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Investigating Links between Atmospheric Chemistry, Climate, and the Biosphere

Loretta J. Mickley, 4 November 2011

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with Amos Tai, Lee Murray, Xu Yue, Jennifer Logan, Daniel Jacob, Shiliang Wu, Eric Leibensperger, Dominick Spracklen

Wildfires in Quebec, May 31, 2010

Haze over Boston on the same day

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Atmospheric chemistry examines the mix of gases and particles in the atmosphere. Our group mainly focuses on short-lived species: ozone, particles, mercury and their precursors, with lifetimes days to weeks.

Lifetimes in atmospheric chemistry

Centuries: SF6, some CFCs

Decades: most greenhouse gases: CO2, N2O, . . .

9-10 years: CH4 (methane, precursor to ozone and greenhouse gas)

Days-weeks: O3 (ozone), particulate matter (PM)

Seconds: OH, NO

Pollution over Hong Kong

Air pollution over Hong Kong reached dangerous levels one of every eight days in 2009

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Surface ozone and particulate matter are harmful to human health.

EPA’s Technical Support Document for the proposed finding on CO2 as a pollutant.Cites the threat of climate change to air quality

Calculated with standard of 0.075 ppm. Proposed new standards will push more areas into non-attainment.

Number of people living in areas that exceed the national ambient air quality standards (NAAQS) in 2008.

Short-lived species respond to climate change as well as to trends in emissions.

2009

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Surface ozone and particulate matter also affect climate.

Radiative forcing W m-2

ozone

visibleinfra- red

Many particles scatter incoming sunlight (cooling). Ozone absorbs outgoing terrestrial radiation (warming)

particles

IPCC 2007

Yardstick of warming or cooling effect

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O3

O2 hn

O3

Deposition

STRATOSPHERE

TROPOSPHERE

8-18 km

Lifecycle of tropospheric ozone: production is via oxidation of CO, VOCs, and methane in the presence of NOx.

NOx

• Nonmethane volatile organic compounds (VOCs)• NOx = NO + NO2

Human activityFires Biosphere

emissions

Many processes affected by climate

NOxNOx

NOxVOCs

NOx

NOxVOCs

VOCsVOCs

VOCsCO

CO CH4

CH4

Soup of chemical reactionsOzone is produced in the atmosphere in sunlight.

Observations imply importance of biogenic emissions to atmospheric chemistry

Probability of ozone exceedance

Northeast/ mid Atlantic in summer

maximum daily temperature (K)

Pro

babi

lity

Reasons for increasing probability of ozone exceedances at higher max Temps:• Greater stagnation + clear skies• Faster chemical reactions.• Greater biogenic emissions, e.g. isoprene

Lin et al., 2000

1988, hottest on record

Day

sNumber of summer days with ozone exceedances, mean over sites in Northeast

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Life cycle of particulate matter (PM, aerosols)

nucleation coagulation

condensation

wildfirescombustion

soil dustsea salt

. . ... .

cycling

ultra-fine(<0.01 mm)

fine(0.01-1 mm)

cloud(1-100 mm)

combustionvolcanoes

agriculturebiosphere

coarse(1-10 mm) scavenging

precursor gases

Climate change affects many processes, including gas-particle partitioning.

Soup of chemical reactions

NOxNOx

NOx

NOxNOx

VOCs

VOCsVOCs

VOCsVOCs

SO2

NH3

SO2

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Models are useful tools to interpret observations and to investigate past or future atmospheres.

emissionstransportdilutionchemistry

particulate matter (PM)and ozone pollution

population

GEOS-Chem chemical transport model: Global 3-D model describes the transport and chemical evolution of atmospheric pollutants

winds Winds carry pollutants to other boxes.Emissions + chemistry

calculated within box

Meteorology driving GEOS-Chem can come from observations or climate models.

