Vertical profiles of optical and microphysical characteristics of tropospheric aerosol from aircraft measurements

Abstract

According to the International Panel on Climate Change (IPCC), the current lowest level of scientific understanding in estimates of radiative forcings of different atmospheric constituents is assigned to aerosols (Forster et al., 2007;Hansen et al., 2005), primarily due to a few factors.The first factor is associated with the difficulty in obtaining accurate quantitative information on the required parameters and is caused by (i) strong spatiotemporal variations of the sources and sinks of aerosol particles, (ii) relatively short lifetimes (approximately 7 days) in the troposphere in contrast to greenhouse gases, requiring far more detailed knowledge of their spatiotemporal variations, and (iii) the difficulty in performing synchronous measurements of the scattering and absorbing properties of aerosols for studying their vertical and horizontal distributions.The second complex problem is associated with the multiform impact of atmospheric aerosols on Earth's radiation budget, which is manifested by both direct and indirect aerosol effects (Haywood and Boucher, 2000).The direct aerosol effect is the contribution to the cooling (heating) of the atmosphere by aerosol particles, which scatter (absorb) the solar radiation in the atmosphere. Thus, the net effect depends on the relationship between the scattering and absorbing properties of aerosols in the atmospheric column (Penner et al., 2003;Haywood and Ramaswamy, 1998). The indirect aerosol effects are more complex (Twomey, 1977b;Albrecht, 1989;Johnson et al., 2004). The aerosol particles, acting as condensation nuclei, determine the amount of cloud droplets and their microstructure, thus affecting both the optical properties of clouds and their lifetime in the atmosphere. Low-level clouds, as a rule, play a cooling factor role, while clouds at high altitudes can cause a cooling effect, as well as the intensification of atmospheric heating. Another problem is estimating the radiation effects caused by the presence of absorbing aerosol between cloud particles.Still another aspect of the indirect aerosol effect is associated with the sedimentation and settling of aerosol (primarily black carbon (BC)) particles, causing a change in the reflectance (albedo) of the underlying surface. The effect of this process is most significant for the northern territories, where the supply of absorbSpringer-Verlag Berlin Heidelberg 2016 ©

Separate retrieval of microphysical parameters in aerosol fraction from the lidar data

“…Both direct and indirect climate impacts are still not completely understood and may be the greatest source of errors in attempting to make future climate change predictions [7]. To quantify the direct effect, spatial-temporal information about the aerosol optical properties, the optical depth and the single-scattering albedo ω(λ i ) [8][9][10], is important. When quantifying the indirect effect, the aerosol microphysical characteristics, the complex refractive index m = m real + i*m image , and the particle size distribution function U(r) = r d r dV ln ) ( = U fine (r) + U coarse (r) must be taken into account [11][12][13][14].…”