Download or read book Synergy of Radar Lidar and Infrared Spectrometry to Retrieve Microphysical and Radiative Properties of Cirrus Clouds written by Andreas Reichegger and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization of Cirrus Clouds from Ground based Remote Sensing Using the Synergy of Lidar and Multi spectral Infrared Radiometry written by Friederike Hemmer and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is a broad consensus that cirrus clouds strongly influence the climate of the Earth. However, their net radiative effect is still poorly quantified nowadays due to an insufficient knowledge of their microphysical properties. This thesis aims to improve our understanding of the complex microphysics of this cloud type mainly composed of irregularly shaped ice crystals and thereby improve estimates of the ice water content (IWC). For this purpose, we developed an algorithm to retrieve vertical profiles of the IWC of cirrus clouds. The methodology combines the measurements of a ground-based lidar and a thermal infrared (TIR) radiometer in a common optimal estimation framework. It follows three steps: (1) An algorithm to retrieve the vertically integrated amount of ice (ice water path, IWP) from the passive TIR measurements is established. (2) The information about the vertical distribution of the IWC inside the cloud is obtained from the active lidar measurements. These retrievals strongly depend on the backscatter-to-extinction ratio of the ice crystals which is obtained from a bulk ice microphysical model. The scattering phase function of this model used to define the backscatter-to-extinction ratio assumes a flat ending without backscattering peak. We show that this assumption is unrealistic since it results in the retrieval of IWC profiles which are inconsistent with the TIR measurements. (3) Consequently, both types of measurements are combined in a synergistic algorithm allowing to estimate together with the IWC profiles a correction factor for the phase function in backscattering direction. Finally, the retrieval results and associated hypotheses are discussed.
Download or read book Cirrus written by David K. Lynch and published by Oxford University Press, USA. This book was released on 2002 with total page 499 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text, devoted entirely to cirrus clouds, captures the state of knowledge of cirrus clouds and serves as a practical handbook as well.
Download or read book A Characterization of Cirrus Cloud Properties That Affect Laser Propagation written by and published by . This book was released on 2008 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Future high-altitude laser systems may be affected by cirrus clouds. Laser transmission models were applied to measured and retrieved cirrus properties to determine cirrus impact on power incident on a target or receiver. A major goal was to see how well radiosondes and geostationary satellite imagery could specify the required properties. Based on the use of ground-based radar and lidar measurements as a reference, errors in cirrus-top and cirrus-base height estimates from radiosonde observations were 20%- 25% of geostationary satellite retrieval errors. Radiosondes had a perfect cirrus detection rate as compared with 80% for satellite detection. Ice water path and effective particle size were obtained with a published radar-lidar retrieval algorithm and a documented satellite algorithm. Radar-lidar particle size and ice water path were 1.5 and 3 times the satellite retrievals, respectively. Radar-lidar-based laser extinction coefficients were 55% greater than satellite values. Measured radar-lidar cirrus thickness was consistently greater than satellite-retrieved thickness, but radar-lidar microphysical retrieval required detection by both sensors at each range gate, which limited the retrievals' vertical extent. Greater radar-lidar extinction and greater satellite-based cirrus thickness yielded comparable optical depths for the two independent retrievals. Laser extinction-transmission models applied to radiosonde-retrieved cirrus heights and satellite-retrieved microphysical properties revealed a significant power loss by all models as the laser beam transits the cirrus layer. This suggests that cirrus location is more important than microphysics in high-altitude laser test support. Geostationary satellite imagery may be insufficient in cirrus detection and retrieval accuracy. Humidity-sensitive radiosondes are a potential proxy for ground-based remote sensors in cirrus detection and altitude determination.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Improvements in Modeling the Microphysical and Radiative Properties of Cirrus Clouds Using the Regional Atmospheric Modeling System RAMS Final Report written by and published by . This book was released on 1998 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main work activity during this period was the refinement and GCM parameterization of the treatment of ice cloud radiative properties, developed for this project. The treatment has now been rigorously tested and improved, and can now be used with confidence in radiation transfer schemes. The ice Cloud radiation scheme has also proven useful in satellite remote sensing. The radiation scheme differs from others in the thermal infrared, where it is assumed that photon tunneling does not occur for real ice particles (tunneling can be viewed as a process by which photons outside a particle's area-cross section can still be absorbed). Single particle T-matrix and Mie calculations suggest that a particle's ability to capture energy through tunneling depends on surface morphology, with more tunneling the more circular (or less angular) a surface is. This assumption leads to retrievals of mean particle size which are similar to those observed in tropical cirrus by optical imaging probes, whereas retrieved sizes using Mie theory are about 1/3 those predicted by this scheme. The retrieval method requires channels in the 8--9 [mu]m and 11--12 [mu]m ranges. This assumption about tunneling, as well as treating size distributions in the radiation scheme as bimodal, allows retrievals over a broader range of mean particle size than previous schemes permitted, making such size retrievals applicable to most types of cirrus clouds.
