|Monogr. Environ. Earth Planets, Vol. 3 (No. 1), pp. 1-85, 2015||doi:10.5047/meep.2015.00301.0001 ISSN: 2186-4853|
Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113-0033, Japan
(Received June 30, 2014; Revised November 14, 2014; Accepted November 17, 2014; Online published April 30, 2015)
Citation: Kondo, Y. (2015), Effects of black carbon on climate: Advances in measurement and modeling, Monogr. Environ. Earth Planets, 3, 1-85, doi:10.5047/meep.2015.00301.0001.
Abstract: Black carbon (BC) particles are non-spherical agglomerates consisting of hundreds or thousands of graphitic carbon spherules the diameters of which are about 15–50 nm. The spherules are graphitic in their molecular states and are, thus, strongly light-absorbing. BC particles are emitted by the incomplete combustion of carbon-based fossil fuels and biomass. BC mass in the atmosphere resides in agglomerates typically between 100 and 600 nm in diameter. They influence the global radiation budget by strongly absorbing solar radiation in the visible wavelengths and by changing the albedo of snow through deposition. Radiative forcing (RF) of BC is defined as the change in net radiative flux at the top of the atmosphere in W m-2 due to a change of BC between the pre-industrial time and present-day periods. The instantaneous direct radiative forcing of airborne BC particles (BC DRF), which does not include climate feedbacks, is determined by their absorption cross sections and spatial distributions. The distributions of BC are, in turn, controlled by its emission, dynamical transport, and loss during transport. The absorption cross section of BC is controlled by its optical properties (i.e., refractive index) and microphysical properties (size distribution, morphology, and mixing state). Because it is crucial to characterize these parameters, we first developed techniques to measure them accurately. Newly-developed BC measurement technologies constitute the firm basis of our studies. The techniques were applied to laboratory experiments and field observations of BC particles in air and rainwater. We also developed regional scale three-dimensional (3D) models to quantitatively interpret the observational results. One of the models calculates BC aging and optical/radiative processes explicitly without parameterizations. The reliable field measurements and model calculations of BC has enabled an improved understanding of the physical and chemical processes that control the microphysical properties of BC. We also quantitatively analyzed the emission rate, transport, and wet removal processes of BC in Asia by comparing the observed, and model-calculated, BC distributions. Through aircraft measurements in the Arctic, we characterized emissions of BC from biomass burning and the strong seasonal variations of the efficiency of transport of BC from different regions in the northern hemisphere to the Arctic. A number of findings, brought about by the observational and modeling efforts, demonstrate the strength of our innovative methodologies for improving the estimate of BC DRF, which has been highly uncertain thus far.
Keywords: Black carbon, Aerosols, Absorption, Scattering, Radiative forcing, Observations, Modelling, Emission, Transport, Wet depositon.
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