The purpose of following project is to study the effect of dust aerosols on the radiative forcing which is directly related to the surface temperature. A single column radiative convective model is used for simulation purpose. A series of simulations have been performed by varying the amount of dust aerosols present in the atmosphere to study the trends in ground temperature, heating rate and radiative forcing for both its longwave and shortwave components. A case study for dust storm is also performed as dust storms are common in Arabian Peninsula. A sensitivity analyses is also performed to study the relationship of surface temperature minimum and maximum against aerosol concentration, single scattering albedo and asymmetry factor. These analyses are performed to get more insight into the role of dust aerosols on radiative forcing.

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This work embraces the measurement of angular distributions and excitation functions for proton radiative capture to the ground and excited states of 13N, in energy steps from E p = 40 to E p = 52MeV. Legendre polynomial fits to the angular distributions are made and the energy variation of Legendre coefficients is established for several (p, 7 ) transitions involving states up to an excitation energy of 15 MeV. The polynomial coefficients are explained by large dipole-quadrupole interference effects, particularly interesting at excitation energies corresponding to twice (£„ ~ 46 MeV) the centroid value of the ground state based Giant Dipole Excitation. Broad resonances are found in the (p,7o) &nd the (p, 72+3) channels, which involve final states that are members of the same rotational band and therefore should present very similar internal structures as the almost equivalent Legendre coefficients substantiate. For other excited states similar trends have been found although within limits imposed by larger experimental errors. The 2hw -+ Ihuj transition is found largely superimposed on inelastic proton scattering channels, contrary to what was established in previous experiments. Upper limits for the excitation functions are extracted and only for the highest measured energy point are the two contributions clearly separated. This reasearch program is based on a newly-developed anti-coincidence large-volume scintillation spectrometer designed by means of a Monte Carlo simulation code. Sp jcific tests performed with Tandem accelerator beams, and routine application at higher energies, demonstrate the excellent correspondence of the design expectations with the performance as measured, for this spectrometer.

Graduation date: 1994

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 85-88). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Chicago, Dept. of the Geophysical Sciences, March 1999. / Includes bibliographical references. Also available on the Internet.

We solve the equations of radiation hydrodynamics to compute the time evolution toward one-dimensional equilibrium solutions using ageneralized Kramers opacity, κ=κ0 ρa Tb, with adjustable prefactor κ0 and exponents a and b on density ρ and temperature T, respectively. We choose our initial conditions to be isothermal and find that the early time evolution away from the isothermal state is fastest near the height where the optical depth is unity, and is slower both above and below it. In all cases where the quantity n=(3-b)/(1+a) is larger than -1, we find a nearly polytropic solution with ρ<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Cpropto" />Tn in the lower part and a nearly isothermal solution in the upper part with a radiating surface in between, where the optical depth is unity. In the lower part, the radiative diffusivity is found to be approximately constant, while in the upper optically thin part it increases linearly. Interestingly, solutions with different parameter combinations a and b that result in the same value of n are rather similar, but not identical. Increasing the prefactor increases the temperature contrast and lowers the value of the effective temperature. We find that the Péclet number based on sound speed and pressure scale height exceeds numerically manageable values of around 104 when the prefactor κ0 is chosen to be approximately six orders of magnitude below the physically correct value. In the special case where a=-1 and b=3, the value of n is undetermined and the radiative diffusivity is strictly constant everywhere. In that case we find a stratification that is approximately adiabatic. Finally, exploratory two-dimensional calculations are presented where we include turbulent values of viscosity and diffusivity and find that onset of convection occurs when these values are around 3<img src="http://www.diva-portal.org/cgi-bin/mimetex.cgi?%5Ctimes" />1013 cm2 s-1. The addition of an imposed horizontal magnetic field suppresses small-scale convection, but has not led to instability in the cases investigated so far.