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This dissertation presents the design and operation of a high-resolution frequency-modulated continuous-wave (FM-CW) radar system to study the structure and dynamics of clear-air turbulence in the atmospheric boundary layer (ABL). This sensitive radar can image the vertical structure of the ABL with both high spatial and temporal resolutions, and provide both qualitative information about the morphology of clear-air structures and quantitative information on the intensity of fluctuations in refractive-index of air. The principles of operation and the hardware and data acquisition characteristics of the radar are described in the dissertation. In October 1999, the radar participated in the Cooperative Atmosphere-Surface Exchange Study (CASES'99) Experiment to characterize the temporal structure and evolution of the boundary-layer features in both convective and stable conditions. The observed structures include clear-air convection, boundary layer evolution, gravity waves, Kelvin-Helmholtz instabilities, stably stratified layers, and clear-air turbulence. Many of the S-band radar images also show high-reflectivity returns from Rayleigh scatterers such as insects. An adaptive median filtering technique based on local statistics has, therefore, been developed to discriminate between Bragg and Rayleigh scattering in clear-air radar observations. The filter is tested on radar observations of clear air convection with comparison to two commonly used image processing techniques. The dissertation also examines the statistical mean of the radar-measured [special characters omitted] for clear-air convection, and compares it with the theoretical predictions. The study also shows that the inversion height, local thickness of the inversion layer, and the height of the elevated atmospheric layers can be estimated from the radar reflectivity measurements. In addition, comparisons to the radiosonde-based height estimates are made. To examine the temporal and spatial structure of [special characters omitted], the dissertation presents two case studies with the measurements of remote (the FM-CW radar and Doppler lidar) and in-situ (research aircraft, kite, and radiosonde) sensors from the stable nighttime boundary layer. It also presents a unique observation of evolution of the convective and nocturnal boundary layers by the S-band radar, and provides description of the observed boundary layer characteristics with the aid of in-situ measurements by the 55m instrumented tower and radiosonde.

This dissertation analyzes the retrieval of water vapor profiles via microwave radiometry; in particular it determines the information content of spectral data and identifies optimal measurement frequencies using an information content technique. The vertical resolution and estimate variance of water vapor profiles derived from the linear inversion of atmospheric data is examined and the effects of measurement noise on these quantities is considered. The Microwave Remote Sensing Laboratory at the University of Massachusetts has developed a unique K-Band Spectral Radiometer (KSR) system that simultaneously monitors eighteen frequencies near the 22.235 GHz water vapor absorption line and is designed to retrieve atmospheric water vapor density profiles by inverting spectral radiance measurements. This system is unique in its measurement speed and breadth. The dissertation discusses calibration techniques, system parameters, and the derivation of a statistical estimation algorithm is that is applied to KSR measurements taken during a field experiment in Lamont, Oklahoma. The resulting water vapor profiles are presented, along with a comparison of in-situ and independent observations.

This dissertation describes the design, fabrication and deployment of the Compact Microwave Radiometer for Humidity profiling (CMR-H). The CMR-H is a new and innovative spectrometer radiometer that is based on monolithic microwave and millimeter-wave integrated circuit (MMIC) technology and is designed for tropospheric water vapor profiling. The CMR-H simultaneously measures microwave emission at four optimally-selected frequency channels near the 22.235 GHz water vapor absorption line, constituting a new set of frequencies for the retrieval of the water vapor profile. State-of-the-art water vapor radiometers either measure at additional channels with redundant information or perform multi-frequency measurements sequentially. The fabrication of the CMR-H demonstrates the capability of MMIC technology to reduce substantially the operational power consumption and size of the RF and IF sections. Those sections comprise much of the mass and volume of current microwave receivers for remote sensing, except in the case of large antennas. The use of the compact box-horn array antenna in the CMR-H demonstrates its capability to reduce the mass and volume of microwave radiometers, while maintaining similar performance to that of commonly-used, bulky horn antennas. Due to its low mass, low volume, low power consumption, fabrication complexity and cost, the CMR-H represents a technological improvement in the design of microwave radiometers for atmospheric water vapor observations. The field test and validation of the CMR-H described in this work focuses on comparisons of measurements during two field experiments from the CMR-H and a state-of-the-art microwave radiometer, which measures only in a volume subtended by the zenith-pointing antenna's beam pattern. In contrast, the CMR-H is designed to perform volumetric scans and to function correctly as a node in a network of radiometers. Mass production of radiometers based on the CMR-H design is expected to enable the implementation of a dense network of radiometers designed to perform measurements of the 3-D water vapor field, with the potential to improve weather forecasting, particularly the location and timing of the initiation of intense convective activity responsible for potentially damaging winds, rain, hail and lightning.

