The Experts below are selected from a list of 46899 Experts worldwide ranked by ideXlab platform
R P Lawson - One of the best experts on this subject based on the ideXlab platform.
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mixed phase boundary layer clouds observed from a tethered balloon platform in the arctic
RADIATION PROCESSES IN THE ATMOSPHERE AND OCEAN (IRS2012): Proceedings of the International Radiation Symposium (IRC IAMAS), 2013Co-Authors: Mehak Sikand, J Koskulics, Knut Stamnes, Borge Hamre, Jakob J Stamnes, R P LawsonAbstract:Microphysical and radiative measurements in boundary-layer mixed-phase clouds were collected during a May-June 2008 tethered balloon campaign in Ny-Alesund, Norway in the high Arctic. The instruments deployed on the tethered balloon platform included a Radiometer, a cloud particle imager, and a meteorological package. The mean intensities estimated from the Radiometer measurements on the balloon were used to quantify the vertical structure of the mixed phase cloud system, while the downward irradiances measured by an upward looking ground-based Radiometer were used to constrain the total cloud optical depth. The time evolution of the liquid water and ice particle cloud optical depths was estimated by using a comprehensive radiative transfer model.
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estimation of mixed phase cloud optical depth and position using in situ radiation and cloud microphysical measurements obtained from a tethered balloon platform
Journal of the Atmospheric Sciences, 2013Co-Authors: Mehak Sikand, Knut Stamnes, Borge Hamre, Jakob J Stamnes, R P LawsonAbstract:Microphysical and radiative measurements in boundarylayer mixed-phaseclouds(MPCs), consisting of ice crystals and liquid droplets, have been analyzed. These cloud measurements were collected during a May- June 2008 tethered-balloon campaign in Ny-Alesund, Norway, located at 78.98N, 11.98E in the High Arctic. The instruments deployed on the tethered-balloon platform included a Radiometer, a cloud particle imager (CPI), and a meteorological package. To analyze the data, a radiative transfer model (RTM) was constructed with two cloud layers—consistent with the CPI data—embedded in a background Rayleigh scattering at- mosphere. The mean intensities estimated from the Radiometer measurements on the balloon were used in conjunction with the RTM to quantify the vertical structure of the MPC system, while the downward irra- diances measured by an upward-looking ground-based Radiometer were used to constrain the total cloud optical depth. The time series of Radiometer and CPI data obtained while profiling the cloud system was used to estimate the time evolutionof the liquid water and ice particle optical depths as well as the vertical location of the two cloud layers.
Graham Machin - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic temperature by primary radiometry
Philosophical Transactions of the Royal Society A, 2016Co-Authors: Klaus Anhalt, Graham MachinAbstract:Above the freezing temperature of silver (1234.93 K), the International Temperature Scale of 1990 (ITS-90) gives a temperature, T 90 , in terms of a defining fixed-point blackbody and Planck9s law of thermal radiation in ratio form. Alternatively, by using Planck9s law directly, thermodynamic temperature can be determined by applying radiation detectors calibrated in absolute terms for their spectral responsivity. With the advent of high-quality semiconductor photodiodes and the development of high-accuracy cryogenic Radiometers during the last two decades radiometric detector standards with very small uncertainties in the range of 0.01–0.02% have been developed for direct, absolute radiation thermometry with uncertainties comparable to those for the realization of the ITS-90. This article gives an overview of a number of design variants of different types of Radiometer used for primary radiometry and describes their calibration. Furthermore, details and requirements regarding the experimental procedure for obtaining low uncertainty thermodynamic temperatures with these Radiometers are presented, noting that such Radiometers can also be used at temperatures well below the silver point. Finally, typical results obtained by these methods are reviewed.
