with climate variability and change Seminar in Atmospheric Science EESC G9910 Diagnosing ENSO from atmospheric composition ozone measured from space Ziemke et al 2010 Oman et al 2011 ID: 168367
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Slide1
Connecting atmospheric composition with climate variability and change Seminar in Atmospheric Science, EESC G9910
Diagnosing ENSO from atmospheric composition (ozone measured from space)
Ziemke
et al
., 2010;
Oman et al
., 2011
To be discussed
Week 4Slide2
Course InformationTwo motivating questions:How does climate variability (and change) influence distributions of trace species in the troposphere?How do changes in trace species alter climate?Email me by Monday Sept 10:
a) to sign up for presentation:
amfiore
@
ldeo.columbia.edu
b) Credit options:
1 point (discussion only)
2 points (discussion + presentation)
Weekly readings at
www.ldeo.columbia.edu
/~
amfiore
/eescG9910.htmlSlide3
Today’s OutlineOverview of composition-climate interactionsIntro to key concepts a. Units of atmospheric composition b. Budgets / Lifetimes c. Radiative ForcingSlide4
Big Issues in Atmospheric Chemistry
LOCAL
< 100 km
REGIONAL
100-1000 km
GLOBAL
> 1000 km
Urban smog
Point source
Disasters
Visibility
Regional smog
Acid rain
Ozone
layer
Climate
Biogeochemical cycles
Daniel JacobSlide5
From Brasseur & Jacob,Ch2, draft chapterJan 2011 version; Text in prepSlide6
Air pollutants affect climate; changes in climate affect global atmospheric chemistry (and regional air pollution)NMVOCsCO, CH4
NO
x
pollutant sources
+
O
3
+
OH
H
2
O
Black carbon
Sulfate
organic carbon
T
T
Aerosols interact with sunlight
“direct” + “indirect” effects
Surface of the Earth
Greenhouse gases
absorb infrared radiation
T
atmospheric cleanser
Smaller droplet size
clouds last longer
increase
albedo
less precipitation
A.M. FioreSlide7
Climate (change) affects chemistry (and air quality)
sources
strong
mixing
(1)
Transport / mixing (e.g., distribution of trace species)
Exchange with stratosphere
(3) Chemistry responds to changes in temperature, humidity
NMVOCs
CO, CH
4
NO
x
+
O
3
+
OH
H
2
O
PAN
(2) Emissions (biogenic, lightning NO
x
, fires)
VOCs
Planetary boundary layer
tropopause
A.M. FioreSlide8
1.1 Mixing ratio or mole fraction CX [mol mol-1]
remains constant when air density changes
e
robust measure of atmospheric composition
SPECIES
MIXING RATIO
(dry air)
[mol
mol
-1
]
Nitrogen (N
2
)
0.78
Oxygen (O
2
)
0.21
Argon (Ar)
0.0093
Carbon dioxide (CO
2
)
380x10
-6Neon (Ne)
18x10-6
Ozone (O3)(0.01-10)x10-6
Helium (He)
5.2x10
-6
Methane (CH
4)
1.7x10-6Krypton (Kr)
1.1x10-6
Trace
gases
Air also contains variable H
2
O vapor (10
-6
-10
-2
mol mol
-1
) and aerosol particles
Trace gas concentration units:
1 ppmv = 1 µmol mol
-1
= 1x10
-6
mol mol
-1
1 ppbv = 1 nmol mol
-1
= 1x10
-9
mol mol
-1
1 pptv = 1 pmol mol
-1
= 1x10
-12
mol mol
-1
Daniel JacobSlide9
1.2 Number density nX [molecules cm-3]
Proper measure for
reaction rates
optical properties of atmosphere
Proper measure for absorption or scattering of radiation by atmosphere
n
X
and
C
X
are related
by the ideal gas law:
Also define the mass concentration (g cm
-3
):
n
a
= air density
A
v
= Avogadro
’s numberP = pressureR = Gas constantT = temperature
MX= molecular mass of XDaniel JacobSlide10
ATMOSPHERIC BUDGET TERMS GLOBAL SOURCE: emissions, in situ production (Tg yr-1)
well-known for some (well-documented) synthetic gases
GLOBAL SINK: chemical destruction, photolysis, deposition (
Tg
yr
-1
)
ATMOSPHERIC BURDEN: total mass (
Tg
) integrated over the atmosphere Well known (measurements) for long-lived (well-mixed) gases Poorly constrained for short-lived species TREND: difference between sources and sinks (Tg yr-1)
More detail: TAR 4.1.3 Slide11
Recent trends in well-mixed GHGshttp://www.esrl.noaa.gov/gmd/aggi/Slide12
More than half of global methane emissions
are influenced by human activities
~300 Tg CH
4
yr
-1
Anthropogenic [EDGAR 3.2 Fast-Track 2000;
Olivier et al
., 2005]
~200 Tg CH
4
yr
-1 Biogenic sources [Wang et al., 2004] >25% uncertainty in total emissions
ANIMALS
90
LANDFILLS +
WASTEWATER
50
GAS + OIL
60
COAL
30
RICE 40
TERMITES
20WETLANDS180
BIOMASS BURNING + BIOFUEL 30GLOBAL METHANE
SOURCES (Tg CH4 yr-1)
PLANTS?
