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 0.2 40 µm (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

,

MID LATITUDE 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



OPAC derived Composite aerosol optical properties: 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

 

Aerosol Short wave radiative forcing estimation for Black Carbon (BC) aerosols Black carbon data alone as input in OPAC



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 byBC aerosols

Comparison of aerosol properties by OPAC and Sky radiometer 0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

0.45

0.40

0.35

0.30

OPAC AOD Observed AOD OPAC SSA Observed SSA Oct04 Nov04 Jan05 Feb05

Month

Mar05 Apr05

Months

WS/WIS and BC mass

Mass fraction ( μg/m3) Water-Insoluble Water Soluble BC % BC mass to TSP October -04 November-04 January-05 February-05 March-05 April-05 140 139.8

85.3 114.1 184.2 188.9

31.3

44.9

56.9 53.8 46.8 55.3 3.91 5.76 6.79

5.87

4.10

3.90

2.23

3.02

4.56

3.4

1.7

1.6

SW radiative forcing by Composite and BC aerosols at surface and TOA 10 0 -10 -20 -30 -40 -50 5 0 -5 -10 -15 -20

a

Oct04 Nov04

b

Oct04 Month Jan05 Feb05 March05 Apr05 Nov04 Surface Forcing(Wm -2 ) TOA forcing(Wm -2 ) Jan05 Feb05 March05 Apr05

Seasonal averages of shortwave atmospheric forcing for composite and for BC aerosols over Pune 50 40 30 CARF@Pune BCAF@Pune 20 10 0 Post-monsoon winter 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