<p> Heat stress is a global issue that crosses socioeconomic status. Heat stress leads to reduced worker capacity on seasonal scales, and weekly to sub-daily timescales, incapacitation, morbidity, and mortality. This dissertation focuses on 2 distinct parts: quantification methods of heat stress, and heat stress applications.</p><p> <b>Quantification methods of heat stress:</b> Chapters 1&ndash;3 focus on historical analysis of heat stress. Chapter 1 is a detailed assessment of previous work in heat stress&mdash;methods, history, and future research out- look. Chapter 2 focuses on the implementation and quantification of a battery of heat stress metrics within the global circulation model framework. The ultimate outcome is a Fortran module, the HumanIndexMod [1], that may be run independently on individual datasets, or used with the Community Earth System Model 1, Community Land Model Version 5 (released February 2018 w/HumanIndexMod). Chapter 3 is an analysis of a battery of heat stress metrics with the focus on showing their differences in global circulation models, and thermodynamic predictability and scalability.</p><p> <b>Heat stress applications:</b> Chapters 4 and 5 focus on applications for physical impact modeling and economic outcomes. Chapter 4 quantifies labor impacts from heat stress due to the covariance or temperature, humidity, and radiation. My predictions of labor productivity losses from heat stress are amenable to Integrated Assessment Modeling. Chapter 5 is a preliminary economic impacts analysis&ndash;a 1^st order sensitivity perturbation study for labor impacts&ndash;which will guide a flagship application for the Purdue University Big Idea Project, GLASS: Global to Local Analysis of Systems Sustainability. My labor productivity losses from heat stress will become a boundary condition for a series of sensitivity assessments intended to inform the policy making process to help achieve the United Nations Sustainability Development Goals.</p><p>

<p> The connection between ionospheric conductivity and the dynamics of the magnetosphere was investigated, using several methods to change the ionospheric conductivity and then study the resultant changes to the magnetosphere. Computer simulations of the Earth's geospace environment were utilized using OpenGGCM coupled with an ionosphere model CTIM and a ring current model RCM. </p><p> Three methods were used to modify ionospheric conductivity. The incoming particle precipitation was modified by several orders of magnitude &alpha; = .01, .1, 1, 10, the ionospheric conductivity was increased or decreased by factors &beta; = .25, .5, 1, 2, and 4, and for the last method differing values of <i>F</i>_10.7, 70, 110, 150, 200, and 250 were used. Each of the methods is different because <i>F</i>_10.7 mostly affects the dayside, while precipitation mostly affects the nightside, then using the &beta; changes the conductivity over the whole ionosphere. This gives a good range for studying the effects of ionospheric conductivity on the magnetosphere. </p><p> The magnetospheric dynamics studied are: the dayside magnetopause location, the reconnection rate of the Earth's magnetosphere, X-line formation in the magnetotail, and substorm dynamics, both the frequency and magnitude of substorm occurrence. </p><p> To understand the effect of particle precipitation on conductivity two events were simulated, a calm period on 4 May 2005 and a strong storm period on 17 March 2013. Scaling the precipitation energy flux by several orders of magnitude, conductivities in the auroral oval were influenced which, in turn, influence the cross polar cap potentials. With the change in conductance, magnetospheric convection is enhanced or reduced, and the location of the subsolar distance of the magnetopause can change by up to one <i>R_E</i>. The investigation of the reconnection rate for the varying precipitation simulations using the Hesse-Forbes-Bern method shows that particle precipitation affects the magnetic reconnection rate in these two events. The most notable differences, up to 40\%, occur on short time scales, that is, hours. A relation for longer time scales (tens of hours) between precipitation and reconnection for these two events is more difficult to ascertain. Differences in cross polar cap potential (CPCP) and reconnection rate (R) can be explained by viscous interactions and polar cap saturation. When precipitation was decreased, polar conductance was decreased, viscous interactions are stronger, and CPCP is higher than R. For high precipitation, high conductance cases the polar cap is in the saturation regime and CPCP is lower than R. Hemispheric asymmetries were found in the cross polar cap potential and in the calculated reconnection rate derived from the Northern and Southern Hemispheres. The majority of this research has already been published in the Journal of Geophysical Research: Space physics, "Particle Precipitation Effects on Convection and the Magnetic Reconnection Rate in Earth's Magnetosphere" https://doi.org/10.1002/2017JA024030. </p><p> For the whole ionospheric conductivity study, different values of &beta; = .25, .5, 1, 2, 4 were used to modify the ionospheric conductivity after it had been calculated by the ionosphere model. A moderate storm period, 16 May 2011 was simulated. Many of the same conclusions found in the precipitation study were found in this study as well, such as, CPCP decreasing as conductivity increases, the point at which the polar cap saturates decreases with increasing conductivity, and reconnection rates change on short time scales, but the overall average rate remains very similar. The incoming precipitation was used to identify auroral brightening that is linked with substorms. The criteria for auroral brightenings used in this study is where the maximum precipitation increased by at least 1 <i>mW/m</i>² within 20 minutes. The criteria for substorms is that the maximum precipitation increases by 80\% within 20 minutes. Identifying all the auroral brightenings and substorms showed that as conductivity increased the maximum amount of precipitation decreased, and also the number and frequency of both the substorms and auroral brightenings decreased. The occurrence of extended X-lines in the magnetotail was analyzed, where if an earthward flow of greater than 50 km/s extended for greater than 10 <i>R_e</i> in <i>Y_GSE</i> was classified as an extended X-line. This is not to be confused with a bursty bulk flow or dipolarization front, which happen from reconnection but usually do not have a large extent in <i>Y_GSE</i>. Identifying extended X-lines in this manner showed a similar trend that as conductivity increased the number of extended X-lines decreased, and while there was not much of an indication if the size or location is affected much, the amount of time the simulation had extended X-lines present decreased. </p><p> For the <i>F</i>_10.7 study, using values of 70, 110, 150, 200, and 250, the ionospheric conductivity was influenced mostly on the dayside. (Abstract shortened by ProQuest.) </p><p>