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Meteorology driving 3-D chemical models comes from climate models:

Two ways to run climate models• “nudged” with observations• calculated from first principles

All climate models depend on basic physics to describe motions and thermodynamics of the atmosphere:

E.g., vertical structure is described by hydrostatic equation

( ) ( ) a adPP z P z dz gdz gdz

Climate models also depend on parameterizations for many processes.E.g., microphysics of cloud droplet formation.

Physics + Parameterized processes

Tilt of earth, geography, greenhouse gas content

Weather + Climate

Input Climate model Output

Validation of models involves scrupulously comparing model results to observations.

Since, 1800s, input of reactive nitrogen to ecosystems has increased by more than a factor of 3 globally due to human activity.r = Correlation coefficients NMB = normalized mean biases MNB= mean normalized biases

observations model

Zhang et al., 2011Nitrate wet deposition fluxes, 2006

Biogenic volatile organic compounds (BVOCs): Emissions Parameterization in GEOS-Chem

Base emission for a specified mix of different plant functional types at specified meteorological conditions

INPUTS

MODELBase emissions are scaled for local conditions: vegetation

type, leaf area index, temperature, solar insolation

OUTPUTGridded BVOC emissions

[atoms C cm-2 s-1](includes isoprene and monoterpenes)

Guenther et al., 2006

Big isoprene emitters: Oaks, spruce, firs, sweetgum

Other parameterizations in GEOS-Chem

Soil NOx emissions = f(vegetation type, temperature, precipitation history, canopy reduction, fertilizer usage)

Dry deposition = Resistance in series scheme, with these resistances:Aerodynamic resistance to surfaceBoundary resistance at surface of leafCanopy surface resistance = f(Leaf area index, direct and diffuse sunlight,

gas or particle type)

Wet deposition = f(clouds, rainfall, gas or particle type)

Difficulty is scaling up from small-scale processes to global scale.

How will changing climate affect changing organic carbon particles in the atmosphere?

Fine mass of organic particles, annual mean.

Southeast is a big contributor due to dense vegetation.

Organic particles contribute about 20-40% of particle mass in the US.

What will change in future atmosphere:

air temperature

biogenic emissions

land usevegetationMalm et al., 2004

Effects of Future Biosphere Changes on Air Quality

Plants

Biogenic volatile organic

compound (VOC)

Secondary organic aerosol

(SOA)

[Heald et al. 2008]

Simulated 2000-2100 changes in annual surface SOA concentrations

climate change only climate-driven biogenic emissions change only

anthropogenic land use change only

+ +

Effects of Future Biosphere Changes on Air Quality

[Wu et al. 2011]

Climate- and CO2-driven 2000-2100 changes in areal fractional coverage

Temperate broad-leaved trees Boreal needle-leaved trees

Associated changes in SOA concentrations

20% increase in SOA global burden

Effects of Future Biosphere Changes on Air Quality

Simulated 2000-2150 changes in surface ozone concentrations

Ozone deposition could have consequences for carbon uptake in plants.

climate- and CO2-driven vegetation change only

Plants

Leaf surface Ozone loss

Biogenic VOC

[Wu et al. 2011]

+

++ -

-

Ozone increase or loss (depends

on NOx)

ppb

[Wu et al. 2011]

2000-2100 changes gross primary productivity due to ozone changes

Increasing ozone due to climate change can decrease gross primary productivity.

Sitch et al., 2007

2000 ozone

2100 ozone

GPP GPP

Observed Area burned

Observed Meteorology

Regression Model

Relationship between area burned + meteorology

observationsmodel

How will changing climate affect wildfires and air quality?

Yue et al., 2011

We build a fire prediction scheme that can capture interannual variability in area burned in the Western US.Area burned = f (temperature, rainfall, Palmer drought index, relative humidity, other indices. . .)Each ecosystem has its own relationship between area burned and meteorology.

Ensemble of climate models predict warmer and drier summers in the west.

Temperature Temperature

PrecipitationPrecipitation

Relative Humidity Relative Humidity

DJF JJA

2000-2050 change in meteorological fields, ensemble medians in each gridbox.

A1B scenario – moderate increases in greenhouse gases.

