In this study, heterogeneous chemical reactions between trace gases and atmospheric soot particles are investigated using a particle-resolved aerosol model. The model accounts for physical and chemical processes in the atmosphere that change both particulate and gas phase composition. Four reactive gases, namely the major atmospheric oxidants O3, NO2, OH, and NO3, are considered to compete with non-reactive water vapor for active surface sites on the soot particles coated with polycyclic aromatic hydrocarbons (PAHs). For this purpose, the state-of-the-art particle-resolved aerosol model PartMC-MOSAIC (Particle Monte Carlo model, coupled to the MOdel for Simulating Aerosol Interactions and Chemistry) has been extended to include heterogeneous chemical kinetics based on the recently developed Poeschl-Rudich-Ammann (PRA) framework. PartMC-MOSAIC enables us to model continuous soot emissions with a realistic particle size distribution and to track each particle’s composition individually over the course of a 24 hour simulation. The flux-based approach of the PRA framework accounts for dynamic changes in the uptake of gas species on particle surfaces, which are caused by changes of gas phase and particle composition and associated modification of surface properties. Thus, it is possible to assess in detail the effects of heterogeneous reactions between major atmospheric oxidants and PAH coated soot surfaces on gas phase composition, on uptake kinetics, and on degradation of particle-bound PAHs in atmospherically relevant scenarios. In contrast to previous modeling results we found no significant impact of these reactions on gas phase composition, regardless of the magnitude of soot emissions. Reactive uptake of O3 and NO2 is found to decrease by several orders of magnitude in the first minute of a particle’s atmospheric lifetime but to stay relatively constant thereafter. This is in agreement with the results of previous applications of the PRA framework and experimental data. In case of OH and NO3, uptake coefficients vary with the degree of PAH degradation. They are higher than those for O3 and NO2 during day (&sim； 10-1 to &sim； 10-4 vs. &sim； 10-7 to &sim； 10 -5), but may be significantly lower at night (as low as &sim； 10 -9), when particle-bound PAHs are very efficiently depleted by reaction with NO3. PAH lifetime is on the order of minutes during day, when it is determined mainly by O3, which is about an order of magnitude lower than other laboratory and modeling studies suggested. During night, when NO3 levels are high, the PAH coating is oxidized within seconds, in agreement with experimental results. This study is the first to assess heterogeneous kinetics in atmospheric systems employing a particle-resolved aerosol model, and the complexity of the considered scenarios exceeds that of previous laboratory experiments and modeling studies. The results presented here allow for a much improved evaluation of the role of soot, one of the most ubiquitous types of atmospheric particles, on atmospheric gas phase composition and of its impact on health related issues and climate.

Environmental measurements are complicated by uncontrollable natural variations in the environment, which cannot be reproduced in the laboratory. These variations affect the measurement uncertainty and detection capabilities — two measures of data quality. Variations in a measurement series that arise from uncertainty in the measurements should not be interpreted as variations in the environment. Accurate estimates of measurement uncertainty are thus important inputs to data analyses. Collocated duplicate) measurements are the most direct approach to characterizing uncertainty and detection capabilities because the observed differences reflect the actual measurement performance under the natural environmental variability. This dissertation uses collocated measurements of airborne particulate matter chemical speciation collected by the Interagency Monitoring of Protected Visual Environments IMPROVE) and Speciation Trends Network STN) to explore data quality issues. In addition to the complications introduced by uncontrollable environmental factors, the concepts of measurement precision and detection capabilities are often complicated by incomplete and inconsistent definitions. In this dissertation, collocated IMPROVE data are used to illustrate different formulations for precision and their ability to fit the observed differences. Collocated IMPROVE data are also used to show that measurement precision is typically better at concentrations well above the detection limit, when the analysis is performed on the whole filter instead of just a fraction of the filter, and for species predominantly in the smaller size fractions. For most species, the collocated differences are worse than the differences predicted by the current uncertainty model, suggesting that some sources of uncertainty are not accounted for or have been underestimated in the model. In addition, collocated measurement differences are shown to be correlated among several species. In both IMPROVE and STN, obvious correlations exist among differences in elements associated with soil dust, which are dominated by particles with diameters ＞ 1 mum. These correlations suggest the current model is missing significant sampling errors associated with the size discrimination operation. Measurement uncertainty generally increases as concentrations approach the detection limit. This dissertation introduces an empirical approach for estimating detection limits using collocated IMPROVE and STN data that accounts for the natural variations in the environment.

