Long term trends in aerosol optical characteristics observed in Ispra
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Long term trends in aerosol optical characteristics observed in Ispra * (*) unpublished results: please do not spread JP Putaud and ABC-IS people M Adam, C Belis, F Cavalli, A Dell’Acqua, K Douglas, C Gruening, S Martins Dos Santos, R Passarella, V Pedroni

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Long term trends in aerosol optical characteristics observed in Ispra*

(*) unpublished results: please do not spread

JP Putaud and ABC-IS people

M Adam, C Belis, F Cavalli, A Dell’Acqua, K Douglas,

C Gruening, S Martins Dos Santos, R Passarella, V Pedroni

European Commission – Joint Research Centre – Air and Climate Unit

&

G Zibordi and his team

Water Resources Unit


  • Outline: in Ispra

  • Context

  • Objective

  • Results

  • Conclusions

  • Perspectives


EC in Ispra

  • Context

The role of short-lived atmospheric constituents in climate change has recently been further emphasized by the Clean Air and Climate Coalition

Current other counties:

Australia

Benin

Central African Republic

Chile

Colombia

Cote d’Ivoire

Denmark

Dominican Republic

Ethiopia

Finland

France

Germany

Ireland

Israel

Italy

Japan

Jordan

Maldives

Netherlands

New Zealand

Nigeria

Norway

Peru

Poland

South Korea

United Kingdom

Feb. 2012:

United States

Bangladesh

Canada

Ghana

Mexico

Sweden

1


The role of short-lived atmospheric constituents in climate change has recently been further emphasized by the Clean Air and Climate Coalition : www.unep.org/ccac/

“Pollutants that are short-lived in the atmosphere, such as black carbon (soot), methane, tropospheric ozone and some hydrofluorocarbons (HFCs), can have harmful impacts on human health, agriculture and ecosystems.

These short-lived climate pollutants – or SLCPs – are also responsible for a substantial fraction of current global warming, as well as having regional climate impact”.

2


O in Ispra3

+0.5 Wm-2

  • Context

IPCC AR5

BC

+0.6 Wm-2

3


Ensemble mean surface ozone in 2000 (Dentener et al., 2006)* in Ispra

  • Context

  • Radiative forcing by SLCPs is highly uncertain because of:

  • Very diverse (primary and secondary) sources

  • Short atmospheric lifetime

(*) circles (upper part) indicate regional averaged measurements

4

1

1

1


  • Context in Ispra

  • Radiative forcing by SLCPs is highly uncertain because of:

  • Very diverse (primary and secondary) sources

  • Short atmospheric lifetime

Annual mean surface layer modelled BC (Vignati et al., 2010)

5


well internally mixed BC in Ispra

BC as a coated core

externally mixed BC

+ 0.54 W m-2

+ 0.27 W m-2

+ 0.78 W m-2

  • Context

  • Radiative forcing by SLCPs is highly uncertain because of:

  • Very diverse (primary and secondary) sources

  • Short atmospheric lifetime

  • Complex interaction with light (aerosol)

M. Z. Jacobson, 2001

6


  • Context in Ispra

  • Radiative forcing by SLCPs is highly uncertain because of:

  • Very diverse (primary and secondary) sources

  • Short atmospheric lifetime

  • Complex interaction with light (aerosol)

  • day time fraction solar constantatmosphere transmittancecloud fractionsurface albedo

  • aerosol single scattering albedoupper scatter fractionaerosol optical depth

  • There are very few accurate measurements of the aerosol optical property across the world

Fa = -bFT T² (1-AC) [ωaa(1-RS)² - 2(1-ωa)RS] δa

7

1

1


2. Objective in Ispra

Detect changes in aerosol optical properties resulting from European policies from measurements (JRC Ispra)

2000

2005

2010

1985

1990

1995

Precipitation chemistry

Gas phase pollutants (SO2, NOx, O3, CO,…)

PM mass and inorganic constituents (SO4, NO3, NH4, …)

OC + EC

Aerosol scattering and absorption coefficients & number size distribution

Aerosol vertical profile

Aerosol hygroscopicity

8


3. Methods in Ispra

Measuring relevant variables with the suitable accuracy and precision

Scattering () and backscattering (b)Nephelometer(1)

Absorption ()Aethalometer(1)

Aerosol optical depth (δa)Sunphotometer(2)

Instruments are regularly calibrated at the WCCAP (1)

or by AERONET (2)

a = 0.08 + 1.85b– 2.97b²

ωa = /(+)

Fa = -bFT T² (1-AC) [ωaa(1-RS)² - 2(1-ωa)RS] δa

9


Measured in Ispra

scatt. and abs. coefficients

Measured NSD

Calculated

scat. and abs. coefficients

Mie equations

Retrieved minst

3. Methods

Scattering (and absorption) coefficients corrected for RH effects

10


Mean GF in Ispra90 (165 nm)

GFRH (165 nm)

