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Specular reflection off the ocean surface has been used to derive ocean wave heights and surface wind speeds, but the effect that waves have on ocean surface reflection of incident solar radiation is not fully understood. This study focussed on measuring how sun glint affects the Earth's radiation budget, by including the previously ignored specularly reflecting region. Measurements collected by the GOES-10 geostationary satellite were used to produce an effective sun glint albedo to characterize the accuracy of omitting the glint region from the radiation budget. Estimations were made using the Cox/Munk statistical distribution model. These results varied slightly as a function of wind speed where a 6 m/s surface wind speed produced an effective clear sky sun glint albedo of 1.9%. This value was less than the satellite measured value of 2.2 ± 0.1% for measurements in the cloud free region. Estimates including clouds show a smaller glitter effect of 1.7 ± 0.1%. These values were then extrapolated to the full Earth value by including ocean fraction resulting in global values of 1.6 ± 0.1% and 1.2 ± 0.1% for clear sky and cloudy respectively.

Optical fibers have revolutionized telecommunications. Much of the success of optical fiber lies in its near-ideal properties: low transmission loss, high optical damage threshold, and low optical nonlinearity. The photosensitivity of an optical fiber was accidentally discovered by Hill, et al. in 1978. However, the technological advances made in the field of photosensitive optical fibers are relatively recent. This fascinating technology of photosensitive fiber is based on the principle of a simple in-line all-fiber optical filter. It has been shown that the transmission spectrum of a fiber Bragg grating can be tailored by incorporating multiple phase-shift regions during the fabrication process. Phase shifts open up ultra narrowband transmission windows inside the stop band of the Bragg grating. As a specific application, this research is focused on applying this technology in future space-based water vapor DIfferential Absorption LIDAR (DIAL) systems to improve the performance of space-based LIDAR systems by rejecting the reflected solar background. The primary goal of this research effort was to demonstrate the feasibility of using ultra narrow band fiber optic Bragg grating filters for atmospheric water vapor measurements. Fiber Bragg gratings were fabricated such that two transmission filter peaks occurred and were tunable, one peak at a 946 nm water vapor absorption line and another peak at a region of no absorption. Both transmission peaks were in the middle of a 2.66-nm stop band. Experimental demonstration of both pressure and temperature tuning was achieved and characterization of the performance of several custom-made optical fiber Bragg grating filters was made. To our knowledge these are the first optical fiber gratings made in this frequency range and for this application. The bandwidth and efficiency of these filters were measured and then these measurements were compared with theoretical calculations using a piecewise matrix form of the coupled-mode equation. Finally, an ultra narrow band water vapor DIAL filter was characterized having two pass bands less than 8 pm and peak transmissions greater than 80 percent. Such fiber optic filters are now ready for integrating into space-based water vapor LIDAR systems. More broadly, these filters have the characteristics that will revolutionized satellite remote-sensing.

This dissertation investigated the estimation of global cloud water amounts. The study was prompted by the large discrepancy in published global mean values of cloud liquid water path. Microwave and optical satellite measurements of this quantity range from 25 g/m² to 80 g/m². Theoretical estimates are significantly larger with a current best guess value of 380 g/m². The major limitations of microwave measurements were found to be the inadequate separation of the cloud- and rainwater components, and the lack of retrievals over land. Optical observations were found to be constrained by the truncation of retrieved optical thickness due to saturation effects, the limited knowledge of drop effective radius as a function of optical thickness and rain rate, and plane-parallel retrieval errors due to 3D effects. An analysis of the potential uncertainties concluded that the current theoretical estimate of the global mean cloud liquid water path of 380 g/m² was reasonable with an uncertainty of ±80 g/m². Errors in the optical retrievals due to 3D effects were estimated using a multiangle data set. A microwave-optical comparison revealed that a drop effective radius significantly larger than the common assumption of 8-10 μm was required to remove the low bias of optical retrievals of cloud liquid water in precipitating systems. The low bias due to saturation effects was accounted for by sigmoidal extrapolation of the cumulative distribution of cloud optical thickness. Overall it was found that the optical measurement of the global mean cloud liquid water path could be increased to a maximum of 150 g/m² over the oceans. The failure to close the gap between satellite measurements and theoretical estimates can partly be attributed to, but cannot be completely explained by, the lack of the most intense continental clouds in the ocean-only data set used in this study. It is unlikely that optical measurements can be corrected to accurately retrieve the largest liquid water amounts. New techniques are required to handle the wettest precipitating clouds.