Download or read book Remote Sensing of Clouds and Precipitation written by Constantin Andronache and published by Springer. This book was released on 2018-02-21 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents current applications of remote sensing techniques for clouds and precipitation for the benefit of students, educators, and scientists. It covers ground-based systems such as weather radars and spaceborne instruments on satellites. Measurements and modeling of precipitation are at the core of weather forecasting, and long-term observations of the cloud system are vital to improving atmospheric models and climate projections. The first section of the book focuses on the use of ground-based weather radars to observe and measure precipitation and to detect and forecast storms, thunderstorms, and tornadoes. It also discusses the observation of clouds using ground-based millimeter radar. The second part of the book concentrates on spaceborne remote sensing of clouds and precipitation. It includes cases from the Tropical Rainfall Measuring Mission (TRMM) and the Global Precipitation Measurement (GPM) mission, using satellite radars to observe precipitation systems. Then, the focus is on global cloud observations from the ClaudSat, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), including a perspective on the Earth Clouds, Aerosols, and Radiation Explorer (EarthCARE) satellite. It also addresses global atmospheric water vapor profiling for clear and cloudy conditions using microwave observations. The final part of this volume provides a perspective into advances in cloud modeling using remote sensing observations.
Download or read book Cirrus Cloud Microphysical Property Retrieval Using Lidar and Radar Measurements written by Zhien Wang and published by . This book was released on 2002 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Basic Comparison of Lidar and Radar for Remote Sensing of Clouds written by Vernon Ellsworth Derr and published by . This book was released on 1978 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: Both radar and lidar have proved valuable in studying cloud microphysics and dynamics. Because of the large difference in wavelength, the two techniques have differing penetration capabilities and detection sensitivities. A "system-free" comparison of radar and lidar for several missions and many cloud types is presented to permit the optimum choice of technique for field studies of cloud formation, development, and precipitation.
