Polarimetric Backscatter Sonde Observations of Southern Ocean Clouds and Aerosols

Balloon-borne polarimetric backscatter sonde (polarsonde) observations of aerosol and cloud during the approach of a cold front at Macquarie Island (54.499 S 158.937 E) are described. The polarsonde captures vertical profiles of cloud occurrence and phase. The cloud base and cloud top heights from the backscatter sonde compare favourably with observations made by a co-located cloud radar and ceilometer. An estimate of the total scatter probability from a liquid cloud layer at 1000 m height is used with a Monte Carlo model of the instrument to obtain cloud particle concentration, and this is compared to a measurement of cloud condensation nucleus concentration made at sea level. Backscatter from aerosol, as well as cloud, is significant. A high aerosol loading in part of the pre-frontal airmass is observed at altitudes up to 6 km. Below the melting level, the high cross-polarised return, relative to the co-polarised, indicates a substantial concentration of solid, non-spherical aerosol particles, which due to the high humidity cannot be sea salt or sulphate. A back trajectory analysis indicates that the observed aerosol includes continental dust.

Revisiting the differential freezing nucleus spectra derived from drop-freezing experiments: methods of calculation, applications, and confidence limits

The differential nucleus concentration defined in Vali (1971) is re-examined and methods are given for its application. The purpose of this document is to facilitate the use of differential spectra in describing the results of drop freezing, or similar, experiments and to thereby provide additional insights into the significance of the measurements. The additive nature of differential concentrations is used to show how the background contribution can be accounted for in the measurements. A method is presented to evaluate the confidence limits of the spectra derived from given sets of measurements.

Revisiting the differential freezing nucleus spectra derived from drop freezing experiments; methods of calculation, applications and confidence limits

The differential nucleus concentration defined in Vali (1971) is re-examined and methods are given for its calculation. The purpose of this document is to facilitate the use of the differential spectra in describing the results of drop freezing, or similar, experiments and thereby provide additional insights into the measurements. The additive nature of differential concentrations is used to show how the background contribution can be accounted for in the measurements. A method is presented to evaluate the confidence limits of the results at each temperature covered in the measurements.

Effect of secondary air on soot nucleus production in stoker-fired boilers

Black smoke emission and soot nucleus production in a stoker-fired boiler by secondary air are studied numerically and experimentally. Temperature field, flow field, and soot nucleus concentration are predicted numerically. It reveals that the secondary air gives about 10% reduction of the soot nucleus production, and the black smoke emission is controlled evidently.