60-240 Keppler et al., 2006
85 Sanderson et al., 2006
10-60 Kirschbaum et al., 2006
0-46 Ferretti et al., 2006
Clathrates?
Melting permafrost?
A.M. FioreSlide13
LifetimesAtmospheric Lifetime: Amount of time to replace burden (turnover time) t (yr) = burden (Tg
) / mean global sink (Tg yr
-1
)
for a gas in steady-state (unchanging burden; sources = sinks
Convenient scale factor:
(1) constant emissions (
Tg
/yr) steady-state burden (Tg) (2) emission pulse (Tg) time integrated burden of that pulse (Tg/yr)Perturbation (
e-folding) Time – can differ from the atmospheric steady-state lifetime only equal to atmospheric lifetime for gases with constant chemical lifetime (e.g., Rn, radioactive decay) Chemical feedbacks (e.g., CH4: more CH4, longer CH4 lifetime; N2O: more N2O, shorter lifetimeLifetimes can vary spatially and temporally -- species with lifetimes shorter than mixing time scales (< 1 year)(TAR 4.1.4)Slide14
TIME SCALES FOR HORIZONTAL TRANSPORT(TROPOSPHERE)
2 weeks
1-2 months
1-2 months
1 year
c/o Daniel JacobSlide15
TYPICAL TIME SCALES FOR VERTICAL MIXING
0 km
2 km
1 day
planetary
boundary
layer
tropopause
5 km
(10 km)
1 week
1 month
10 years
c/o Daniel JacobSlide16
Radiative Forcing (RF): A convenient metric for comparing climate responsesto various forcing agentsRF = Change in net (down-up) irradiance (radiative flux) at the tropopause
due to a perturbation to an atmospheric constituent
D
T
s
=
l *
RF
Climate
s
ensitivityparameterGlobal, annual mean change in surface T in responseto RF (equilibrium)Why is this convenient/useful ? First order estimate, best for LLGHGsRelatively easy to calculate (as opposed to climate response)Related to global mean equilibrium T change at surface:Slide17
uv
vis
near-ir
longwave
Methane
Nitrous oxide
Oxygen; Ozone
Carbon dioxide
Water vapor
Solar
blackbody
fn.
Earth’s
“effective”
blackbody fn.
CFCs
Clouds,
Aerosols
active
throughout
spectra
c/o V. RamaswamySlide18
IR Transmission/Absorption in/near atmospheric windowFrom Jan 2012 version Ch 5 of Brasseur & Jacob textbook in prepSlide19
Radiative Forcing: Analytical expressions for Well-mixed GHGsFrom IPCC TAR CH6, Table 6.2http://www.esrl.noaa.gov/gmd/aggi/Slide20
Radiative Forcing (RF): comparison of calculation methodologiesFigure 2.2, WG1 IPCC AR-4 Chapter 2, Section 2.2Slide21
Radiative forcing of climate (1750 to present):Important contributions from non-CO2 species
IPCC,
2007Slide22
Global Warming PotentialsRadiative forcing does not account for different atmospheric lifetimes of forcing agentsGWP attempts to account for this by comparing the integrated RF over a specified period (e.g. 100 years) from a unit mass pulse emission, relative to CO2.Slide23
WHAT IS THE ATMOSPHERE?
Gaesous envelope surrounding the Earth
Mixture of gases, also contains suspended solid and liquid particles (
aerosols)
Aerosol = dispersed condensed phase suspended in a gas
Aerosols are the
“
visible
”
components of the atmosphere
The atmosphere seen from space
Pollution off U.S. east coast
Dust off West Africa
California fire plumes
Daniel JacobSlide24
ATMOSPHERIC GASES ARE “VISIBLE” TOO…IF YOU LOOK IN THE UV OR IR
Nitrogen dioxide (NO
2
) observed by satellite in the UV
Daniel Jacob