Vicarious calibration methods have been developed to calibrate radiometric sensors in-flight. One such method, the irradiance-based method, requires the measurement of the diffuse-to-global (diffuse-to-total) irradiance ratio. Diffuse/global irradiance measurements may also be used to deduce atmospheric descriptors and provide a comparison with atmospheric modeling predictions. I describe the design, construction, calibration, and application of a spectral diffuse/global irradiance meter that can accomplish these objectives in this dissertation. I develop general integrating sphere theory, modeling methods, and describe the resultant computer model. The model results agreed with theory to better than 1% for a simple unbaffled integrating sphere. I applied the model to design an interior baffled integrating sphere-based cosine collector. I developed a method of tolerating the thermal expansion of Spectralon® and the collector was constructed. Measurements of the collector angular response agreed with the model predictions to better than 4% for input zenith angles from 0° to 70°. The resulting instrument is automated and collects diffuse and global irradiance from 300 nm to 1100 nm. It has a nominal 12 nm full-width at half-maximum bandpass and has a minimum sampling interval of 1 nm. I estimate the uncertainty of the measurements to be 3.2%. The largest contributor to the total uncertainty is the measurement uncertainty of the diffuse irradiance at 2.5%. The instrument was used in a field experiment. Optical depths derived from the diffuse/global irradiance measurements agreed with those derived from a solar radiometer to within 0.008. Diffuse-to-global irradiance measurements made by the instrument were compared with an independent method and found to generally agree within 6%. The measurements were consistently lower than radiative transfer modeling estimates. Top of the atmosphere relative radiances computed from the two independent diffuse-to-global irradiance data sets generally agreed to better than the 2.9% uncertainty associated with the diffuse/global irradiance meter data set. The relative radiances of the diffuse/global data set collected with the instrument were within the 4.9% uncertainty estimate of the reflectance-based method.

Powerful lasers are needed to generate artificial guide stars for astronomical adaptive optics. Continuous wave (CW) lasers yield the most efficient excitation of the D2 line in the mesopheric sodium layer. Data is presented from early systems which used commercially available CW dye lasers. Building on these results, a dye laser was designed and constructed which incorporates a sodium Faraday filter (SFF) to select and lock the laser frequency to the peak of the D2 sodium resonance. This laser was the first ring dye laser made using an intra-cavity SFF, and also the first incorporating a SFF to produce a significant amount of power in a single longitudinal mode. A major part of this thesis concerns the design and construction of the SFF. The theory of operation is developed and then used to design a SFF with a high throughput at the D2 line of sodium. The two main elements of a SFF are a sodium cell and a magnet. The design and construction of these two elements is discussed in detail. The design and construction of a wavefront sensor for the Multiple Mirror Telescope's unique geometry is presented. This wavefront sensor and a CW dye laser were used to generate the first astronomical images sharpened by an adaptive optics system incorporating a sodium laser guide star.

In order to better model the climate system, land-surface models are continuously being improved. Several studies using the Biosphere-Atmosphere Transfer Scheme (BATS) are presented. One study compares simulations with the new ten-layer soil model (TLSM) and the previous BATS soil model at global and regional scales. TLSM tends to have much higher bare soil evaporation than the previous soil model. Soil in regions with high precipitation became wetter, while soil in regions with less precipitation became much drier. Potential errors in TLSM included underpredicted runoff and high-latitude transpiration. Corrections for these errors were incorporated and tested at six points. Surface runoff is increased by extracting water from the upper three TLSM layers rather than only the top layer. Bare soil evaporation is limited to the water present in the surface soil layer. A diurnal temporal error in the downward longwave radiation forcing data did not appear to significantly affect simulated long-term or large-scale averages. However, the assumption of uniform hourly distribution of 6-hour total precipitation did impact the partitioning of precipitation into evaporation, transpiration and runoff. A new method for modeling vertical water flow in heterogeneous porous media using the water-content based form of Richards equation is described, then used with BATS/TLSM to simulate the boreal forest energy and water exchanges at a black spruce site, where a thick moss layer covers a peat/loam soil, and at an aspen site with a homogenous clay soil. The moss is treated as a type of porous media, so its unique hydraulic and thermal properties can be modeled directly. Simulated net radiation is very similar to that observed over the summer months at both sites, but latent heat is greatly overestimated and simulated sensible heat fluxes are not well correlated with the observations. Observed soil temperature profiles and soil water content profiles are well captured at the black spruce site, as is the ability of moss to keep the underlying soil layers moist and cool. Despite the successful modifications made to TLSM during this study, the overestimation of evaporation remains a problem that should be addressed before widespread use of this model occurs.