Measurements of the refractive bending of solar radiation passing through the limb of the Earth's atmosphere can be utilized to recover vertical profiles of density and temperature. These parameters obtained using the technique of solar refractive sounding could be used to improve satellite solar occultation trace species retrievals and to monitor potential trends in upper atmospheric temperatures. The solar refractive sounding method is described in detail and applied to data available from the Stratospheric Aerosol and Gas Experiment (SAGE II). The meteorological profiles derived from the SAGE II data are not consistently accurate enough for general use due to poor vertical sampling and measurement uncertainties. However, the qualitatively decent results provide optimism for future development and implementation of solar occultation refractive sounders. Better techniques for measuring solar refraction and the potential improvements in the retrievals are also discussed.

The First Negative (1N) band emission of the molecular nitrogen ion, N⁺₂ , is one of the most prominent features of the terrestrial dayglow spectrum. However, past N⁺₂ studies have encountered problems in validating the intensity of this emission. Also, some anomalous characteristics of the dayglow 1N spectrum remain unexplained, such as a highly developed rotational and vibrational structure. These anomalies appear to be due to the charge exchange reaction: O⁺ + N₂ → N⁺₂ + O, which dominates N⁺₂ ion production at high altitudes. This thesis examines dayglow 1N spectra acquired by the Arizona Airglow Experiment (GLO) flown on the space shuttle mission STS-74. In the analysis the emission is separated into two components. First is the emission from ions produced by photoionization and electron bombardment. Second is emission from ions produced by the charge exchange reaction, which cannot be modeled. The first source is evaluated and subtracted from the observed spectrum. The remaining emission is then used to derive empirical parameters related to the charge exchange reaction. These parameters can be used to estimate the 1N emission rate expected from the thermosphere, based on model atmosphere predictions. This emission rate can be used to determine the dayside O⁺ concentration using the GLO observations.

It has been recognized that pollution (sulfate aerosols), and biomass burning (smoke aerosols), are the two principal anthropogenic sources that are now influencing the global climate. Researchers are currently trying to provide better estimates of the climate impact due to anthropogenic aerosols and to lower the range of uncertainty in their calculations. Estimations suggest a global-mean direct radiative forcing in the range from -0.3 to -1.0 W/m² for biomass burning aerosols, with a similar value for the indirect effect. The primary goal of this work is to estimate the global climate impact due to smoke aerosols from biomass burning using the National Center for Atmospheric Research (NCAR)-Community Climate Model, Version 3 (CCM3). Analysis of data from the AERONET project was used to define a more realistic average of the optical/radiative properties of smoke particles from biomass burning in the Amazon, and also, to provide relevant information about the cloud-aerosol interactions. This information was put into the context of the NCAR-CCM3 BATS, and then the cloud/radiative scheme of the standard model was modified to include both the direct and indirect effects of the aerosols. Our results suggest an annual global mean "total" (direct+indirect) radiative forcing of about -0.08 W/m². This value is in good agreement with recent estimations considering that we are only including the biomass burning aerosols in the Amazon region. In addition, our model simulations provide a "total" radiative forcing of about -10 W/m² for the Amazon region during the dry-season, where the indirect effect is responsible for about 80% of this value. This research hopefully will contribute to the aerosol climate modeling area by providing a scheme in which both the direct and indirect effects of the aerosol can be explicitly represented in a GCM.

