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Markowicz, KM, Flatau PJ, Remiszewska J, Witek M, Reid EA, Reid JS, Bucholtz A, Holben B.  2008.  Observations and modeling of the surface aerosol radiative forcing during UAE(2). Journal of the Atmospheric Sciences. 65:2877-2891.   10.1175/2007jas2555.1   AbstractWebsite

Aerosol radiative forcing in the Persian Gulf region is derived from data collected during the United Arab Emirates (UAE) Unified Aerosol Experiment (UAE(2)). This campaign took place in August and September of 2004. The land -sea-breeze circulation modulates the diurnal variability of the aerosol properties and aerosol radiative forcing at the surface. Larger aerosol radiative forcing is observed during the land breeze in comparison to the sea breeze. The aerosol optical properties change as the onshore wind brings slightly cleaner air. The mean diurnal value of the surface aerosol forcing during the UAE2 campaign is about -20 W m(-2), which corresponds to large aerosol optical thickness (0.45 at 500 nm). The aerosol forcing efficiency [i. e., broadband shortwave forcing per unit optical depth at 550 nm, W m(-2) (tau(500))(-1)] is -53 W m(-2) (tau(500))(-1) and the average single scattering albedo is 0.93 at 550 nm.

Vogelmann, AM, Flatau PJ, Szczodrak M, Markowicz KM, Minnett PJ.  2003.  Observations of large aerosol infrared forcing at the surface. Geophysical Research Letters. 30   10.1029/2002gl016829   AbstractWebsite

Studies of aerosol effects on the Earth's energy budget usually consider only the cooling effects at short (solar) wavelengths, but we demonstrate that they also have important warming effects at thermal infrared (IR) wavelengths that have rarely been observed and are commonly ignored in climate models. We use high-resolution spectra to obtain the IR radiative forcing at the surface for aerosols encountered in the outflow from northeastern Asia. The spectra were measured by the Marine-Atmospheric Emitted Radiance Interferometer (M-AERI) from the NOAA Ship Ronald H. Brown during the Aerosol Characterization Experiment-Asia (ACE-Asia). We show that the daytime surface IR forcing are often a few Wm(-2) and can reach almost 10 Wm(-2) for large aerosol loadings. Thus, even the smaller aerosol IR forcing observed here are comparable to or greater than the 1 to 2 Wm(-2) IR surface enhancement from increases in greenhouse gases. These results highlight the importance of aerosol IR forcing which should be included in climate model simulations.

Witek, ML, Teixeira J, Flatau PJ.  2008.  On stable and explicit numerical methods for the advection-diffusion equation. Mathematics and Computers in Simulation. 79:561-570.   10.1016/j.matcom.2008.03.001   AbstractWebsite

In this paper two stable and explicit numerical methods to integrate the one-dimensional (1D) advection-diffusion equation are presented. These schemes are stable by design and follow the main general concept behind the semi-Lagrangian method by constructing a virtual grid where the explicit method becomes stable. It is shown that the new schemes compare well with analytic solutions and are often more accurate than implicit schemes. In particular, the diffusion-only case is explored in some detail. The error produced by the stable and explicit method is a function of the ratio between the standard deviation an of the initial Gaussian state and the characteristic virtual grid distance AS. Larger values of this ratio lead to very accurate results when compared to implicit methods, while lower values lead to less accuracy. It is shown that the sigma(0)/Delta S ratio is also significant in the advection-diffusion problem: it determines the maximum error generated by new methods, obtained with a certain combination of the advection and diffusion values. In addition, the error becomes smaller when the problem becomes more advective or more diffusive. (C) 2008 IMACS. Published by Elsevier B.V. All rights reserved.

Flatau, PJ, Stephens GL.  1988.  On the Fundamental Solution of the Radiative-Transfer Equation. Journal of Geophysical Research-Atmospheres. 93:11037-11050.   10.1029/JD093iD09p11037   AbstractWebsite

This paper outlines the general solution of the one-dimensional, azimuthally averaged radiative transfer equation in terms of a matrix exponential. The link between this fundamental solution and those more commonly used in radiative transfer is established. The formulation is developed for a general vertically inhomogeneous atmosphere with sources. Several new concepts, based on properties of the matrix exponentials, are described in the context of radiative transfer, including the use of the commutator and product integrals. It is also demonstrated how the matrix exponential formulation provides for new insights, not only into improvements of the numerical efficiency and stability of the solution, but also into the understanding of radiative transfer through a layered atmosphere. The various concepts introduced in this paper are illustrated throughout by the two-stream simplification of the general radiative transfer equation.

Maslowska, A, Flatau PJ, Stephens GL.  1994.  On the Validity of the Anomalous Diffraction Theory to Light-Scattering by Cubes. Optics Communications. 107:35-40.   10.1016/0030-4018(94)90099-x   AbstractWebsite

The extinction and absorption efficiencies of a cube at light incidence normal to its four-fold symmetry axis are calculated using the anomalous diffraction theory (ADT). The results are compared with those based on the discrete dipole approximation (DDA). It is shown that for certain cases of the orientation of a cube relative to the direction of the incident light the extinction efficiency calculated using DDA and ADT do not agree. However, the ADT-based absorption efficiencies for the cases studied are dependent on a particle volume and exhibit smaller errors. Hence the validity of the ADT for cubes is not as good as for spheres.

Stramski, D, Wozniak SB, Flatau PJ.  2004.  Optical properties of Asian mineral dust suspended in seawater. Limnology and Oceanography. 49:749-755. AbstractWebsite

The spectral optical properties of Asian mineral dust suspended in seawater exhibit significant variability associated with the origin (and, hence, the chemistry and mineralogy) and particle size distribution of the samples. The measurements of dust samples from different locations show that the mass-specific absorption coefficient of particles, a(p)*, at a wavelength of light lambda = 440 nm, varies from about 0.028 m(2) g(-1) for the soil dust from Chinese desert Pnear Dunhuang to 0.15 m(2) g(-1) for the soil dust of volcanic origin in Cheju Island (South Korea). At lambda = 400 nm, this range is 0.05-0.23 m(2) g(-1). The aerosol sample collected in the Sea of Japan during a massive dust storm in East Asia shows a(p)*(lambda) > 0.1 m(2) g(-1) for lambda < 425 nm. The mass-specific scattering coefficient, b(p)*(lambda), ranges from about 0.8 to 1.5 m(2) g(-1) at blue and green wavelengths for the samples examined. The single scattering albedo, omega(0) increases with wavelength. For lambda > 400 nm, omega(0) was > 0.78 for the sample from Cheju Island and > 0.9 for other samples. In the near-infrared region (750-850 nm), where absorption by dust particles is small or undetectable, omega(0), was close to 1.