Yue et al., 2011

Meteorology from 15 climate

models

Regression Model

Calculated area burned for present-day

and future

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We calculate changes in area burned for 2000-2050, using an ensemble of IPCC model results.Area burned increases 20-120% across Western US, but models show range of uncertainty.

Spracklen et al., 2009Yue et al., 2011

2000-2050 changes in meteorology from 15 IPCC AR4 climate models.

different ecosystems in Western US

The total area burned is predicted to increase by 60~120% over western US by the midcentury

Years

1986 1990 1995 2000 2051 2055 2060 2065

Present-day observations

Ensemble median values of predictions

Spread of predictions

1990 2000 2055 2065

Change in area burned is especially large in Southwest US, where area burned doubles.

105 ha

105 haYue et al., 2011

The length of fire season increases by 3 weeks in 2050s relative to present day.

163 days 185 days

End day

Start day

Calculations with observations

Ensemble median values of predictions

Spread of predictions

Yue et al., 2011

Can we also simulate the effects of insect outbreaks on forests in a global chemistry model?

Arneth and Niinemets, 2010

Both fires and insect outbreaks are influenced by climate. Can we build a probabilistic model of insect outbreaks by ecosystem?

Investigations of the oxidation capacity of the atmosphere during the Last Glacial Maximum

Ongoing project to look at how changing land cover and climate affect oxidation capacity of atmosphere.Biogenic species could play a role: decreased concentrations could increase OH levels.

Murray et al., in progress

Emissions of biogenic species

Annual mean emissions of isoprene

Present-day

Preindustrial

CLIMAP LGM

Webb LGM

Comparison to observed sulfate concentrations shows good agreement.

Sequence shows increasing sulfate from 1950-1980, followed by a decline in recent years. Most of aerosol has already cleared by 2010.

1950 1960

1970 1980

1990 2001

Leibensperger et al., 2011

Calculated trend in surface sulfate concentrations, 1950- 2001.

Trend in aerosols over United States suggests cleaner skies, possible warming.

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Each scenario includes an ensemble of 3 simulations.

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GISS GCM A1B greenhouse gases constant aerosols

A1B greenhouse gases zero US aerosols

1950 1975 2000 2025 2050

We test the effect of changing U.S. aerosols on regional climate.

Mickley et al., 2011

Two scenarios.

Removal of anthropogenic aerosols over US increases annual mean surface temperatures by 0.5 o C. Summertime temperatures increase as much as 2 oC during heatwaves.

Mean 2010-2050 temperature difference: No-US-aerosol case – ControlWhite areas signify no significant difference.Results from an ensemble of 3 for each case.

Warming due to 2010-2050 trend in greenhouse gases.

Additional warming due to zeroing of US aerosols

Mickley et al., 201127

Calculation of maximum temperatures in climate models is sensitive to choice of parameters having to do with land cover/soil.

Lower and upper estimates of JJA maximum temperatures in 2x CO2 atmosphere

Central 80% range of increases for 44 versions of one climate model

oC

Percent variability in Tmax accounted for by vegetation parameters.

Clark et al., 2010 28

Forest roughness parameter Vegetation root depth

Lower estimate Upper estimate

50%30%6%

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Effect of kudzu invasion on surface air quality

Hickman et al., 2010

By fixing atmospheric nitrogen at a rapid rate, kudzu invasion leads to significant release of nitric oxide, an ozone precursor.

Mean July emissions at 3 sites in Georgia

kudzu native

NO

N2O

Calculated change in the number of ozone exceedance days in summer due to a 28% increase in soil NOx emissions accompanying large kudzu invasion.

days

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Collaborations with ecologists:• Enhance knowledge of interactions between biosphere and atmosphere, and

how to model those interactions• Improve understanding of response of ecosystems to climate change

Specific processes that will change with changing climate or changing emissionsbiogenic emissions, including methane, VOCsdeposition of nitrogen, ozone, and other speciessoil NOx emissionsinsect-driven outbreaks and their consequences