Download or read book Observations of Tropical Cirrus by Elastic Backscatter Lidars and the Development of a Cloud and Aerosol Retrieval Algorithm for Raman Lidars written by Tyler J. Thorsen and published by . This book was released on 2014 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tropical cirrus cloud properties from elastic backscatter lidars--- namely the Atmospheric Radiation Measurement (ARM) program's ground-based micropulse lidars (MPL) and the spaceborne Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) lidar--- are examined. The MPL detects significantly less cirrus clouds relative to CALIPSO, particularly during the daytime. However, the MPL samples enough cirrus at night to provide similar statistics of macrophysical and optical properties as CALIPSO. Both sets of lidar observations are supplemented with cloud radar observations to calculate radiative heating rate profiles from a ground-based and spaceborne perspective. The inferred radiative effect of clouds is much smaller when using the ground-based data, mostly due to the lack of cirrus detected by the MPL. The relatively new and more advance ARM Raman lidar (RL) is shown to be more sensitive to cirrus than the ARM MPL and detects a similar amount of cirrus as CALIPSO. Daytime measurements using the RL elastic channel are relatively unaffected by the solar background and are therefore suited for checking the observed diurnal cycles from the MPL and CALIPSO. Comparisons with RL observations show that the geometrical thickness of cirrus from the MPL and CALIPSO datasets are biased thin during the daytime due to increased noise. Various upgrades since its conception have made the ARM RL a viable tool for cloud studies as demonstrated by this thesis. Since the ARM RL was not originally designed for cloud observations, the current automated processing algorithms do not identify all clouds nor attempt to retrieve cloud extinction profiles. Therefore an improved Feature detection and EXtinction retrieval (FEX) algorithm is developed. The approach of FEX is to use multiple quantities to identify features (clouds and aerosols) using range-dependent context-sensitive detection thresholds. The use of multiple quantities provides complementary depictions of cloud and aerosol locations. The extinction profiles are directly retrieved using the Raman method, which are supplemented by other retrieval methods developed for elastic backscatter lidars. A classification of feature type is made guided by the atmosphere's thermodynamic state and the feature's scattering properties. The contribution of multiple scattering, which is significant for hydrometeors, is explicitly considered for each of the ARM RL channels. The FEX framework is also suitable for other advance lidars, i.e. high spectral resolution lidars (HSRL). The continuously operated, automated ARM RLs paired with FEX provide an enormous wealth of water vapor, temperature, aerosol and cloud data unmatched by other remote sensing systems.
Download or read book Investigation of Thin Cirrus Cloud Optical and Microphysical Properties on the Basis of Satellite Observations and Fast Radiative Transfer Models written by Chenxi Wang and published by . This book was released on 2013 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on the global investigation of optically thin cirrus cloud optical thickness [tau] and microphysical properties, such as, effective particle size (D_(eff)) and ice crystal habits (shapes), based on the global satellite observations and fast radiative transfer models (RTMs). In the first part, we develop two computationally efficient RTMs simulating satellite observations under cloudy-sky conditions in the visible/shortwave infrared (VIS/SWIR) and thermal inferred (IR) spectral regions, respectively. To mitigate the computational burden associated with absorption, thermal emission and multiple scattering, we generate pre-computed lookup tables (LUTs) using two rigorous models, i.e., the line-by-line radiative transfer model (LBLRTM) and the discrete ordinates radiative transfer model (DISORT). The second part introduces two methods (i.e., VIS/SWIR- and IR-based methods) to retrieve [tau] and D_(eff) from satellite observations in corresponding spectral regions of the two RTMs. We discuss the advantages and weakness of the two methods by estimating the impacts from different error sources on the retrievals through sensitivity studies. Finally, we develop a new method to infer the scattering phase functions of optically thin cirrus clouds in a water vapor absorption channel (1.38-[mu]m). We estimate the ice crystal habits and surface structures by comparing the inferred scattering phase functions and numerically simulated phase functions calculated using idealized habits. We find two critical features of the two retrieval methods: (1) the IR-based method is more sensitive to optically thin cirrus cloud, and (2) the VIS/SWIR-based method is more sensitive to the pre-assumed ice cloud microphysical parameterization schemes. We derive the optically thin cirrus cloud phase functions based on the two methods. We find that small column-like particles (e.g., solid columns and column-aggregates) and droxtals with rough surfaces are likely to reside in optically thin cirrus clouds. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151213
Download or read book FIRE Cirrus Science Results 1993 written by David S. McDougal and published by . This book was released on 1993 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of Cloud Microphysical Property Retrievals in a Vertically Stratified Cirrus Cloud written by Erik R. Olson and published by . This book was released on 2000 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fast Processes in Large Scale Atmospheric Models written by Yangang Liu and published by John Wiley & Sons. This book was released on 2023-12-11 with total page 483 pages. Available in PDF, EPUB and Kindle. Book excerpt: Improving weather and climate prediction with better representation of fast processes in atmospheric models Many atmospheric processes that influence Earth’s weather and climate occur at spatiotemporal scales that are too small to be resolved in large scale models. They must be parameterized, which means approximately representing them by variables that can be resolved by model grids. Fast Processes in Large-Scale Atmospheric Models: Progress, Challenges and Opportunities explores ways to better investigate and represent multiple parameterized processes in models and thus improve their ability to make accurate climate and weather predictions. Volume highlights include: Historical development of the parameterization of fast processes in numerical models Different types of major sub-grid processes and their parameterizations Efforts to unify the treatment of individual processes and their interactions Top-down versus bottom-up approaches across multiple scales Measurement techniques, observational studies, and frameworks for model evaluation Emerging challenges, new opportunities, and future research directions The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals.