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thermodynamic temperature determinations of co c pd c pt c and ru c eutectic fixed point cells
Metrologia, 2006Co-Authors: Klaus Anhalt, Graham Machin, J T Hartmann, D. Lowe, Mohamed Sadli, Yoshiro YamadaAbstract:Thermodynamic temperatures during the melt and the freeze of Co?C, Pd?C, Pt?C and Ru?C metal?carbon fixed-point cells manufactured by LNE?INM/CNAM, NMIJ and NPL were determined by absolutely calibrated filter Radiometers traceable to the PTB cryogenic Radiometer and a radiance comparison method using an IKE LP3 radiation thermometer. The measurement uncertainties were below 400?mK at temperatures up to 2250?K. The results are in agreement within the combined uncertainties with a study on relative temperature differences of the same set of fixed-point cells. For the fixed-point cells manufactured by NPL the results are compared with a previous thermodynamic temperature measurement.
Klaus Anhalt - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic temperature by primary radiometry
Philosophical Transactions of the Royal Society A, 2016Co-Authors: Klaus Anhalt, Graham MachinAbstract:Above the freezing temperature of silver (1234.93 K), the International Temperature Scale of 1990 (ITS-90) gives a temperature, T 90 , in terms of a defining fixed-point blackbody and Planck9s law of thermal radiation in ratio form. Alternatively, by using Planck9s law directly, thermodynamic temperature can be determined by applying radiation detectors calibrated in absolute terms for their spectral responsivity. With the advent of high-quality semiconductor photodiodes and the development of high-accuracy cryogenic Radiometers during the last two decades radiometric detector standards with very small uncertainties in the range of 0.01–0.02% have been developed for direct, absolute radiation thermometry with uncertainties comparable to those for the realization of the ITS-90. This article gives an overview of a number of design variants of different types of Radiometer used for primary radiometry and describes their calibration. Furthermore, details and requirements regarding the experimental procedure for obtaining low uncertainty thermodynamic temperatures with these Radiometers are presented, noting that such Radiometers can also be used at temperatures well below the silver point. Finally, typical results obtained by these methods are reviewed.
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thermodynamic temperature determinations of co c pd c pt c and ru c eutectic fixed point cells
Metrologia, 2006Co-Authors: Klaus Anhalt, Graham Machin, J T Hartmann, D. Lowe, Mohamed Sadli, Yoshiro YamadaAbstract:Thermodynamic temperatures during the melt and the freeze of Co?C, Pd?C, Pt?C and Ru?C metal?carbon fixed-point cells manufactured by LNE?INM/CNAM, NMIJ and NPL were determined by absolutely calibrated filter Radiometers traceable to the PTB cryogenic Radiometer and a radiance comparison method using an IKE LP3 radiation thermometer. The measurement uncertainties were below 400?mK at temperatures up to 2250?K. The results are in agreement within the combined uncertainties with a study on relative temperature differences of the same set of fixed-point cells. For the fixed-point cells manufactured by NPL the results are compared with a previous thermodynamic temperature measurement.
Mehak Sikand - One of the best experts on this subject based on the ideXlab platform.
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mixed phase boundary layer clouds observed from a tethered balloon platform in the arctic
RADIATION PROCESSES IN THE ATMOSPHERE AND OCEAN (IRS2012): Proceedings of the International Radiation Symposium (IRC IAMAS), 2013Co-Authors: Mehak Sikand, J Koskulics, Knut Stamnes, Borge Hamre, Jakob J Stamnes, R P LawsonAbstract:Microphysical and radiative measurements in boundary-layer mixed-phase clouds were collected during a May-June 2008 tethered balloon campaign in Ny-Alesund, Norway in the high Arctic. The instruments deployed on the tethered balloon platform included a Radiometer, a cloud particle imager, and a meteorological package. The mean intensities estimated from the Radiometer measurements on the balloon were used to quantify the vertical structure of the mixed phase cloud system, while the downward irradiances measured by an upward looking ground-based Radiometer were used to constrain the total cloud optical depth. The time evolution of the liquid water and ice particle cloud optical depths was estimated by using a comprehensive radiative transfer model.