When an optical wave propagates through atmosphere, the wave experiences amplitude, phase, and angle-of-arrival (AOA) fluctuations which are mainly caused by the refractive-index fluctuations of the atmosphere. Thus, the wave fluctuations carry characteristics of the atmosphere. In this dissertation, the AOA fluctuations are studied theoretically and experimentally. For the theoretical part, closed-form solutions of the AOA fluctuations for plane and spherical waves observed by a receiver with a finite aperture were developed. It was assumed that the waves propagate through homogeneous and isotropic media and that the Rytov approximation is valid. The existing closed-form solutions of the AOA fluctuations for the waves are valid only for the cases that the aperture size of the receiver is much larger or much smaller than the Fresnel length. The closed-form solutions developed in this dissertation, however, are valid for all ratios between the aperture diameter and the Fresnel length. The closed-form solutions were compared with the numerical solutions and the accuracy of the closed-form solutions is less than 0.2%. For the experimental part, remote sensing of wind speed transverse to a propagation path using the frequency spectra of the AOA fluctuations was performed with a telescope and a CCD camera. The knee frequency, the intersection of the -2/3 and -8/3 power laws of the spectrum, is a function of wind speed and an effective baseline. If the knee frequency and the effective baseline are known, the transverse wind speed can be retrieved, and if the knee frequency and the transverse wind speed are known, the effective baseline can be estimated. From the measured knee frequency of the spectra of the AOA fluctuations and the aperture size of the telescope as initial guess for the effective baseline, the path-averaged transverse wind speed was retrieved. The effective baseline was calibrated based on wind speed measured by a anemometer. The rms difference between the path-averaged calibrated wind speed retrieved from the frequency spectra of the AOA fluctuations with 30 s of estimation time and the 30 s time-averaged transverse wind speed measured by the anemometer was 11 cm/s -1, while the wind speed varied between 0 and 80cm/s-1.

No description available.

Spectroscopic measurements in the infrared have proven to be a valuable source of information about the Jovian atmosphere. However, numerous questions remain, many of which will be addressed by the Galileo μission, due to arrive at Jupiter in December, 1995. One of the instruments on Galileo is the Near-Infrared Mapping Spectrometer (NIMS), which will measure temperature structure, cheμical composition, and cloud properties. The objective of the work described in this thesis was to investigate the transmittance properties of the Jovian atmosphere and, in particular, to obtain transmittance functions of CH₄ for future use in the planning and interpretation of NIMS measurements. This thesis begins with a review of our current understanding of the Jovian atmosphere (Chapter 1), and a description of the Galileo μission and the design and objectives of NIMS (Chapter 2). It is then shown (Chapter 3) that absorption bands of CH₄ doμinate the nearinfrared spectrum of Jupiter, but that line data for CH₄ are currently inadequate over much of the NIMS spectral range (0.7-5.2 /μi). For the purposes of NIMS, which has a low resolution of 0.25 /μi, the spectrum of CH₄ can be characterised using band models of transmittance as a function of temperature, pressure, and abundance. The theory of band modelling is presented, and previous band-modelling studies of CH₄ are reviewed and are also shown to be inadequate for NIMS (Chapter 4). An experimental investigation was therefore undertaken to record CH₄ spectra under Jovian conditions of low temperature, large abundance, and H₂-broadening. The experimental resources used to obtain these spectra are described (Chapter 5), the generation of the transmittance spectra is discussed, and their quality is assessed (Chapter 6). The range of frequencies and laboratory conditions covered by these spectra (listed in Appendix A) makes them one of the most comprehensive data sets of this kind yet published. These spectra were subsequently used to derive transmittance functions for CH₄ (Chapter 7). A variety of models were fitted to the self-broadened CH₄ spectra, and the Goody and Malkmus random band models, using the Voigt lineshape, are shown to provide the best fits. These two models were then fitted to the combined set of self- and H₂-broadened CH₄ spectra. The parameters fitted with the Goody-Voigt model are included in this thesis (Appendices B and C). Finally, the application of these new band model fits to the problem of Jovian remote sounding is addressed (Chapter 8). This includes an assessment of the reliability of extrapolation to Jovian conditions, a calculation of the level in the Jovian atmosphere that will be sounded by observations of CH₄ absorption, and a calculation of how the uncertainties in the fitted band model will affect the retrieval of atmospheric parameters from NIMS spectra. This thesis concludes with a detailed summary, and with suggestions for future investigations which will help to maximise the return of information from NIMS.

Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Bibliography: leaves 305-312. / by William Henry Ledsham, Jr. / Ph.D.

