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  • American Meteorological Society  (2)
  • 2010-2014  (2)
  • 2014  (2)
  • 1
    Publication Date: 2014-12-01
    Description: Prior estimates of ice crystal size distributions derived from 2D cloud probes (2DCs) have been artificially amplified by small ice crystals generated from the shattering of large ice crystals on the probe tips. Although antishatter tips and algorithms exist, there is considerable uncertainty in their effectiveness. This paper examines differences in ice crystal size distributions from adjacent 2DCs with standard and antishatter tips, and processed with and without antishattering algorithms. The measurements were obtained from the National Research Council of Canada Convair-580 during the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) and the National Center for Atmospheric Research C-130 during the 2011 Instrumentation Development and Education in Airborne Science (IDEAS-2011). The 2DC size distributions are compared with those from the Holographic Detector for Clouds (HOLODEC), which has antishatter tips and allows for identification of shattering through spatial statistics. The ratio of the number concentration N of particles with maximum dimensions 125–500 μm from the 2DC with standard tips to that from the 2DC with modified tips was correlated with median mass diameter and perimeter divided by area, but not with airspeed, attack, and attitude angles. Antishatter tips and algorithms reduced N by up to a factor of 10 for IDEAS-2011 and ISDAC, but neither alone removed all artifacts. For the period with coincident data, both N from the HOLODEC and 2DC with modified tips are around 5 × 10−3 L−1 μm−1, suggesting that antishatter tips and algorithms combined remove artifacts from the 2DC for the conditions sampled during IDEAS-2011.
    Print ISSN: 0739-0572
    Electronic ISSN: 1520-0426
    Topics: Geography , Geosciences , Physics
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  • 2
    Publication Date: 2014-10-01
    Description: A recent study showed that the ratio of the number of distribution functions derived from 2D cloud probes (2DCs) with standard tips to those with antishatter tips used during the 2008 Indirect and Semidirect Aerosol Campaign (ISDAC) and Instrumentation Development and Education in Airborne Science 2011 (IDEAS-2011) was greater than 1 for ice crystals with maximum dimension D 〈 500 μm. To assess the applicability of 2DC data obtained without antishatter tips previously used in parameterization schemes for numerical models and remote sensing retrievals, the impacts of artifacts on bulk microphysical and scattering properties were examined by quantifying differences between such properties derived from 2DCs with standard and antishatter tips, and with and without the use of shatter detection algorithms using the ISDAC and IDEAS-2011 data. Using either modified tips or algorithms changed the quantities dominated by higher-order moments, such as ice water content, bulk extinction, effective radius, mass-weighted terminal velocity, median mass diameter, asymmetry parameter, and single-scatter albedo, at wavenumbers from 5 to 100 cm−1 and wavelengths of 0.5–5 μm by less than 20%. This is significantly less than the fractional changes quantities dominated by lower-order moments, such as number concentration. The results suggest that model parameterizations and remote sensing techniques based on higher-order moments of ice particle size distributions obtained in conditions similar to those sampled during IDEAS-2011 and ISDAC derived from 2DCs are not substantially biased by shattered remnants.
    Print ISSN: 0739-0572
    Electronic ISSN: 1520-0426
    Topics: Geography , Geosciences , Physics
    Location Call Number Expected Availability
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