
87 ppbv
Total mass
(g)
2.0*1015
48.0
variable
3.3*1015
44.0
310 ppbv
2.3*1015
CO
28.0
120 ppbv
5.9*1014
Hydrogen
H2
2.0
500 ppbv
1.8*1014
Ammonia
NH3
17.0
100 ppbv
3.0*1013
Nitrogen
dioxide
NO2
46.0
1 ppbv
8.1*1012
CFC-11
CCl2F2
120.9
480 pptv
1.0*1013
based on Hartmann, Table 1.1
GEOG 445: Climatology
Axel Kleidon
Composition and Global Cycles
Atmospheric composition of chemical elements is the
reflection of biogeochemical fluxes and cycles
one characteristic is the residence time "
change in atmospheric mass dm/dt
m
dm
= Fin −
dt
τ
influx
Fin
outflux
Fout = - m/!
GEOG 445: Climatology
Axel Kleidon
Concentration and Residence Time
Steady-state concentration defined by Fin = Fout
residence time describes characteristic time that a molecule
spends in the reservoir
τ=
m
m
=
Fin
Fout
What are the
consequences of different
residence times for spatial and
temporal variability?
GEOG 445: Climatology
Axel Kleidon
Example: Present-Day Carbon Cycle
Residence
time of atmospheric atmosphere: 750 GtC
CO2 ?
90 GtC/yr
60 GtC/yr
plants: 500 GtC
soils: 1,500 GtC
ocean: 38,000 GtC
GtC = Gigatons of Carbon = 1012 kgC
GEOG 445: Climatology
Axel Kleidon
Variations of “Precipitable Water”
0
50
GEOG 445: Climatology
Axel Kleidon
Example: Global Water Cycle
Residence
time of atmospheric
H2O ?
361
atmosphere: 13
37
324
99
62
ice: 22,780
soils: 225
37
ocean: 1,348,000
ground water: 8,062
all fluxes in 1012 m3/yr
GEOG 445: Climatology
Axel Kleidon
Variations of atmospheric CO2
380
340
GEOG 445: Climatology
Axel Kleidon
Catling (2004)
Atmosphere: Composition
Evolution of atmospheric composition:
- Emphasizes importance of biosphere on long time scales
- Substantially impacted the atmospheric greenhouse effect (more
next week)
GEOG 445: Climatology
Axel Kleidon
Question
* Early Earth likely had a strong CO2 greenhouse. Where did all
the carbon go?
GEOG 445: Climatology
Axel Kleidon
Atmosphere: Composition
Summary:
- Most of the atmosphere consists of inert gases (they do not
react without addition of energy)
- Gases of particular importance:
- Greenhouse gases (absorb terrestrial radiation), e.g.
CO2, CH4, N2O, CO
- Oxygen (O2 and O3, largely of biotic origin, reactive,
absorbs ultraviolet radiation)
- Manmade compounds (CFC-11; CFC-12; SF6)
GEOG 445: Climatology
Axel Kleidon
Next Class
for next class:
prepare: read chapter 1
bring questionnaire, questions, comments
bring your 3 favorite choices from list of topics
GEOG 445: Climatology
Axel Kleidon