<p> Satellite cloud remote sensing provides us the opportunity to study the spatial and temporal distributions of marine boundary layer clouds, as well as their connections with environments on a global scale. However, cloud remote sensing is not without difficulties; retrievals require numerous simplifying assumptions, placing limits on our understanding of cloud processes. Passive remote sensing retrievals often assume that clouds are homogeneous slabs, when in reality, these clouds often have complex inhomogeneous vertical and horizontal structures. Enhancing our understanding of how cloud inhomogeneity influences passive cloud remote sensing requires comparison between cloud retrievals and the underlying cloud properties. In observational data-sets this can become problematic, as it is difficult to compare satellite and airborne measurements because they have both different observed spatial scales and sensitivities to cloud properties. To avoid these complications, this work is based on a satellite retrieval simulator &ndash; a Large-Eddy Simulation (LES) cloud model coupled to radiative transfer and retrieval algorithms. The LES-satellite simulator can be used to study the source of retrieval biases. It provides the underlying realistic cloud structure as a reference, informing conclusions about its impact on various cloud retrieval methods. In the first step we focus on cloud vertical profile, finding that the selection of appropriate vertical profile assumptions for the retrieval of cloud liquid water path. Confirming previous studies, drizzle and cloud top entrainment of dry air are identified as physical features that bias liquid water path retrievals away from adiabatic and toward homogeneous profile assumptions. The mean bias induced by drizzle-influenced profiles was shown to be on the order of 5&ndash;10 grams per meter squared. In contrast, the influence of cloud top entrainment was found to be smaller by about a factor of 2. A theoretical framework is also developed to explain variability in LWP retrievals by introducing modifications to the adiabatic effective radius profile. The second step focuses on horizontal inhomogeneity and exploring a comparison of both the bispectral and polarimetric cloud retrieval techniques. Using the satellite retrieval simulator we are able to verify that at high spatial resolution (50 meters) the bispectral and polarimetric retrievals are indeed highly correlated with one another. The small differences at high spatial resolution can be attributed to different sensitivity limitations of the two retrievals. In contrast, a systematic difference between the two effective radius retrievals emerges at coarser resolution. This bias largely stems from differences related to sensitivity of the two retrievals to unresolved inhomogeneities in effective variance and optical thickness. The influence of coarse angular resolution is found to increase uncertainty in the polarimetric effective radius retrieval, but generally maintains a constant mean value. The third study focuses on 3-D radiative effects influencing both total and polarized reflectances and retrievals. Comparisons between the 1-D and 3-D reflectances are made in order to study horizontal photon transfer and radiative smoothing. We find noticeable differences between the total and polarized reflectance 3-D effects, with radiative smoothing and roughening occurring at different scales as well as viewing geometry dependence. Despite these apparently strong 3-D effects on polarized reflectances, the polarimetric retrieval is robust to the influence of 3-D effects &ndash; with only sub-micron biases in the retrieval of effective radius.</p><p>