Lightning, a familiar phenomenon on Earth, may also occur at other times and locations in our solar system. It has been suggested as a mechanism for forming chondrules, millimeter-sized beads of glassy silicate found in primitive meteorites formed in the early solar system 4.5 billion years ago. It has also been detected in Voyager images of Jupiter, and there is evidence that it may occur on other planets as well, including Venus, Saturn and Neptune. The mechanism believed to produce lightning discharges on Earth, and possibly other planets, is charge production by collisions of ice particles, followed by gravitational separation of oppositely-charged large and small particles. This work examines the possibility of the occurrence of lightning discharges in the atmospheres of Jupiter and Neptune as well as in the protoplanetary nebula (PPN) of the early solar system by modeling charge separation and growth of the electric field. The model is also applied to the Earth as a test of its predictive power. It is found that the model can reproduce the correct timescale, particle charge and electric field magnitude seen in terrestrial lightning. The model also predicts lightning on Jupiter at the 3-5 bar level provided that the local water abundance is greater than the solar value. This is a much higher abundance than measured by the Galileo probe into Jupiter's atmosphere, which suggests that the water content measured by the probe does not apply to the entire planet. An application of the model to Neptune's water and NH₄SH clouds finds that lightning is unlikely in these clouds due to the large electric field required for electrical breakdown. Lightning may be possible in the overlying H₂S-NH₃ cloud provided that these substances can undergo collisional charge exchange with a magnitude at least 1% of that found in water ice. In the protoplanetary nebula, it appears that large-scale precipitation-induced lightning could not have occurred, due to the small mass density, low temperature and high electrical conductivity of the surroundings. This is a robust conclusion that does not depend sensitively on the values of the parameters involved.

This thesis examines the temporal characteristics and climatology of wintertime carbon monoxide (CO) concentrations in central Phoenix (AZ). Variations in CO concentrations on several temporal scales are explored to determine the relationship between atmospheric conditions, CO concentrations, and motor vehicle traffic levels as well as to spotlight the timing of high CO concentrations. Typical surface atmospheric conditions that are related to high and low CO mornings are revealed through compositing. Finally, a set of CO forecasting models are developed that predict 3 AM 8 hour average CO concentrations. Important results are as follows. The first three weeks of December have the most CO exceedance days. High CO concentrations are associated with anticyclonic conditions while low CO concentrations are linked to the passage of a cold front or trough. Final models had little systematic mean squared error and predictions that were within 1 ppm of the observed CO concentration.

The solar wind interaction with the non-magnetic Venerean ionospheric obstacle is unique. Ionospheric models of this interaction have primarily been in two dimensions that do not allow for changes in the orientation of the solar wind magnetic field near the obstacle. Analysis of high resolution magnetic field data from the Pioneer Venus Orbiter spacecraft has revealed field rotations that are observed to occur in conjunction with the dayside ionopause. These rotations are a result of the velocity shear at the ionopause and indicate the alignment of the magnetic field with the radial day to night flow of ionospheric plasma. A new configuration of the dayside magnetic field draping has been derived from these results. In addition, a new current system to account for this changing field orientation has been determined and is discussed in relation to current systems derived from previous models. These new aspects of the dayside solar wind interaction at Venus can be applied to other similar solar system objects. Assuming Mars also represents a non-magnetic obstacle to the flow, as past experimental observations indicate, the field diagnostics discovered here make it possible to probe the structure of the Martian ionosphere using magnetometer data in the absence of ion mass spectrometer data. These results will play a major role in predictive modeling and data analysis for future Mars missions.

