This report is a tutorial on the effects of atmospheric turbulence upon systems which rely upon the propagation of LASER beams. In addition to providing a simplified presentation of turbulence theory and optical effects, it describes the state of the art of the new technique of radiosonde estimation of index of refraction fluctuations. Suggestions are given for future research which will help to answer current Air Force needs. The feasibility of some laser systems will depend upon the value of r0, the coherence length (which is related to “C2n” which in turn is related to the degree of turbulence). At present, the statistics of “r0” are inadequate.
This book collects most of the talks and poster presentations presented at the Optical Turbulence OCo Astronomy meets Meteorology international conference held on 15OCo18 September, 2008 at Nymphes Bay, Alghero, Sardinia, Italy. The meeting aimed to deal with one of the major causes of wavefront perturbations limiting the astronomical high-angular-resolution observations from the ground. The uniqueness of this meeting has been the effort to attack this topic in a synergic and multidisciplinary approach promoting constructive discussions between the actors of this science OCo the astronomers, meteorologists, physicists of the atmosphere and the experts in adaptive optics and interferometry techniques whose main goal is to correct, in real-time, the wavefront perturbations induced by atmospheric turbulence to restore at the telescope foci the best available image quality. Sample Chapter(s). Chapter 1: Optical Turbulence in High Angular Resolution Techniques in Astronomy (494 KB). Contents: Optical Turbulence in High Angular Resolution Techniques in Astronomy (J M Beckers); Optical Turbulence Profiles at CTIO from a 12-Element Lunar Scintillometer (P Hickson et al.); High Resolution SLODAR Measurements on Mauna Kea (T Butterley et al.); How We Can Understand the Antarctic Atmospheric? (J W V Storey et al.); The Paranal Surface Layar (J Melnick et al.); Introduction to Data Assimilation in Meteorology (P Brousseau OC L Auger); The Mauna Kea Weather Center: A Case for Custom Seeing Forecasts (T Cherubini et al.); Dealing with Turbulence: MCAO Experience and Beyond (R Ragazzoni et al.); Future-Look Science Operations for the LBT (R F Green); Surface Layer SLODAR (J Osborn et al.); and other papers. Readership: Advanced undergraduates and graduate students, and physicists working in the field of astronomy.
This book collects most of the talks and poster presentations presented at the 'Optical Turbulence — Astronomy meets Meteorology' international conference held on 15-18 September, 2008 at Nymphes Bay, Alghero, Sardinia, Italy. The meeting aimed to deal with one of the major causes of wavefront perturbations limiting the astronomical high-angular-resolution observations from the ground. The uniqueness of this meeting has been the effort to attack this topic in a synergic and multidisciplinary approach promoting constructive discussions between the actors of this science — the astronomers, meteorologists, physicists of the atmosphere and the experts in adaptive optics and interferometry techniques whose main goal is to correct, in real-time, the wavefront perturbations induced by atmospheric turbulence to restore at the telescope foci the best available image quality./a
Since publication of the first edition of this text in 1998, there have been several new, important developments in the theory of beam wave propagation through a random medium, which have been incorporated into this second edition. Also new to this edition are models for the scintillation index under moderate-to-strong irradiance fluctuations; models for aperture averaging based on ABCD ray matrices; beam wander and its effects on scintillation; theory of partial coherence of the source; models of rough targets for ladar applications; phase fluctuations; analysis of other beam shapes; plus expanded analysis of free-space optical communication systems and imaging systems.
Anyone who has experienced turbulence in flight knows that it is usually not pleasant, and may wonder why this is so difficult to avoid. The book includes papers by various aviation turbulence researchers and provides background into the nature and causes of atmospheric turbulence that affect aircraft motion, and contains surveys of the latest techniques for remote and in situ sensing and forecasting of the turbulence phenomenon. It provides updates on the state-of-the-art research since earlier studies in the 1960s on clear-air turbulence, explains recent new understanding into turbulence generation by thunderstorms, and summarizes future challenges in turbulence prediction and avoidance.
Turbulence-the randomly disordered movement of volumes of air of widely varying size-is one of the characteristic features of atmospheric air flows; its investigation is essential for the solution of several theoretical and practical problems. Until recently, owing to experimental difficulties, research on turbu lence was confmed mainly to the lower half of the troposphere. Theoretical investigations have consequently been based on these data. The rapid development of high-altitude aviation and cases of aircraft encoun tering hazardous turbulence led to a sharp intensification of research on turbu lence in the atmosphere up to 10-12 km, and subsequently at greater altitudes. Such research was confined initially to the characterization of the frequency of occurrence of gusts of different speeds, their relation to altitude, geographical conditions, time of day and year, and so on. At the end of the fifties, when the required measuring equipment and experimental techniques had been developed, it became possible to investigate the complete statistical characteristics of turbu lence: the spectral densities of the velocity fluctuations of air flows, structure functions, etc. These data stimulated the further development of theory related to the specific conditions of the free atmosphere.
This monograph is devoted to urgent questions of the theory and applications of the Monte Carlo method for solving problems of atmospheric optics and hydrooptics. The importance of these problems has grown because of the increas ing need to interpret optical observations, and to estimate radiative balance precisely for weather forecasting. Inhomogeneity and sphericity of the atmos phere, absorption in atmospheric layers, multiple scattering and polarization of light, all create difficulties in solving these problems by traditional methods of computational mathematics. Particular difficulty arises when one must solve nonstationary problems of the theory of transfer of narrow beams that are connected with the estimation of spatial location and time characteristics of the radiation field. The most universal method for solving those problems is the Monte Carlo method, which is a numerical simulation of the radiative-transfer process. This process can be regarded as a Markov chain of photon collisions in a medium, which result in scattering or absorption. The Monte Carlo tech nique consists in computational simulation of that chain and in constructing statistical estimates of the desired functionals. The authors of this book have contributed to the development of mathemati cal methods of simulation and to the interpretation of optical observations. A series of general method using Monte Carlo techniques has been developed. The present book includes theories and algorithms of simulation. Numerical results corroborate the possibilities and give an impressive prospect of the applications of Monte Carlo methods.
According to the United Nations, three out of five people will be living in cities worldwide by the year 2030. The United States continues to experience urbanization with its vast urban corridors on the east and west coasts. Although urban weather is driven by large synoptic and meso-scale features, weather events unique to the urban environment arise from the characteristics of the typical urban setting, such as large areas covered by buildings of a variety of heights; paved streets and parking areas; means to supply electricity, natural gas, water, and raw materials; and generation of waste heat and materials. Urban Meteorology: Forecasting, Monitoring, and Meeting Users' Needs is based largely on the information provided at a Board on Atmospheric Sciences and Climate community workshop. This book describes the needs for end user communities, focusing in particular on needs that are not being met by current urban-level forecasting and monitoring. Urban Meteorology also describes current and emerging meteorological forecasting and monitoring capabilities that have had and will likely have the most impact on urban areas, some of which are not being utilized by the relevant end user communities. Urban Meteorology explains that users of urban meteorological information need high-quality information available in a wide variety of formats that foster its use and within time constraints set by users' decision processes. By advancing the science and technology related to urban meteorology with input from key end user communities, urban meteorologists can better meet the needs of diverse end users. To continue the advancement within the field of urban meteorology, there are both short-term needs-which might be addressed with small investments but promise large, quick returns-as well as future challenges that could require significant efforts and investments.