Presented herein is an investigation of quantum systems with coherent optical control fields. Three such systems are examined. The first consists of two dipole-dipole coupled quantum dots or dimers which behave as an effective three or four-level system whose susceptibility and hence transmissivity for an optical beam at some frequency may be switched on or off in response to a coherent control field. The second quantum system consists of a model cluster of three coupled dots that is shown to display light intermittency or blinking when irradiated by a coherent field. Results indicate that the observed variation in rate, intensity and duration of blinking times occasioned by the rare but observable rapid blinking at higher rate and intensity (superradiance) can be traced back to the groupings of states in different manifolds that the coupled system is capable of being found in at any given time. It is shown, however, that the experimentally observed blinking can not be entirely accounted for by dipole-dipole coupling alone. The third system investigated consists of Rubidium atoms in a cell placed in a ring cavity. A coherent control field drives the system. A mathematical model of the system is developed which consists of propagating a gaussian beam around the system and examining the output spectrum when a steady state value of the electromagnetic field is attained in the Rubidium cell. Some interesting features occurring in the output spectrum of the field at some cavity detuning are reproduced and match those experimentally observed.

Numerical algorithms are proposed, analyzed and tested for improved efficiency and reliability of the dynamic core of climate codes. The commonly used rigid lid hypothesis is assumed, which allows instantaneous response of the interface to changes in mass. Additionally, moisture transport is ignored, resulting in a static interface. A central algorithmic feature is the numerical decoupling of the atmosphere and ocean calculations by a semi-implicit treatment of the interface data, i.e. partitioned time stepping. Algorithms are developed for simplified continuum models retaining the key mathematical structure of the atmosphere-ocean equations. The work begins by studying linear parameterization of momentum ux in terms of wind shear, coupling the equations. Partitioned variants of backward-Euler are developed allowing large time steps. Higher order accuracy is achieved by deferred correction. Adaptations are developed for nonlinear coupling. Most notably an application of geometric averaging is used to retain unconditional stability. This algorithm is extended to allow different size time steps for the subcalculations. Full numerical analyses are performed and computational experiments are provided. Next, heat convection is added including a nonlinear parameterization of heat flux in terms of wind shear and temperature. A partitioned algorithm is developed for the atmosphere and ocean coupled velocity-temperature system that retains unconditional stability. Furthermore, uncertainty quantification is performed in this case due to the importance of reliably calculating heat transport phenomena in climate modeling. Noise is introduced in two coupling parameters with an important role in stability. Numerical tests investigate the variance in temperature, velocity and average surface temperature. Partitioned methods are highly efficient for linearly coupled 2 fluid problems. Extensions of these methods for nonlinear coupling where the interface data is processed properly before passing yield highly efficient algorithms. One reason is due to their strong stability properties. Convergence also holds under time step restrictions not dependent on mesh size. It is observed that two-way coupling requiring knowledge of both atmosphere and ocean velocities on the interface) generates less uncertainty in the calculation of average surface temperature compared to one-way models only requiring knowledge of the wind velocity).

Extra tropical cyclones (also sometimes called middle-latitudes cyclones outside of tropics) in the Northern Hemisphere are generally generated from 30 to 60 degrees North latitudes. Higher latitudes cyclones, also called Arctic cyclones, are generally generated from 60 to 90 degrees North latitudes. It has been felt that there is an uptrend of these extra tropical cyclones moving North over time during their movement from starting latitudes to the ending latitudes. In this research, an attempt has been made to investigate this uptrend of the cyclones based on the data called ERA40 North Hemispheric cyclone tracking data provided by Environment Canada for 44 years (1958-2001). The present study has been concentrated in the North American Region.