This study had as objective to show the importance of the spectral characteristics obtained by the physical properties of clouds measured by the METEOSAT geostationary satellite that helps on the understanding and prediction of severe storms. The study area was Brazil s southeastern because this region is located in a transition range between the mid-latitude temperate climate and the low latitudes warm climate and, therefore, becomes an area that has influence of various meteorological phenomena. With the strong topography and the proximity to the Atlantic Ocean, is a severe storms, strong winds and continuous rainfall favorable zone. It were used MSg datanot only by the images been captured from 15 in 15 minutes, but also because the SEVIRI radiometer on board of the European satellite has 12 multispectral channels that generate twenty times more information than the previous generation radiometers of the same. Were generated qualitative information of the atmospheric events in RGB color compositions, spectral response analysis and differences in the water vapor multispectral channels. The obtained results indicated that the RGB color composition (WV6.2μm - WV7.3μm; IR3.9μm - IR10.8μm; NIR1.6μm - VIS0.6μm) characterizes in a satisfactory way the convection in thunderstorms, showing when the system is in dissipation, stabilization or increasing, but is indicated only for storms occurring during the day and when analyzed the 3 RGB compositions (standard for air mass and convection) generate more information than analyzing only 1 of them. For the first case study, the values of the channel difference of the water vapor that were indicated as critical values with a trend to storm formation were of 4 to 13 ºC and for the second study case were of 8 to 13 °C. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho teve por objetivo mostrar a importância que as características espectrais obtidas por meio das propriedades físicas das nuvens medidas pelos satélites geoestacionários METEOSAT que auxilia a previsão e compreensão de tempestades severas. A região de estudo foi o sudeste brasileiro por essa região encontrar-se em uma faixa de transição entre o clima temperado das latitudes médias e o clima quente das latitudes baixas e, por isso, se torna uma área que tem influência de vários fenômenos meteorológicos. Com a topografia acentuada e a proximidade com o Oceano Atlântico, é uma zona propicia a tempestades severas, vendavais e chuvas contínuas. Foram utilizados os dados do MSG não apenas pelas imagens serem captadas de 15 em 15 minutos, mas também, porque o radiômetro SEVIRI a bordo desse satélite europeu possui 12 canais multiespectrais que geram vinte vezes mais informações do que os radiômetros da geração anterior do mesmo. Foram geradas informações qualitativas dos eventos atmosféricos nas composições coloridas RGB, análise da resposta espectral e diferenças dos canais multiespectrais de vapor de água. Os resultados obtidos indicaram que a composição colorida RGB (WV6.2µm WV7.3µm; IR3.9µm IR10.8µm; NIR1.6µm VIS0.6µm) caracteriza de maneira satisfatória a convecção em tempestades, mostrando quando o sistema está-se dissipando, estabilizado ou intensificando, porém é indicada apenas para as tempestades que ocorrem durante o dia e quando analisada as 3 composições RGB (padrão, para massas de ar e convecção) geram mais informações do que analisando apenas 1 delas. Para o 1° estudo de caso os valores da diferença de canais do vapor de água que foram indicados como valores críticos propícios a formação de tempestades foram de 4 a 13°C e para o 2° estudo de caso foram de 8 a 13°C.

Biogenic isoprene plays an important role in tropospheric chemistry. We use HCHO column measurements by the Global Ozone Monitoring Experiment (GOME) to constrain isoprene emissions. Using the global Goddrad Earth Observing SystemChemistry (GEOS-Chem) as the forward model, a Bayesian inversion of GOME HCHO observations from September 1996 to August 1997 is conducted. Column contributions to HCHO from 12 sources including 10 terrestrial ecosystem groups, biomass burning, and industry are considered and inverted for 8 geographical regions globally. The a posteriori solution reduces the model biases for all regions, and estimates the annual global isoprene emissions of 566 Tg C yr-1, ~50% larger than the a priori estimate. Compared to the Global Emissions Inventory Activity (GEIA) inventory (~500 Tg C yr-1), the a posteriori isoprene emissions are generally higher at mid latitudes and lower in the tropics. This increase of global isoprene emissions significantly affects tropospheric chemistry, decreasing the global mean OH concentration by 10.8% to 0.95106 molecules/cm3. The atmospheric lifetime of CH3CCl3 increases from 5.2 to 5.7 years. Positive matrix factorization (PMF), an advanced method for source apportionment, is applied to TRAnsport of Chemical Evolution over the Pacific (TRACE-P) measurements and it is found that cyanogenesis in plants over Asia is likely an important emission process for CH3COCH3 and HCN. This approach also is applied to estimate source contributions to the tropospheric ozone (O3) with Tropospheric Ozone Production about the Spring Equinox (TOPSE) and TRACE-P measurements. The corresponding GEOS-Chem simulations are applied to the same factor-projected space in order to evaluate the model simulations. Intercontinental transport of pollutants is most responsible for increasing trend of springtime O3, while stratospheric influence is the largest contributions to troposperic O3 variability at northern middle and high latitudes. On the other hand, the overall tropospheric contributions to O3 variability are more important at northern low latitudes by long-range transport, biomass burning, and industry/urban emissions. In general, the simulated O3 variabilities are comparable with those of observations. However, the model underestimates the trends of and the contributions to O3 variability by long-range transport of O3 and its precursors at northern middle and high latitudes.