GF(RH) = (1-RH)-γ

Mie equations

3. Methods

Scattering (and absorption) coefficients corrected for RH effects

Corrected

scatt. and abs. coefficients

(dry)

x(RH)

water volume fraction

Retrieved minst

NSD(RH)

minst = x mH2O + (1-x) mdry

  • Corrections from intrument RH to 0%:

    • 17 ± 15 % for scattering, 2 ± 1 % for absorption, 2 ± 2 % for single scatering albedo

11

1

1

1


3. Methods in Ispra

Monthly data series are fitted (least squares) with the formula:

time (month)

constant

slope

seasonal cycle + higher frequency

residual

monthly mean for ~ normally distributed variables

or

ln(monthly mean) for ~ log-normally distributed variables

e.g. Collaud-Cohen et al., 2013

12


4. Results in Ispra

Aerosol optical depth (sunphotometer)

13

1

1

1

1

1


4. Results in Ispra

Aerosol optical depth (sunphotometer)

-4.5 ± 2.1 % yr-1

-3.1 ± 0.9 % yr-1

14


4. Results in Ispra

Light scattering and absorption by aerosols (in situ)

15


4. Results in Ispra

Light scattering and absorption by aerosols (in situ)

-2.8 ± 0.5 % yr-1

16


4. Results in Ispra

Light scattering and absorption by aerosols (in situ)

-1.2 ± 0.3 % yr-1

17


4. Results in Ispra

Aerosol single scattering albedo (in situ):

ωa = /(+)

-0.6 ± 0.2 % yr-1

18


4. Results in Ispra

Aerosol single scattering albedo (sunphotometer)

-0.6 ± 0.1 % yr-1

-0.7 ± 0.2 % yr-1

19

1

1

1

1


4. Results in Ispra

Aerosol backscatter ratio (in situ)

-0.1 ± 0.3 % yr-1

20


Mean GF in Ispra90 (165 nm)

GFRH (165 nm)

GF(RH) = (1-RH)-γ

Corrected

scat. and abs. coefficients

(ambient)

x(RH)

water volume fraction

Retrieved minst

NSD(RH)

Mie equations

minst = x mH2O + (1-x) mdry

3. (Methods)

Conversion of measurements (0% RH) to ambient conditions

4. Results

Fa = -bFT T² (1-AC) [ωaa(1-RS)² - 2(1-ωa)RS] δa

Fa = -bFT T² (1-AC) [ωaa(1-RS)² - 2(1-ωa)RS] δa

21


4. Results (cont’d) in Ispra

Direct radiative forcing by aerosols

average = -10 ± 4 W m-2 (1)

22


4. Results in Ispra

Direct radiative forcing by aerosols

all: -(-0.9 ± 0.2) W m-2 yr-1

1

23


4. Results in Ispra

Direct radiative forcing by aerosols

all: -(-0.9 ± 0.2) W m-2 yr-1

AOT: -(-0.8 ± 0.2) W m-2 yr-1

24

1


4. Results in Ispra

Direct radiative forcing by aerosols

all: -(-0.9 ± 0.2) W m-2 yr-1

AOT: -(-0.8 ± 0.2) W m-2 yr-1

SSA: -(-0.3 ± 0.1) W m-2 yr-1

25

1

1

1

1


4. Results in Ispra

Direct radiative forcing by aerosols

all: -(-0.9 ± 0.2) W m-2 yr-1

AOT: -(-0.8 ± 0.2) W m-2 yr-1

SSA: -(-0.3 ± 0.1) W m-2 yr-1

26


  • 4. Conclusions in Ispra

  • Long term observation of atmospheric variables may help assess the impact of AQ and CC policies, and develop smarter policies

  • Our data set suggests that the potential mitigation of global warming via the abatement of soot emissions is marginal

  • As the spatial representativeness of any measurement is limited, networks are essential

27


  • 5. Perspectives in Ispra

  • The formula does not account for the vertical distribution of aerosols

  •  use of LiDAR and radiative transfer model

  • Also for investigating the radiative forcing by aerosols above clouds (also important for cloud formation and water cycle)

  • Make further use of networking to write more phenomenologies

  • The radiative forcing due to cloud adjustments to aerosols

Fa = -bFT T² (1-AC) [ωaa(1-RS)² - 2(1-ωa)RS] δa

28


  • 4. Perspectives in Ispra

  • The formula does not account for the vertical distribution of aerosols

  •  use of LiDAR and radiative transfer model

  • Also for investigating the radiative forcing by aerosols above clouds

  • Make further use of networking to write more phenomenologies

  • The radiative forcing due to cloud adjustments to aerosols

  • Emerging HFCs with huge global warming potential

Fa = -bFT T² (1-AC) [ωaa(1-RS)² - 2(1-ωa)RS] δa

29


THANKS in Ispra

follow ABC-IS activities

athttp://abc-is.jrc.ec.europa.eu/



4. Results (cont’d) in Ispra

Elemental carbon and Equivalent Black Carbon

30


4. Results (cont’d) in Ispra

“EC” absorption cross section

31


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