The accuracy of hurricane intensity forecasts has lagged the accuracy of hurricane track forecasts thereby creating a need for improvement. Many models struggle capturing the rapid intensification period and identifying when it will occur which causes a large amount of error in the intensity forecasts. The method described in this paper uses a discriminant function analysis DFA) to help identify how intense the tropical cyclone will become and also how close it is to the rapid intensification period. Identifying the proximity to the rapid intensification period is a key factor in improving the intensity forecasts. Based upon the intensity and its proximity to its rapid intensification period, as selected by the DFA, an appropriate regression model is applied to forecast the 24-hour and 6-hour pressure reduction and wind speed increase. Other statistical intensity models apply the same regression model throughout the entire lifecycle of the tropical cyclone. This model relies on the premise that factors which cause intensification affect the tropical cyclone differently throughout its life cycle. Therefore, by using the DFA, different stages in its life cycle are identified, which allows the regression model to use the most significant variables at the particular stage. They are shown to improve the intensity forecasts at the stages leading up to and during the rapid intensification, which happen to be the most difficult stages to predict. The forecasts were validated with 13 independent case studies and compared with the official National Hurricane Center NEC) forecasts.

The aerosol indirect effect remains one of the most important uncertainties in the projection of future climate. Here we first provided an observational evidence of the change in radiative forcing due to the aerosol indirect effect. Based on the observations of aerosol and cloud properties, we used a cloud parcel model to estimate the cloud optical depth at a polluted site and a clean site. We also determined the cloud optical depth required to fit the surface measured downward SW fluxes. Results from both methods show that the cloud optical depth is larger at the polluted site given a value of cloud liquid water path. From this good agreement we concluded that the aerosol indirect effect has a significant influence on the radiative fluxes. Then, we used 3-D meteorological fields together with a radiative transfer model to calculate the global first aerosol indirect forcing. We also examined the spatially-resolved uncertainty in estimates of this forcing by perturbing the values of each parameter in the calculation. The global mean forcing calculated in the reference case is -1.30 Wm-2, and the global mean relative uncertainty is 130%. The aerosol burden calculated by chemical transport models and the cloud fraction were found to be the most important sources of uncertainty. We also studied the aerosol indirect effect by nitrate and nitric acid gas. The indirect effect of nitrate on TOA radiative flux was found to be comparable to that by anthropogenic sulfate in some places. A substitution method that accounts for the gas phase nitric acid effect on CCN activation was developed and added to the cloud nucleation parameterization. Anthropogenic aerosols may also change the formation of ice crystals in cirrus clouds, which has effects on both the SW and LW radiative balance of the earth. The indirect forcing due to anthropogenic aerosols was calculated by a radiative transfer model using aerosols from different emissions. The results show that anthropogenic aerosols may have two effects on cirrus clouds: increase in the ice number concentration Ni) by increasing the ice nuclei concentration, or decrease Ni by lowering the maximum supersaturation.

Large-scale atmospheric circulation regimes across much of the globe are determined by quasi-stationary Rossby waves. Rossby waves propagate linearly in the presence of a westerly jet and a strong latitudinal gradient of potential vorticity PV). However, as a Rossby wave train propagates toward lower latitudes and encounters weak ambient winds, the flow becomes highly nonlinear and wave breaking may occur. Planetary wave breaking PWB) is defined as the rapid, large-scale and irreversible quasi-horizontal overturning of PV contours on isentropic surfaces. Among the implications of PWB is the possibility of nonlinear reflection following the breaking event. While identified in analytical and modeling studies, the first observational evidence of nonlinear reflection is presented. PWB is found to be a ubiquitous feature year-round in the upper troposphere and in the stratospheric winter hemisphere. Daily reanalysis datasets are used to identify PWB in two main regions: the subtropical upper troposphere, and along the periphery of the stratospheric vortex. The subtropical jet and wave forcing are found to play key roles in determining both the annual cycle as well as the interannual/intraseasonal variability of tropospheric PWB. Nonlinear reflection is identified in a subset of all PWB events. In the troposphere, reflection is characterized by a poleward arching wave train downstream of the breaking region and back into midlatitudes. The absorptive-reflective outcome of wintertime PWB over the North Atlantic basin strongly impacts the intraseasonal North Atlantic Oscillation NAO). For non-reflective events, the absorption of wave activity amplifies the regional poleward eddy momentum flux and the positive phase of the NAO. Conversely, the reflection of wave activity out of the North Atlantic basin leads to a reversal of both the regional poleward eddy momentum flux and the phase of the NAO. In the stratosphere, the reflection of wave activity toward the pole leads to a strong deceleration at high latitudes and forces the stratospheric Northern Annular Mode NAM) into a negative phase. These anomalies propagate downward in the following weeks and induce the negative phase of the tropospheric NAM.