<p> The study described in this thesis aims to assess the effects of wind-generated noise on potential infrasound measurements on future Mars missions. Infrasonic sensing on Mars is being considered as a means to probe the long-scale atmospheric dynamics, thermal balance, and also to infer bolide impact statistics. In this study, a preliminary framework for predicting the principal wind noise mechanisms to the signal detected by a sensor placed inside a hemispherical porous dome on the Martian surface is developed. The method involves calculating the pressure power density spectra in the infrasonic range generated by turbulent interactions and filtered by dome shaped filters of varying porosities. Knowing the overall noise power spectrum will allow it to be subtracted from raw signals of interest and aid in the development of infrasound sensors for the Martian environment. In order to make these power spectral predictions, the study utilizes the Martian Climate Database (MCD) global circulation model, developed by Laboratoire de Meteorologie Dynamique in Paris, France. Velocity profiles are generated and used in semi empirical functions generated by von K&aacute;rm&aacute;n along with equations for describing the physical turbulent interactions. With these, turbulent interactions in the free atmosphere above the Martian surface are described. For interactions of turbulence with the porous filter, semi-empirical formulations are adapted to the Martian parameters generated by the MCD and plotted alongside contributions in the free atmosphere outside and inside the dome to obtain the total wind noise contribution from turbulence. In conclusion, the plots of power spectral densities versus frequency are analyzed to determine what porosity filter would provide the best wind-noise suppression when measured at the center the dome. The study shows that 55% (0.02 to 5 Hz) and 80% (6 to 20 Hz) porosities prove to be the better of the five porosities tested. </p><p>

<p> This study gained novel insights into mechanistic interactions of dust and smoke particles with large-scale climate dynamics. This study revealed that the variability Saharan dust radiative properties is significantly linked to high-frequency atmospheric wave activity across the tropical Atlantic storm tracks, while the variability of smoke particles from the South African biomass burning is attributed by low-frequency oscillations of baroclinic instability of the region. </p><p> We proposed that the impacts of Saharan Air Layer (SAL) on large-scale climate dynamics mainly occur through coupling of dust radiative forcing with eddy energetics of the African easterly jet-African easterly waves (AEJ-AEWs) systems. This study quantified the thermal/mechanical impacts of oceanic SAL on activity of the AEWs and the regional feedback of eddies onto the mean-circulations from a climatological point of view. We found that both upstream and downstream developments of eddy energy are affected by oceanic SAL radiative forcing. It is suggested that dust radiative forcing has the capability to affect the transient changes in baroclinic instability of the jet-wave system through eddy available potential energy, and contribute in exchange of kinetic energy between the AEWs and AEJ through baroclinic and barotropic conversions.</p><p> This study discussed that Saharan dust radiative properties have both constructive and destructive effects on behaviors of the AEWs, which depend on structure of the waves at different time-scale: the eddy kinetic energy (EKE) of the 2&mdash;6-day ultrahigh-frequency waves are amplified in average 1-day after enhancing of dust radiative forcing, while the EKE of the 6&mdash;11-day intermediate-frequency waves weakens during dust storm events. In addition, over the western African monsoon (WAM) region and the entrance of the tropical Atlantic storm track, the 2&mdash;6-day filtered AEWs become more barotropic during oceanic SAL outbreaks. The anomalous changes in meridional and quadruple momentum fluxes of 2&mdash;6-day filtered AEWs, associated with enhanced dust in the oceanic SAL, tend to an easterly feedback onto the southern edge of the mean-AEJ. However, at the middle- to exit region of the southern storm track, the anomalous convergent momentum fluxes of 2&mdash;6-day AEWs, associated with dust outbreak, tends to increase the regional baroclinic instability through the 3 main local energy packets, which may initiate a higher chance of hurricane activity.</p><p> Applying ensemble of large NASA satellite observations data sets, such as MODIS, SeaWiFS and TRMM as well as GOCART aerosol model and MERRA reanalysis indicates that the suggested results are consistent regardless of the selected data sets. Overall, we proposed that the regional radiative properties of aerosols and thermal/mechanical activity of wave-jet systems are dynamically coupled and it is not suggested to consider either as a response to one another. </p><p>

The simulation of the atmospheric turbulence has wide applications in science and engineering. There are a variety of modelling techniques for synthesizing a wind speed time series available today. To decide which model to use one has to know the characteristics of the simulation technique. In this dissertation, alternative approaches for synthetically generating a wind speed time series are discussed. These approaches include: (1) the use of independent values from a specific probability distribution; (2) the use of an algorithm based on the statistical behavior of a one step Markov chain; (3) the use of an algorithm based on the behavior of a transition probability matrix that describes the next wind speed value statistically as a function of the current wind speed value and the previous wind speed value; (4) the use of Box-Jenkins model; (5) the use of the Shinozuka algorithm; (6) the use of an embedded Markov chain; and (7) the use of the fractal concept. The ability of each approach to capture the statistical properties of the desired wind speed time series is discussed. Wind speed collected at Windsor, Massachusetts and at Altamont, California are used as target wind speed values. Each model will be used to generate a synthetic wind speed for each site to compare with the real wind speed. The performance of each model will be decided on by the statistical similarity of the synthetic wind speed to the real wind speed. The criteria of the statistical similarity include the mean and the variance of the wind speed values, the probability distribution of the wind speed values, the power spectrum of the wind speed values and the autocorrelation function of the wind speed values. One of the applications of the wind speed simulation is to fill in a missing segment of a wind speed time series. In this context the missing segment of the wind speed at Cuttyhunk island is simulated and filled in for the study of a wind/diesel energy conversion system.