Download or read book Monte Carlo Simulation of Detection of Cirrus Cloud Properties by Micro Pulse Lidar written by James A. Cotturone and published by . This book was released on 1996-05-01 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of the Micro Pulse Lidar (MPL) provides researchers with a system capable of continuous, eye-safe monitoring of atmospheric properties. The MPL operates with low energy, high pulse repetition frequency radiation in the visible portion of the spectrum. To investigate the interaction between visible radiation and atmospheric constituents, a model using Monte Carlo techniques has been refined to simulate MPL return profiles. An inherent feature of the MPL is its narrow receiver field of view (FOV) which is necessary to limit background noise. The effect of such a FOV and the role multiple scattering effects play in MPL operations are investigated in this study. Cloud base height and the radiative properties of cirrus clouds are important for determining the radiation budget of the planet. Inferred cirrus cloud radiative properties vary with the type of crystals assumed to compose the model clouds. To properly model optically thin clouds, it is important to include a standard background atmosphere composed of Rayleigh and aerosol scatterers. Its inclusion allows one to take advantage of information deduced from both the cloud and above-cloud layer. Information that is unavailable when sampling optically thick clouds. This capability plays a pivotal role in an inversion algorithm that is developed and described. It is shown that the algorithm allows one to infer important cloud optical properties such as volume extinction coefficient, cloud optical depth, and isotropic backscatter to extinction ratio, also known as the lidar ratio.
Download or read book Investigation on Cirrus Clouds by the Cloud aerosol Lidar and Infrared Pathfinder Satellite Observation Data written by Jiang Zhu and published by . This book was released on 2011 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding and describing the role of clouds in the climate system need intensive and extensive research on cloud properties. The albedo and greenhouse effects of clouds and their relations with the physical properties of clouds are analyzed. Cloud-top height and ice water content are key factors in impacting the longwave and shortwave radiation, respectively. Lidar and infrared radiometer measurement technologies are introduced. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) level I Lidar profile, level 2 cloud layer, and level 2 Lidar/IIR track products are briefly reviewed. The algorithms for identification of cirrus clouds, Linear Depolarization Ratio (LDR), and effective diameter are presented. An average LDR profile is calculated by using the sum of total attenuated backscattering profiles and the sum of perpendicular attenuated backscattering profiles. A weight-average method is applied to calculate the average LDR. A split-window method is applied to estimate the effective diameters of clouds. A set of bulk ice crystal models and a radiative transfer model are applied to produce a look-up table that includes the radiative transfer simulation results. The macro-physical properties of cirrus clouds are analyzed. The frequency of occurrence of cirrus clouds varies with latitude, and strongly relates to the atmospheric circulation. Cirrus clouds are few in high-pressure zones and abundant where seasonal monsoonal circulation occurs. Cloud-top height decreases with increasing latitude. Cloud-top temperature is lower in the tropical regions than in the midlatutude and the polar regions. The measured cloud thickness shows a great diurnal variation. CALIPSO lidar detects more cirrus clouds than satellite-based passive measurement. LDR values of cirrus clouds vary with latitude and location, and are higher during nighttime than during daytime. The 0.32 and 0.37 annual average LDRs derived by nadir and off-nadir measurements, respectively, indicate that substantial amounts of horizontal orientated ice crystals exist in cirrus clouds. The global distribution of effective diameter of cirrus clouds varies with latitude and season, and the effective diameter has relationship with the LDR.
Download or read book The retrieval of cloud radiative and microphysical properties using combined near infrared and microwave radiometry written by J.P. TAYLOR and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