Lightning on Venus has been suggested by many researchers. The evidence for this lightning has been claimed to be impulsive electric field signals which have been detected by a number of spacecraft. However, others have proposed that the observed signals are a result of local ionospheric plasma instabilities and do not originate in the lower atmosphere. An investigation of 100 Hz electric field signals detected within the ionosphere of Venus has been conducted. The study encompassed both previously published 100 Hz signals which have been identified as being a result of lightning in the lower atmosphere and data which was newly selected for this research. It is shown that the 100 Hz signals result most often from the lower hybrid plasma wave mode. The remaining signals are from other plasma instabilities due to magnetic field and/or ion density gradients.

Solar wind interactions with planets that possess neither an intrinsic magnetic field nor a significant ionosphere have not been well studied. We have constructed a model to simulate the interaction between a hot magnetized plasma and a planet containing only a neutral atmosphere. Examination of the boundary conditions that yield a physically valid solution shows that the interaction is similar to the solar wind interaction with Venus. We show that most (97%) of the incident flow is deflected around the atmosphere, and the small fraction that enters interacts in such a way as to transfer the flowing momentum through the neutral atmosphere to the planetary body. This demonstrates that the true barrier to a flowing plasma, such as the solar wind, is neither its ionosphere nor its intrinsic magnetic field, but rather the planetary body itself.

The application of diode-laser-pumped tunable IR sources to trace gas detection in air is discussed. The design and technology issues of CW tunable mid-infrared difference-frequency generation are addressed. Feasibility experiments are reported in which the detection of CH$\sb4$, and CO was performed at low pressure and in air using two laser sources near 3.2 $\mu$m, and 4.7 $\mu$m, respectively. They were based on difference-frequency mixing in AgGaS$\sb2$ at room temperature. Pump sources used were a diode-pumped Nd:YAG laser at 1064 nm, a laser diode at 693 nm, and a tunable fiber-coupled Ti:Sapphire laser near 795 nm, and 813 nm. Detection limits of 2.4 ppb*m/$\rm\sqrt{Hz}$ for CO, and 9.0 ppb*m/$\rm\sqrt{Hz}$ for CH$\sb4$ in air are estimated for 0.1 $\mu$W of IR probe power based upon the performance of the sources and detector.

The Voyager 2 encounter with Neptune and Triton in August of 1989 provided clues to an intriguing problem. Instruments onboard the spacecraft showed a large ionosphere at Triton. Subsequent studies have tried to explain the production of such high levels of ionization but have ignored the possible plasma dynamics originating from the interaction between Neptune's magnetosphere and Triton. This study applies knowledge gained from studying the solar wind-Venus interaction to this case. In doing so we find that observations made by Voyager 2 can be explained by downward convection of magnetospheric plasma into Triton's atmosphere. Furthermore, we find that the flowing momentum is transferred to the moon just below the exobase, calculated here to be approximately 750 km. From this point down the atmosphere is not in hydrostatic equilibrium, and cannot be until below the ionization peak. Finally we show that when the momentum gets transferred to the moon the flow must shut off. This is accomplished when both the convective velocity and magnetic field go to zero. By showing the magnetic field vanishes at an altitude of roughly 650 km, we conclude the accepted mechanism by which the ionosphere is produced to be invalid. This mechanism was identified early-on to be impact ionization from hot, or superthermal, electrons originating in Neptune's magnetosphere. These precipitating hot electrons are thus shown to operate independently of the magnetic field below the exobase. This is a result not previously discovered, and one which implies that the plasma interaction between Neptune's magnetosphere and Triton cannot be ignored.