Transcript Accent Plus Symposium, Urbino, Italy, 17-20 Sep2013

Observations of Enhanced Black Carbon
radiative forcing over an Urban
Environment
A.S.Panicker, G. Pandithurai, P.D.Safai, S.Dipu
Indian Institute of Tropical Meteorology
Pashan, Pune-411008, India
Email : [email protected]
Accent Plus Symposium, Urbino, Italy, 17-20 Sep2013
Objectives

To estimate Composite (total) aerosol direct
radiative forcing in short wavelength region using
chemical composition data

To Estimate direct radiative forcing solely due to
Black Carbon (BC)

To find the contribution of BC to total aerosol
radiative forcing
Accent Plus Symposium, Urbino, Italy, 17-20 Sep2013
Experimental site
Observations and Models Used for
study…
Instruments
► Aethalometer
► High
volume sampler
► Sun/Sky radiometer
Models
►
►
OPTICAL PROPERTIES OF AEROSOLS AND CLOUDS
(OPAC)
SANTA BARBARA DISCRETE ORDINATE RADIATIVE
TRANSFER MODEL (SBDART)
Aethalometer, High Volume sampler, Sun/Skyradimeter
Aethalometer
High volume sampler
Prede Sun/Skyradiometer
MODELS
OPAC (Optical Properties of Aerosols and Clouds)
►
OPAC Estimates Optical properties of aerosols from 0.240µm (AOD,SSA,ASP, Extinction coeff etc.).
►
Uses atmospheric chemistry data sets as Input
►
Data sets from High volume sampler ( water soluble and acid
soluble components) and Aethalometer (Black carbon)
SBDART
(SANTA BARBARA DISCRETE ORDINATE
RADIATIVE TRANSFER MODEL)
►
1-dimensional model – Incorporates aerosol observations
►
Plane parallel atmosphere
►
Line-by-Line integration
►
Default Temperature & water vapor profiles: TROPICAL, MIDLATITUDE SUMMER , MID-LATITUDE WINTER , SUB-ARCTIC
SUMMER , SUB-ARCTIC WINTER .
SBDART.....
Aerosol Optical Depth

Aerosol Single Scattering Albedo

Asymmetry Parameter

Derived
from Observations
Surface Albedo
(From MODIS)

Water vapor column (From MODIS)

Column ozone(From TOMS/OMI)
Fluxes at different levels (Surface & TOA)

Downward, Upward, and Direct Fluxes
Forcing  F  F aerosol  F  F clean
Methodology
Aerosol Radiative forcing = Fluxes with aerosols- Fluxes with out aerosols
 Aerosol Short wave radiative forcing
estimation for composite aerosols
 Water soluble, Acid soluble componets and
BC data as inputs in OPAC
 Aerosol Short wave radiative forcing
estimation for Black Carbon (BC)
aerosols
 Black carbon data alone as input in
OPAC
 OPAC derived Composite aerosol optical
properties: AOD, SSA and ASP from 0.2-4
μm as inputs in SBDART
 OPAC derived BC aerosol AOD, SSA
and ASP from 0.2-4 μm as inputs in
SBDART
 Short wave radiative forcing at Surface,
TOA and Atmosphere by total aerosol mass
 Short wave radiative forcing at
Surface, TOA and Atmosphere byBC
aerosols
Comparison of aerosol properties by OPAC and Sky
radiometer
0.85
0.80
0.75
AOD,SSA (500nm)
0.70
0.65
OPAC AOD
Observed AOD
OPAC SSA
Observed SSA
0.60
0.55
0.50
0.45
0.40
0.35
0.30
Oct04
Nov04
Jan05
Feb05
Month
Mar05
Apr05
WS/WIS and BC mass
Months
Mass fraction (μg/m3)
Water-Insoluble
Water Soluble
BC
% BC mass
to TSP
October -04
140
31.3
3.91
2.23
November-04
139.8
44.9
5.76
3.02
January-05
85.3
56.9
6.79
4.56
February-05
114.1
53.8
5.87
3.4
March-05
184.2
46.8
4.10
1.7
April-05
188.9
55.3
3.90
1.6
SW radiative forcing by Composite and BC aerosols at surface and
TOA
Month
Oct04
Nov04
Jan05
Feb05
March05
Apr05
5
0
-5
-10
-15
-20
-2
Surface Forcing(Wm )
-2
TOA forcing(Wm )
-2
Composite forcing (Wm )
-2
BC forcing(Wm )
a
b
10
0
-10
-20
-30
-40
-50
Oct04
Nov04
Jan05
Feb05
March05
Apr05
Seasonal averages of shortwave atmospheric forcing for
composite and for BC aerosols over Pune
CARF@Pune
BCAF@Pune
-2
Atmospheric forcing (Wm )
50
40
30
20
10
0
Post-monsoon
winter
Season
pre-monsoon
Summary
•
OPAC derived aerosol optical properties for composite aerosols and for BC
fraction alone has been incorporated in SBDART to derive composite and BC
only aerosol forcing respectively for different seasons
•
The atmospheric forcing derived for composite aerosols were found to be
+35.5, +32.9, +47.6 Wm-2 and for BC fraction alone these were found to be
+18.8, + 23.4 and +17.2 Wm-2 during post-monsoon, winter and pre-monsoon,
respectively.
•
The study suggests that eventhogh BC contributes 1.6-5% by mass in total
aerosols loading, on an average, it contributes to around 55% of the total
atmospheric aerosol radiative forcing due to strong radiative absorption by
BC.
Acknowledgements


Prof. Michele Maione, ACCENT plus, W.M.O for
supports
Director IITM