CIRPAS Twin Otter Aircraft
Last updated 20 October 2000

Proposed aircraft schedule:
Five week deployment in Asia from late March to the end of April 2001.

Contact person:
John Seinfeld, California Institute of Technology
Phone: 626-395-4100
Fax: 626-585-1729

Description of platform objectives:

A major goal of the ACE-Asia intensive experiment is to survey the air leaving Eastern Asia to characterize aerosol physical, chemical, and optical properties and their variation with time and space, emphasizing variations with altitude and distance from the continent. We are proposing to carry out a suite of airborne measurements aboard the CIRPAS Twin Otter aircraft. Aerosol size distributions will be measured on the Twin Otter with an array of four instrµments, spanning the diameter range of 30 nm to 30 µm, consisting of three optical particle counters (PCASP, FSSP, CAPS) and one differential mobility analyzer (DMA). Aerosol chemical composition will be measured with 5-stage MOUDI cascade impactors and an aerosol mass spectrometer. Aerosol optical properties will be obtained by four nephelometers and a Particle Soot Absorption Photometer. This combination of instrµments will yield light scattering, absorption, 180° backscatter, extinction, and lidar ratio, single scatter albedo, and Angstrom exponent. Hygroscopic properties will be available from the low and high RH nephelometers and a tandem differential mobility analyzer (TDMA). The 14-wavelength NASA Ames airborne tracking sunphotometer will continuously measure the optical depth of the column of air between the aircraft and the top of the atmosphere, providing the essential data to evaluate the extent of column radiative closure achievable.

The following PIs have been funded to participate:
Organizations Participating
California Institute of Technology John Seinfeld, Rick Flagan, Jian Wang, Jose Jimenix, Roya Bahreini, Brian Mader
Naval Post Graduate School Haf Jonsson
Texas A&M University Don Collins
Nasa Ames Phil Russell, Maura Rabbette
University of Washington Dean Hegg
Measurement Instrument PI Others
Aerosol size distribution
10 nm-1µm
DMA System (cabin) Seinfeld/Flagan  Jian Wang 
Aerosol hygroscopic properties TDMA System (cabin) Don Collins  
Aerosol composition
40 nm-3 µm
volatile components
Aerosol Mass Spectrometer (cabin) Seinfeld/Flagan  Jose Jimenez
Roya Bahreini
Aerosol optical depth
14 channels
NASA Sunphotometer (cabin) P. Russell NASA team
EC/OC/Organic speciation Denuder/Filter Samplers (cabin) Seinfeld/Flagan  Brian Mader (CIT)
EC/OC/Organic speciation/Inorganic ions MSP MOUDI Impactor/Filter Sampler (wing) D. Hegg/H. Jonsson
Aerosol optical properties TSI Nephelometer
Soot Photometer (cabin)
H. Jonsson (NPS)
Aerosol hygroscopic properties Humidigraph (3 RR Nephelometers) (cabin) D. Hegg (UW)  
Aerosol size distribution
>0.3 µm (CAPS)
0.1-2.5 µm (PCASP)
>0.5 µm (FSSP)

CAPS Probe
FSSP (wing)
H. Jonsson (NPS)
Aerosol size distribution
>0.5 µm
TSI Aerodynamic Particle Sizer (cabin) H. Jonsson (NPS)
Total aerosol number concentration Condensation Nucleus Counters (CNCs) H. Jonsson (NPS)
          Downwelling and 
          Upwelling  Solar 
          Spectral Irradiance, 
          1320 channels
NASA Ames Solar Spectral Flux Radiometer (cabin) Maura Rabbette NASA Ames team