Black carbon: Atmospheric measurements and radiative effect.
Date
1996
Authors
Kou, Linhong.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
Atmospheric black carbon concentrations have been measured in air, cloud, rain and snow samples collected over Nova Scotia during the Radiation, Aerosol, Cloud Experiment (RACE) of 1995. Atmospheric aerosol samples for black carbon analyses were collected by filtering a known amount of air or liquid dispersons (cloud water, rain or melted snow) through quartz filters, and the filters were later subjected to thermo-optical analyses for black carbon determination. The average black carbon atmospheric concentration found in air was $\rm 0.13\pm 0.01\mu g/m\sp3$ at an altitude between 100 and 1700m: $\rm 0.22 \pm 0.02\mu g/m\sp3$ at near-sea surface; and $\rm 0.54 \pm 0.03\mu g/m\sp3$ in summer and $\rm 1.69 \pm 0.08\mu g/m\sp3$ in winter over Halifax area. The black carbon to SO$\sb4\sp{-2}$ mass mixing ratio was found to be 14% over all the samples collected during RACE and the typical black carbon mass fraction in total aerosol is 1-2%. About 6% of black carbon was in the form of an internal mixture inside cloud droplets. The average black carbon content found in cloud water was about $\rm 26\pm 3\mu$g/kg. The average black carbon content was $3.2\pm 0.2\mu$g/kg in rain, and $\rm 8.8\pm 0.4\mu$g/kg in snow over all the samples collected in both rural and urban areas.
The radiative effect of black carbon is discussed in the present study. The black carbon radiative effect is significant compared with sulfate aerosol effect. Black carbon aerosols act to reduce the cooling effect of sulfate aerosols. The reduction of the cooling depends on both the black carbon fraction and the surface albedo. For instances of high surface albedo or high black carbon loading a net heating can result. The results for the Quebec forest fire day show that the black carbon aerosol decreases the sulfate aerosol cooling effect by 20 to 50%. The impact of black carbon aerosol on the radiative properties of clouds is insignificant over the Nova Scotia region.
Thesis (Ph.D.)--Dalhousie University (Canada), 1996.
The radiative effect of black carbon is discussed in the present study. The black carbon radiative effect is significant compared with sulfate aerosol effect. Black carbon aerosols act to reduce the cooling effect of sulfate aerosols. The reduction of the cooling depends on both the black carbon fraction and the surface albedo. For instances of high surface albedo or high black carbon loading a net heating can result. The results for the Quebec forest fire day show that the black carbon aerosol decreases the sulfate aerosol cooling effect by 20 to 50%. The impact of black carbon aerosol on the radiative properties of clouds is insignificant over the Nova Scotia region.
Thesis (Ph.D.)--Dalhousie University (Canada), 1996.
Keywords
Physics, Atmospheric Science., Environmental Sciences.