The impact of shattering on derived microphysical parameters from optical array probes: results from ISDAC and IDEAS-2011

Prior estimates of ice crystal size distributions (SDs) derived from optical array probes have been artificially amplified by small ice crystals generated from the shattering of large ice crystals on probe tips. To assess the extent to which data acquired before the development of redesigned tips and processing algorithms can be used, the degree to which various bulk cloud parameters are affected by shattering is determined here. Here, data acquired by two adjacent two-dimensional cloud probes (2DCs) with standard and anti-shatter tips and processed with and without anti-shattering algorithms during the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) and the 2011 Instrumentation Development and Education in Airborne Science (IDEAS-2011) campaign are used to derive total concentration, extinction, ice water content, reflectivity, effective diameter, median mass diameter, mass-weighted terminal velocity and single-scattering properties. Parameters based on higher moments of SDs could be estimated from standard probes within uncertainties required for model and remote sensing studies; but, parameters based on lower moments of SDs, such as total concentration, varied by factors of up to 5, especially for maximum dimensions less than 500 μm. This is much larger than the reduction of ice water content and bulk extinction by about 20% for the modified tips, and changes in effective radius, mass weighted terminal velocity, and median mass diameter by less than 15%. The modified tips changed the asymmetry parameter and single scatter albedo by up to 0.01, less than the certainty with which they need to be known for climate studies. Comparisons of our findings against those of previous studies are made.