# Presentation: 400221

## 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

## Co-authors

- 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*

## AATS-6

**AATS-6**

**AATS-14**

**NASA Ames Airborne Sunphotometers (AATS)                 AOD and H****2****O**

**C-130**

**Twin Otter**

**(350-1558 nm)**

**(380-1020 nm)**

**Notes:**
AATS-6 was flown on the C-130 and AATS-14 on the Twin Otter

## AATS vertical profiles during ACE-Asia

- AATS-14
- AATS-6

**Notes:**
Shows location of all 26 AATS-14 and 26 AATS-6 vertical profiles

## Slide 5

**Notes:**
Vertical profile from AATS-14. 13 wavelengths from 353 to 1558 nm. Spectrum is monotonic (wavelength in order). Left is AOD which should decrease monotonically as you climb. Dashed lines are smoothed spline fits. A differentiation of these yields spectral extinction (right panel). Two aerosol layers and a clean layer are visible. Notice wavelength dependence. Large particles in the upper layer (dust) and low (sea salt) smaller particles elsewhere (pollution).

## Slide 6

## Slide 7

## Slide 8

## 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=8m)*
- 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=8m)*
- correct to ambient RH

- +

- *correction not required or done

**Notes:**
How to get extinction from in-situ measurements. No need to explain corrections.

## 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)

**Notes:**
Another way to get extinction from in-situ 

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

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

**Wang et al. [2002]**

## Slide 12

## Slide 13

## Slide 14

## Slide 15

## Slide 16

## Slide 17

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

## Slide 19

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

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

**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)