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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, D04201, doi:10.1029/2003JD004032, 2004

Single particle measurements of the chemical composition of cirrus ice residue during CRYSTAL-FACE

D. J. Cziczo

Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA


D. M. Murphy

Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA


P. K. Hudson

Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA


D. S. Thomson

Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA


Abstract

The first real-time, in situ, investigation of the chemical composition of the residue of cirrus ice crystals was performed during July 2002. This study was undertaken on a NASA WB-57F high-altitude research aircraft as part of CRYSTAL-FACE, a field campaign which sought to further our understanding of the relation of clouds, water vapor, and climate by characterizing, among other parameters, anvil cirrus formed about the Florida peninsula. A counter flow virtual impactor (CVI) was used to separate cirrus ice from the unactivated interstitial aerosol particles and evaporate condensed-phase water. Residual material, on a crystal-by-crystal basis, was subsequently analyzed using the NOAA Aeronomy Laboratory's Particle Analysis by Laser Mass Spectrometry (PALMS) instrument. Sampling was performed from 5 to 15 km altitude and from 12° to 28° north latitude within cirrus originating over land and ocean. Chemical composition measurements provided several important results. Sea salt was often incorporated into cirrus, consistent with homogeneous ice formation by aerosol particles from the marine boundary layer. Size measurements showed that large particles preferentially froze over smaller ones. Meteoritic material was found within ice crystals, indicative of a relation between stratospheric aerosol particles and tropospheric clouds. Mineral dust was the dominant residue observed in clouds formed during a dust transport event from the Sahara, consistent with a heterogeneous freezing mechanism. These results show that chemical composition and size are important determinants of which aerosol particles form cirrus ice crystals.

Received 31 July 2003; accepted 24 December 2003; published 18 February 2004.

Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 1610 Global Change: Atmosphere (0315, 0325).

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Citation: Cziczo, D. J., D. M. Murphy, P. K. Hudson, and D. S. Thomson (2004), Single particle measurements of the chemical composition of cirrus ice residue during CRYSTAL-FACE, J. Geophys. Res., 109, D04201, doi:10.1029/2003JD004032.