Particle size and composition are key factors controlling the impacts of particulate matter (PM) on human health and the environment. A comprehensive method to characterize size-segregated PM organic content was developed, and evaluated during two field campaigns. Size-segregated particles were collected using a cascade impactor (Micro-Orifice Uniform Deposit Impactor) and a PM2.5 large volume sampler. A series of alkanes and polycyclic aromatic hydrocarbons (PAHs) were solvent extracted and quantified using a gas chromatograph coupled with a mass spectrometer (GC/MS). Large volume injections were performed using a programmable temperature vaporization (PTV) inlet to lower detection limits. The developed analysis method was evaluated during the 2001 and 2002 Intercomparison Exercise Program on Organic Contaminants in PM2.5 Air Particulate Matter led by the US National Institute of Standards and Technology (NIST). Ambient samples were collected in May 2002 as part of the Tampa Bay Regional Atmospheric Chemistry Experiment (BRACE) in Florida, USA and in July and August 2004 as part of the New England Air Quality Study – Intercontinental Transport and Chemical Transformation (NEAQS – ITCT) in New Hampshire, USA. Morphology of the collected particles was studied using scanning electron microscopy (SEM). Smaller particles (one micrometer or less) appeared to consist of solid cores surrounded by a liquid layer which is consistent with combustion particles and also possibly with particles formed and/or coated by secondary material like sulfate, nitrate and secondary organic aerosols. Source apportionment studies demonstrated the importance of stationary sources on the organic particulate matter observed at these two rural sites. Coal burning and biomass burning were found to be responsible for a large part of the observed PAHs during the field campaigns. Most of the measured PAHs were concentrated in particles smaller than one micrometer and linked to combustion sources. The presence of known carcinogenic PAHs in the respirable particles has strong importance for human health. Recommendations for method improvements and further studies are included.

This thesis reports experimental and theoretical studies of the spectroscopy and kinetics of four atmospheric reservoir species: peroxynitrous acid HOONO), peroxyacetyl nitrate PAN, CH3CO)OONO2), methyl hydroperoxide MHP, CH3OOH), and hydroxymethyl hydroperoxide HMHP, HOCH 2OOH). Reservoir species are so named because they temporarily or permanently sequester reactive radicals such as OH, HO2, or NO2), reducing the oxidative strength of the atmosphere and allowing transport of pollutants to remote regions. Two conformers, cis-cis and trans-perp HOONO, are identified in the 2nuOH region by vibrational overtone initiated photodissociation spectroscopy, and the isomerization barrier from the less stable trans-perp to cis-cis HOONO is determined experimentally, statistically, and ab initio to be &sim；40 kJ/mol. This low barrier indicates that only cis-cis HOONO is atmospherically important. The complex vibrational spectroscopy of cis-cis HOONO is assigned with the aid of a simple two-dimensional OH-stretch/torsion coupling model of the planar, partially hydrogen-bound molecule. Combined with nonuniform quantum yield, this model explains the major features in the cis-cis HOONO spectrum. Its application to the fundamental region suggests an upward adjustment of the atmospherically important HOONO/HONO2 product branching ratio in the OH ＋ NO 2 association reaction. The rotational spectrum and dipole moment of cis-cis HOONO and DOONO are measured in the submillimeter region to characterize the molecular structure of HOONO and enable a quantitative atmospheric search. The overtone initiated photodissociation of PAN is studied in the 3nu CH and 4nuCH regions. No photodissociation is observed experimentally； statistical modeling is employed to estimate the importance of this process in PAN. The UV photodissociation of MHP and HMHP is studied in the 300–350 nm region and extrapolated to 400 nm to calculate total UV photolysis rates. The overtone initiated photodissociation of HMHP is studied in the 4nu OH and 5nuOH regions. The rich spectroscopy of this two-OH-chromophore molecule is assigned with the help of a one-dimensional anharmonic oscillator model on each OH stretch of three ab initio identified HMHP conformers. This modeling allows estimation of the unknown) dissociation threshold for HMHP. Lastly, an atmospheric search for HOONO, likely the most atmospherically important of the four molecules studied herein, is proposed and outlined.