The EvK2 Pyramid and the AERONET network

“Atmospheric Brown Cloud" Characterization via Sunphotometer Observations

G.P. Gobbi, F. Barnaba, and F. Angelini

CNR, Istituto di Scienze dell'Atmosfera e del Clima, Romacontact: g.gobbi@isac.cnr.it

Mountains, Witnesses of Global Changes: SHARE-Asia Project, Rome, November 16-17, 2005

Terra/MODIS, December 17, 2004:Thick haze and smoke along the Ganges Basin from  fires and large cities.  

EvK2

MODIS Dec-Feb 2001, 2002 and 2003 550nm Aerosol Optical Thickness

The Aerosol Optical Thickness at wavelength w (AOTw)quantifies the extinction introduced by atmospheric aerosols on

extraterrestrial solar radiation I0 before reaching the ground:

I=I0 exp-(AOTw)

Courtesy of Y. Kaufman et al.NASA GSFC

The Laboratory is located at 5050 m asl, 27º57’31’’ N – 86º48’48’’ E, at the foot of the Nepali side of Mt. Everest.

At the beginning of 2006, we plan to install at the EvK2 Pyramid a robotized Sunphotometer Cimel CE 318N

Ground-based measurements of AOT are more accurate than satellite ones, particularly at sites with high surface albedo;

Furthermore, sky-scanning sunphotometers can provide extended information on aerosol optical properties (Nakajima et al. [AO,1983, AO 1996]; Dubovik and King, [JGR, 2000] and Dubovik et al. [JGR, 2000])

SPECIFICATIONS:CE 318-N : sun-tracking and sky-scanning sunphotometerwith 5 filters centered at 440, 670, 870, 936,1020 nmBandwidth: 10 nm at full width half maximumOperating temperature: -30 to +60°C

Data transfer via GOES satellite link to NASA GSFC

The sunphotometer will operate in the framework of AERONET, the NASA AERosol RObotic NETwork

Further details:Optical head with 2 collimators 1.2° FOV:Sun tracking method by a 4-quadrant detector, Accuracy better than 0.1°Power requirements: 12 V – 10 Ah battery rechargeable by solar panelData Storage in EPROM readable on a PC

AERONET, the Aerosol Robotic Network (http://aeronet.gsfc.nasa.gov)

•The AERONET program is a federation of ground-based remote sensing aerosol stations. •The goal is to assess aerosol optical properties and validate satellite aerosol retrievals. •The network imposes standardization of instruments, calibration, and processing. •Data provides globally distributed observations of spectral aerosol optical depths, inversion products, and precipitable water in geographically diverse aerosol regimes. •Three levels of data are available from this website: Level 1.0 (unscreened), Level 1.5 (cloud-screened), and Level 2.0 (Cloud-screened and quality-assured).

AERONET, “quasi-real time” products available on the web site:

http://aeronet.gsfc.nasa.gov

-1

-0.5

0

0.5

1

Ång

strö

m d

iffer

ence

Beijing Jan-Aug 2005 - SVA

0.1 µm

0.15 µm

0.3 µm

0.2 µm

90%

70%

50%

30%

10%

-1

-0.5

0

0.5

1

0 0.5 1 1.5 2

Ång

strö

m d

iffer

ence

Kanpur Jan-Dec 2004

Ångström exponent

0.1 µm

0.15 µm

0.3 µm

0.2 µm

90%

70%

50%

30%

10%

0.3>AOT>0.150.4>AOT>0.30.7>AOT>0.41.0>AOT>0.7

1.5>AOT>1.02>AOT>1.53>AOT>2AOT>3

Rome Jan-Aug 2005

0.1 µm

0.15 µm

0.3 µm

0.2 µm

90%

70%

50%

30%

10%

0 0.5 1 1.5 2

Ispra 2004

Ångström exponent

0.1 µm

0.15 µm

0.3 µm

0.2 µm

90%

70%

50%

30%

10%

Further analysis will address the annual evolution of size-dependent aerosol properties from direct AOT measurements

(Kaufman, Gobbi & Koren, in preparation 2005)

The Indo-Gangean plan of AERONETCourtesy of B. Holben

Conclusions:

In the framework of the SHARE – ASIA project these observations are therefore expected to contribute answering the following questions:

• Which is the climatology of aerosol physical, chemical, and optical properties at this remote, high altitude station?

• How do aerosols radiative properties change as a consequence of transport of ABC or other type of air masses?

• What are the ABC effects on formation and lifetime of clouds?

• How good are satellite retrievals of aerosol AOT over this region?

Mountains, Witnesses of Global Changes: SHARE-Asia Project, Rome, November 16-17, 2005

THANK YOU VERY MUCH FOR YOU ATTENTION