The microphysical properties of arctic cirrus derived from in-situ measurements during ISDAC and M-PACE: implications for the importance of small ice crystals
Abstract
In-situ observations on the size and shape of particles in arctic cirrus are less common than those in mid-latitudes and the Tropics, but are required to determine cirrus sedimentation and single-scattering properties, factors that impact cirrus radiative forcing. In this study, data collected on two flights of the University of North Dakota Citation during the Mixed-Phase Arctic Cloud Experiment (M-PACE) and on 5 flights of the National Research Council of Canada Convair-580 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) are used to determine how cirrus size distributions, total crystal concentrations, effective radii, bulk mass and extinction vary with temperature and altitude. Past studies have shown that small ice crystals (those with maximum dimensions D less than 50 micrometers) make uncertain and possibly highly variable contributions to these properties. Thus, in-situ measurements of small ice crystals from a Cloud and Aerosol Spectrometer (CAS), a Cloud Droplet Probe (CDP), a Forward Scattering Spectrometer Probe (FSSP), a Cloud Particle Imager (CPI) and a two-dimensional stereo probe (2DS) are compared as functions of temperature, aircraft true air speed, angle of attack, and large ice crystal concentrations (particles with D > 100 micrometers) to assess the degree to which the shattering of large ice crystals on protruding components of different probes artificially amplifies small ice crystal concentrations. Thereafter, the arctic cirrus properties and crystal shapes are compared against values observed in mid-latitude and tropical cirrus. Implications for the evaluation of models and remote sensing retrievals, for the development of cloud parameterizations, and the impact of clouds on radiation are discussed.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.A43A0168M
- Keywords:
-
- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE / Aerosols and particles;
- 0321 ATMOSPHERIC COMPOSITION AND STRUCTURE / Cloud/radiation interaction;
- 0320 ATMOSPHERIC COMPOSITION AND STRUCTURE / Cloud physics and chemistry;
- 0360 ATMOSPHERIC COMPOSITION AND STRUCTURE / Radiation: transmission and scattering