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estimation of mixed phase cloud optical depth and position using in situ radiation and cloud microphysical measurements obtained from a tethered balloon platform
Journal of the Atmospheric Sciences, 2013Co-Authors: Mehak Sikand, Knut Stamnes, Borge Hamre, Jakob J Stamnes, R P LawsonAbstract:Microphysical and radiative measurements in boundarylayer mixed-phaseclouds(MPCs), consisting of ice crystals and liquid droplets, have been analyzed. These cloud measurements were collected during a May- June 2008 tethered-balloon campaign in Ny-Alesund, Norway, located at 78.98N, 11.98E in the High Arctic. The instruments deployed on the tethered-balloon platform included a Radiometer, a cloud particle imager (CPI), and a meteorological package. To analyze the data, a radiative transfer model (RTM) was constructed with two cloud layers—consistent with the CPI data—embedded in a background Rayleigh scattering at- mosphere. The mean intensities estimated from the Radiometer measurements on the balloon were used in conjunction with the RTM to quantify the vertical structure of the MPC system, while the downward irra- diances measured by an upward-looking ground-based Radiometer were used to constrain the total cloud optical depth. The time series of Radiometer and CPI data obtained while profiling the cloud system was used to estimate the time evolutionof the liquid water and ice particle optical depths as well as the vertical location of the two cloud layers.
F S Marzano - One of the best experts on this subject based on the ideXlab platform.
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exploiting tropospheric measurements from sun tracking Radiometer for radiopropagation models at centimeter and millimeter wave
IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2019Co-Authors: M Biscarini, Mario Montopoli, Luca Milani, Klaide De Sanctis, Saverio Di Fabio, Kevin M Magde, George A Brost, F S MarzanoAbstract:The objective of this paper is to characterize the atmospheric radiometeorological parameters (optical thickness and brightness temperature) at centimeter and millimeter waves. To this aim, we have exploited two radiative transfer models (RTMs): a three-dimensional model (3D-RTM), driven by numerical weather forecasts, and a stochastic one-dimensional (1-D) model (1D-RTM), fed by a synthetic clouds dataset. We have compared the radiative transfer simulations with measurements from two ground-based microwave Radiometers: a profiler and a Sun-tracking Radiometer. The peculiarity of the latter is the capacity of simultaneously measuring atmospheric optical thickness and brightness temperature in all-weather conditions and at variable elevation angles. The comparisons between simulations and measurements provide satisfactory results that assess the reliability of the 3D-RTM with some biases, in terms of brightness temperature, that should be investigated. 3D-RTM turns out to be able to successfully reproduce correlations between brightness temperature and optical thickness and correlations among the different frequency channels. This confirms the potential of the combined use of weather forecast models and physically-based RTMs. On the other hand, 1D-RTM reveals to be able to reproduce frequency-channel correlation trends, but additional climatological set-up are needed to make the model exploitable for the computation of statistics of atmospheric optical thickness. These comparisons also highlight some possible calibration errors in the Sun-tracking Radiometer that must be fixed. Finally, we have exploited measurements from the Sun-tracking Radiometer to develop a model to retrieve the probability of atmospheric optical thickness conditioned to a given elevation angle.
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flower constellation of millimeter wave Radiometers for tropospheric monitoring at pseudogeostationary scale
IEEE Transactions on Geoscience and Remote Sensing, 2009Co-Authors: F S Marzano, D Cimini, A Memmo, Mario Montopoli, T Rossi, M C De Sanctis, M Lucente, Daniele Mortari, S Di MicheleAbstract:In this paper, the design of a minisatellite FLOwer constellation (FC), deploying millimeter-wave (MMW) scanning Radiometers, namely, FLORAD, and devoted to tropospheric observations, is analyzed and discussed. The FLORAD mission is aimed at the retrieval of thermal and hydrological properties of the troposphere, specifically temperature profile, water-vapor profile, cloud liquid content, and rainfall and snowfall rate. The goal of frequent revisit time at regional scale, coupled with quasi-global coverage and relatively high spatial resolution, is here called pseudogeostationary scale and implemented through a FC of three minisatellites in elliptical orbits. FCs are built on compatible (resonant) orbits and can offer several degrees of freedom in their design. The payload MMW channels for tropospheric retrieval were selected following the ranking based on a reduced-entropy method between 90 and 230 GHz. Various configurations of the MMW Radiometer multiband channels are investigated, pointing out the tradeoff between performances and complexity within the constraint of minisatellite platform. Statistical inversion schemes are employed to quantify the overall accuracy of the selected MMW Radiometer configurations.
