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Thermal structure of intense convective clouds derived from GPS radio occultations
R. Biondi, W. J. Randel, S.-P. Ho, T. Neubert,S. Syndergaard
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2012,
Abstract: Thermal structure associated with deep convective clouds is investigated using Global Positioning System (GPS) radio occultation measurements. GPS data are insensitive to the presence of clouds, and provide high vertical resolution and high accuracy measurements to identify associated temperature behavior. Deep convective systems are identified using International Satellite Cloud Climatology Project (ISCCP) satellite data, and cloud tops are accurately measured using Cloud-Aerosol Lidar with Orthogonal Polarization (CALIPSO) lidar observations; we focus on 53 cases of near-coincident GPS occultations with CALIPSO profiles over deep convection. Results show a sharp spike in GPS bending angle highly correlated to the top of the clouds, corresponding to anomalously cold temperatures within the clouds. Above the clouds the temperatures return to background conditions, and there is a strong inversion at cloud top. For cloud tops below 14 km, the temperature lapse rate within the cloud often approaches a moist adiabat, consistent with rapid undiluted ascent within the convective systems.
A simplified approach for generating GNSS radio occultation refractivity climatologies  [PDF]
H. Gleisner,S. B. Healy
Atmospheric Measurement Techniques Discussions , 2012, DOI: 10.5194/amtd-5-5245-2012
Abstract: The possibility of simplifying the retrieval scheme required to produce GNSS radio occultation refractivity climatologies is investigated. In a new, simplified retrieval approach, the main statistical analysis is performed in bending angle space and an estimate of the average bending angle profile is then propagated through an Abel transform. The average is composed of means and medians of ionospheric corrected bending angles up to 80 km. Above that, the observed profile is exponentially extrapolated to infinity using a fixed a priori scale height. The new approach circumvents the need to introduce a "statistical optimization" processing step in which individual bending-angle profiles are merged with a priori data, often taken from a climatology. This processing step can be complex, difficult to interpret, and is generally recognized as a potential source of structural uncertainty. The new scheme is compared with the more conventional approach of averaging individual refractivity profiles, produced with the implementation of statistical optimization used in the EUMETSAT Radio Occultation Meteorology Satellite Application Facility (ROM SAF) operational processing. It is shown that the two GNSS radio occultation climatologies agree to within 0.1% from 5 km up to 35–40 km, for the three months January, February, and March 2011. During this time period, the new approach also produces slightly better agreement with ECMWF analyses between 40–50 km, which is encouraging. The possible limitations of the new approach caused by mean residual ionospheric errors and low observation numbers are discussed briefly, and areas for future work are suggested.
Radio occultation bending angle anomalies during tropical cyclones
R. Biondi, T. Neubert, S. Syndergaard,J. K. Nielsen
Atmospheric Measurement Techniques (AMT) & Discussions (AMTD) , 2011,
Abstract: The tropical deep convection affects the radiation balance of the atmosphere changing the water vapor mixing ratio and the temperature of the upper troposphere lower stratosphere. The aim of this work is to better understand these processes and to investigate if severe storms leave a significant signature in radio occultation profiles in the tropical tropopause layer. Using tropical cyclone best track database and data from different GPS radio occultation missions (COSMIC, GRACE, CHAMP, SACC and GPSMET), we selected 1194 profiles in a time window of 3 h and a space window of 300 km from the eye of the cyclone. We show that the bending angle anomaly of a GPS radio occultation signal is typically larger than the climatology in the upper troposphere and lower stratosphere and that a double tropopause during deep convection can easily be detected using this technique. Comparisons with co-located radiosondes, climatology of tropopause altitudes and GOES analyses are also shown to support the hypothesis that the bending angle anomaly can be used as an indicator of convective towers. The results are discussed in connection to the GPS radio occultation receiver which will be part of the Atomic Clock Ensemble in Space (ACES) payload on the International Space Station.
Radio occultation bending angle anomalies during tropical cyclones  [PDF]
R. Biondi,T. Neubert,S. Syndergaard,J. Nielsen
Atmospheric Measurement Techniques Discussions , 2011, DOI: 10.5194/amtd-4-1371-2011
Abstract: The tropical deep convection affects the radiation balance of the atmosphere changing the water vapor mixing ratio and the temperature of the upper troposphere lower stratosphere. The aim of this work is to better understand these processes and to investigate if severe storms leave a significant signature in radio occultation profiles in the tropical tropopause layer. Using tropical cyclone best track database and data from different GPS radio occultation missions (COSMIC, GRACE, CHAMP, SACC and GPSMET), we selected 1194 profiles in a time window of 3 h and a space window of 300 km from the eye of the cyclone. We show that the bending angle anomaly of a GPS radio occultation signal is typically larger than the climatology in the upper troposphere and lower stratosphere and that a double tropopause during deep convection can easily be detected using this technique. Comparisons with co-located radiosondes, climatology of tropopause altitudes and GOES analyses are also shown to support the hypothesis that the bending angle anomaly can be used as an indicator of convective towers. The results are discussed in connection to the GPS radio occultation receiver which will be part of the Atomic Clock Ensemble in Space (ACES) payload on the International Space Station.
Forthcoming occultations of astrometric radio sources by planets  [PDF]
Victor L'vov,Zinovy Malkin,Svetlana Tsekmeister
Physics , 2011,
Abstract: Astrometric observations of the radio source occultations by solar system bodies may be of large interest for testing gravity theories, dynamical astronomy, and planetary physics. In this paper, we present an updated list of the occultations of astrometric radio sources by planets expected in the nearest years. Such events, like the solar eclipses, generally speaking, can be only observed in a limited region. The map of the shadow path is provided for the events occurred in regions with several VLBI stations and hence the most interesting for radio astronomy experiments.
Numerical Investigation of the Effect of Process and Sheet Parameters on Bending Angle in the Laser Bending Process  [PDF]
Mehdi Safari
World Journal of Mechanics (WJM) , 2014, DOI: 10.4236/wjm.2014.44011
Abstract:

In this work, the effects of process parameters such as laser output power, beam diameter and scan speed and also sheet thickness on the bending angle have been numerically investigated in the laser bending process. For this purpose, Abaqus software is used for investigating the effect of various process and sheet parameters on the bending angle. The results show that with increasing the laser output power, bending angle is increased. Also, the bending angle is decreased with increasing the beam diameter, scan speed and sheet thickness.

STUDY THE EFFECT OF ANGLE DORSIFLEXION ON BENDING STRESS OF PROSTHETIC PYLON
MUSLIM M. ALI,ALI I. AL-MOSAWI,JABBAR H.MOHMMED,ALI R. YOUSIF
International Journal of Engineering Science and Technology , 2012,
Abstract: Affecting millions of people worldwide, artificial limbs and prosthetics are major topics in the field of bio mechatronics. This paper will examine and describe in effect of angle dorsiflexion on bending stress limb technology, in particular focusing on prosthetic pylon. The theoretical part includes; analytical solution to find dorsiflexion angle and bending stress. In the numerical method, the finite element is used by employing ANSYS package to find bending stress with angle dorsiflexion with gait cycle and Von Misses stresses. Thus the prosthetic pylon was angle dorsiflexionthe value of stress bending will be increased with increasing of angle dorsiflexion.
Transits and Occultations  [PDF]
Joshua N. Winn
Physics , 2010,
Abstract: When we are fortunate enough to view an exoplanetary system nearly edge-on, the star and planet periodically eclipse each other. Observations of eclipses (transits and occultations) provide a bonanza of information that cannot be obtained from radial-velocity data alone, such as the relative dimensions of the planet and its host star, as well as the orientation of the planet's orbit relative to the sky plane and relative to the stellar rotation axis. The wavelength-dependence of the eclipse signal gives clues about the the temperature and composition of the planetary atmosphere. Anomalies in the timing or other properties of the eclipses may betray the presence of additional planets or moons. Searching for eclipses is also a productive means of discovering new planets. This chapter reviews the basic geometry and physics of eclipses, and summarizes the knowledge that has been gained through eclipse observations, as well as the information that might be gained in the future.
Light's Bending Angle in the Equatorial Plane of a Kerr Black Hole  [PDF]
Savitri V. Iyer,Edward C. Hansen
Physics , 2009, DOI: 10.1103/PhysRevD.80.124023
Abstract: We present here a detailed derivation of an explicit spin-dependent expression for the bending angle of light as it traverses in the equatorial plane of a spinning black hole. We show that the deflection produced in the presence of the black hole angular momentum explicitly depends on whether the motion of the light ray is in the direction, or opposite to the spin. Compared to the zero-spin Schwarzschild case, the bending angle is greater for direct orbits, and {\em smaller} for retrograde orbits, confirming our physical intuition about the loss of left-right symmetry from a lensing perspective. In addition, we show that for higher spins, the effect is more pronounced resulting in tighter winding of direct orbits with respect to the axis of rotation, and a higher degree of unwinding of retro orbits. A direct consequence of this effect is a shift in image positions in strong gravitational lensing.
The Variational Assimilation Experiment of GPS Bending Angle
GPS折射角资料的变分同化试验

WANG Yunfeng,WANG Bin,
WANG Yunfeng
,WANG Bin

大气科学进展 , 2003,
Abstract: More and more new types of observational data provide many new opportunities for improving numericalweather forecasts. Among these, the GPS (Global Positioning System) bending angle is undoubtedly veryimportant. There are many advantages of the GPS bending angle, such as high resolution, availability inall weather conditions, and global data coverage. Thus it is very valuable to assimilate GPS bending angledata into numerical weather models. This paper introduces how to obtain and assimilate the GPS bendingangle. There are two methods of assimilation: the indirect method and direct method, and they are bothintroduced in this paper. During the minimizing process of variational assimilation, calculation efficiencyis very important and the optimal step size greatly influences the algorithm efficiency. Based on thecharacteristics of the minimizing algorithm, we obtain an adaptive method for calculating the optimizingstep suitable for all kinds of minimization algorithms through mathematical deduction. Finally, a numericalvariational assimilation experiment is performed using the GPS bending angle data of 11 October 1995.The numerical results indicate the validity of the variational assimilation method and the adaptive methodintroduced here.
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