Aerosols have been identified as a major element of the climate system known to scatter and absorb solar and infrared radiation, but the development of procedures for representing them is still rudimentary. This study addresses the need to improve the treatment of sulfate aerosols in climate models by investigating how sensitive radiative particles are to varying specific sulfate aerosol properties. The degree to which sulfate particles absorb or scatter radiation, termed the direct effect, varies with the size distribution of particles, the aerosol mass density, the aerosol refractive indices, the relative humidity and the concentration of the aerosol. This study develops 504 case studies of altering sulfate aerosol chemistry, size distributions, refractive indices and densities at various ambient relative humidity conditions. Ammonium sulfate and sulfuric acid aerosols are studied with seven distinct size distributions at a given mode radius with three corresponding standard deviations implemented from field measurements. These test cases are evaluated for increasing relative humidity. As the relative humidity increases, the complex index of refraction and the mode radius for each distribution correspondingly change. Mie theory is employed to obtain the radiative properties for each case study. The case studies are then incorporated into a box model, the National Center of Atmospheric Research's (NCAR) column radiation model (CRM), and NCAR's community climate model version 3 (CCM3) to determine how sensitive the radiative properties and potential climatic effects are to altering sulfate properties. This study found the spatial variability of the sulfate aerosol leads to regional areas of intense aerosol forcing (W/m²). These areas are particularly sensitive to altering sulfate properties. Changes in the sulfate lognormal distribution standard deviation can lead to substantial regional differences in the annual aerosol forcing greater than 2 W/m². Changes in the aerosol chemical composition can lead to regional changes in the aerosol forcing greater than 0.5 W/m². The relative humidity is shown to greatly influence the aerosol optical properties. Given the differences in aerosol forcing found due to varying sulfate properties, this study does not encourage the use of a single aerosol distribution to represent sulfate particles of all air masses.

Atmospherically-relevant surface reactions were studied. These reactions were investigated to provide insight into the products formed on sea salt atmospheric particle surfaces, the quantitative distribution of species on the surface of model sea salt particles, and the molecular environment of the interfacial region of HNO₃/H₂O ices. The reactions of model sea salt particles (NaCl) exposed to mineral acids (HNO₃ and H₂SO₄) were studied using Raman spectroscopy and atomic force microscopy (AFM). The reaction of powdered NaCl with HNO₃ was studied using Raman spectroscopy. NaNO₃ growth was monitored as a function of HNO₃ exposure in a flow cell. Mode-specific changes in the NO₃- vibrational mode intensities with HNO₃ exposure suggest a rearrangement of the NaNO₃ film with coverage. In the absence of H₂O, intensities of NaNO₃ bands increase with HNO₃ exposure until a capping layer of NaNO₃ forms. The capping layer prevents subsequent HNO₃ from reacting with the underlying. The reaction of NaCl with H₂SO₄ is investigated using Raman spectroscopy and atomic force microscopy (AFM). Raman spectra are consistent with the formation of NaHSO4 with no evidence for Na₂SO₄. The spectra indicate that the phase of NaHSO₄ varies with the amount of H₂O in the H₂SO₄. The reaction produces anhydrous β-NaHSO₄ which undergoes a phase change to anhydrous α-NaHSO₄. AFM measurements on NaCl (100) show the formation of two distinct types of NaHSO4 structures consistent in shape with α-NaHSO₄ and β-NaHSO₄ . Model sea salt particles were gown from solution to determine the surface Br/Cl of crystals grown from solution. These studies show surface Br concentration is 35 times that of the bulk concentration. This data is useful in the understanding of enhanced volatile Br compounds in the Arctic troposphere. Thin films of model polar stratospheric cloud (PSC) surfaces were studied in ultrahigh vacuum. Low temperature data show the preferential orientation of HNO₃ on crystalline H₂O ice. Thermodynamically-stable HNO₃ · 3H₂O is formed at ∼170 K, and subsequently desorbs from the surface. These studies show the chemical specificity of Raman spectroscopy in this chemical system. Studies of ClONO₂ adsorption onto crystalline H₂O ice suggest that ClONO₂ is weakly adsorbed.

A new method of calculating accurate visible radiance values in the solar aureole region is derived in this study. The method interpolates between the radiance values output by a Gauss-Seidel flat atmosphere radiative transfer model using the radiative transfer equation itself. The method thereby produces accurate radiance values for arbitrary directions with only a slight increase in the required computational effort. The radiance and diffuse irradiance are then calculated for a variety of specified model atmospheres. The impact of polarization and the vertical stratification of aerosol particles is also investigated under various atmospheric conditions, and found to be relatively small under most realistic conditions. It is also found that some care must be taken when choosing the maximum aerosol radius at which to truncate the aerosol size distribution employed in the model atmosphere, to ensure that one does not exclude significant contributors to the scattered radiance field.