The Indian Ocean Experiment (INDOEX) had as a primary objective determining the radiative forcing due to anthropogenic aerosols over climatologically significant space and time scales: the Indian Ocean during the winter monsoon, January-March. During the winter monsoon, polluted, low-level air from the Asian subcontinent blows over the Arabian Sea and Indian Ocean. As part of INDOEX, aerosol optical depths were derived from Advanced Very High Resolution Radiometer (AVHRR) data for the cloud-free ocean regions. The AVHRR radiances were first calibrated using the interior zone of the Antarctic and Greenland ice sheets, which proved to be radiometrically stable calibration targets. Optical depths were derived by matching the observed radiances to radiances calculated for a wide range of optical depths and viewing geometry. Optical depths derived with the AVHRR were compared with those derived with NASA's Aerosol Robotic Network (AERONET) CIMEL instrument at the Center for Clouds, Chemistry, and Climate's Kaashidhoo Observatory, as well as with other surface and shipboard observations taken in the INDOEX region. The retrieved and surface-based optical depths agreed best for a new 2-channel, 2- aerosol model scheme in which the AVHRR observations at O·64 and O·84 microns were used to determine relative amounts of marine and polluted continental aerosol and then the resulting aerosol mixture was used to derive the optical depths. Broadband radiative transfer calculations for the mixture of marine and polluted continental aerosols were combined with the 0·64 and 0·84-micron AVHRR radiances to determine the radiative forcing due to aerosols in the INDOEX region. Monthly composites of aerosol optical depth and top of the atmosphere, surface, and atmospheric radiative forcing were derived from calibrated AVHRR radiances for January-March 1996-2000. An inter-annual variability in the magnitude and spatial extent of high value regions is noted for derived optical depths and radiative forcing, with highest values reached in 1999, particularly in the Bay of Bengal which during the IFP was covered by plumes from Indochina. Frequency distributions of the optical depth for 1⁰ x 1⁰ latitude-longitude regions are well represented by gamma distribution functions. The day-to-day and year-to-year variability of the optical depth for such regions is correlated with the long term average optical depth. Interannual variability of the monthly mean optical depths for such regions is found to be as large as the day to day. / Graduation date: 2001

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Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [133]-142).

Thesis advisor: Cowles, Mary K. Includes bibliographic references (p. 167-172).

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2014-11-10T10:35:23Z No. of bitstreams: 0 / Made available in DSpace on 2014-11-10T10:35:23Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2014-11-10T10:35:23Z No. of bitstreams: 0 / Made available in DSpace on 2014-11-10T10:35:23Z (GMT). No. of bitstreams: 0 / O Programa de Controle de Qualidade de sistemas geradores de raios X inclui a verificação periódica da constância dos feixes de raios X, para tanto é preciso que o físico especialista conheça as respostas dos instrumentos medidores de radiação. Neste trabalho foi analisado o comportamento das câmaras de ionização submetidas a feixes de radiação em Radiodiagnóstico nas energias de 50, 81, 90 e 102 kV. Inicialmente foram realizadas medidas experimentais com oito câmaras de ionização de quatro modelos- e, em seguida, foi simulado através do Método de Monte Carlo, com o código MCNP5, um sistema gerador de raios X e os quatro modelos de câmaras de ionização empregados na parte experimental. Com as simulações de arranjo padronizado foi calculado o valor de kerma no ar e foram comparadas, então, as respostas obtidas experimentalmente com os cálculos por simulação. As correlações obtidas entre os resultados permitiram o desenvolvimento de uma ferramenta que apresenta maiores informações para a compreensão dos equipamentos detectores utilizados, e que auxilia o especialista em física médica na análise da resposta dos detectores. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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A finite-element model describing the dynamic thermal response of an absolute active cavity radiometer is developed. The model considers thermal conduction, diffuse-specular thermal radiation and electrical heat generation. The analysis of diffuse-specular radiation is made possible by the use of the Monte Carlo method. The model is used to analyze both the steady-state and transient instrument response for operating temperatures of 5, 70 and 300 K using a 465-node system. The temperature is monitored at the locations where resistance thermometers would be mounted on thermal impedance members. Steady-state relationships between radiative input energy from a uniform diffuse source field and temperature drop between the resistance thermometers and the heat sink are found to be linear. The steady-state sensitivity of the model to a diffuse input field, determined by relating electrical input energy to radiative input energy, is found to be a function of the placement of the heater wire on the cavity but is independent of operating temperature. The transient response of the instrument to a step increase in radiative input energy is examined in both passive and active operation, and in the latter case with feedback control of the electrical heating. In passive operation, the time constants of the thermal circuit of the model are determined to be 0.35 ms, 5.38 s and 17.80 s for the operating temperatures of 5, 70 and 300 K, respectively. The effects of the electrical substitution heater feedback circuit time constant on overall model performance are determined from closed-loop active operation. Overdamped, underdamped and nearly critically damped model response is obtained for selected values of the electrical circuit time constant. / M.S.

The Earth Radiation Budget Experiment (ERBE) consists of a suite of three scanning and four nonscanning radiometric instruments on each of three satellites which monitor the solar-reflected and Earth-emitted components of the Earth's radiative energy budget. A numerical model has been formulated to study the dynamic behavior and equivalence of the ERBE scanning thermistor bolometer radiometers. The finite-difference method is applied to the detector of the ERBE scanning radiometer to characterize its thermal and electrical dynamic behavior. The thermal analysis confirms the thermal time constant of the instrument claimed by the vendor. The electrical model reveals that the instrument can be very sensitive to spatial variations of the incident thermal radiation. However, the analysis confirms that the hypothesis of equivalence is justified for viewing typical Earth scenes. / Master of Science