Clear-column closure studies of lower tropospheric aerosol extinction during ACE-Asia using airborne sunphotometer, airborne in-situ

and ship-based lidar measurements

Beat Schmid et al. NASA Ames/BAER Institute, Sonoma, CA

Hegg, D, Covert, D, Univ. of Washington, Atmospheric Sciences, WA

Redemann, J, Bay Area Environmental Research, Institute, Sonoma, CA

Livingston, J , SRI, International, Menlo Park, CA

Russell P, NASA, Ames Research Institute, Moffett Field, CA

Wang, J, Flagan, R, Seinfeld, J, California Institute of Technology, Pasadena, CA

Bates, D, University of, Miami, Coral Gables, FL

Jonsson, H, CIRPAS, Marina, CA

Welton, E, GEST/UMBC, NASA Goddard Space Flight Center, Greenbelt, MD

Co-authors

AATS-6 AATS-14

NASA Ames Airborne Sunphotometers (AATS) AOD and H2O

C-130

Twin Otter

(350-1558 nm)(380-1020 nm)

AATS vertical profiles during ACE-Asia

AATS-14

AATS-6

20 lnln*ln aa

20 lnln*ln aa

In situ measurement of

Extinction =

Absorption

• Particle Soot Absorption Photometer (PSAP, =550nm)

• noisy (averaging)• low RH

• Corrections (Bond et al., 1999)

– scattering contribution– …– inlet-cutoff (Da=8m)*– correct to ambient RH*

Scattering

• Nephelometers– TSI: = 450, 550, 700 nm,

low RH

– RR: = 550 nm, RH=20,60,85%

• Corrections (Anderson&Ogren, 1998)

– light source

– angular truncation (7°-170°)

– inlet-cutoff (Da=8m)*

– correct to ambient RH

+

*correction not required or done

Extinction the “hard way”: Compute from in situ measurement of size

distribution and composition

• Twin DMA, D = 15 - 1000 nm (close to ambient RH)• Aerodynamic Particle Sizer, D = 0.5 - 8 m (drier than ambient RH),

• adjust to ambient RH• compute extinction, needs m } needs composition

Wang et al. 2002, JGR (in press)

Chemical Composition and size distributions, flight 11, April 17, 2001

Wang et al. [2002]

Extinction closure between AATS-14 and Neph+PSAP for 14 profiles

H2O closure between AATS-14 and in-situ for 26 profiles

How well did past campaigns do on AATS vs Neph+PSAP comparisons?

U.S. East Coast, 1996 (Hegg et al., 1997, Hartley et al., 2000)

Canary Islands, 1997 (Schmid et al., 2000)

Eastern Asia, 2001

C-130: Redemann et al., 2003

Twin Otter: Schmid et al., 2003

Southern Africa (Magi et al., 2002)

U.S. East Coast, 2001 Hobbs et al., (in preparation)