scholarly journals First Odin sub-mm retrievals in the tropical upper troposphere: humidity and cloud ice signals

2007 ◽  
Vol 7 (2) ◽  
pp. 459-469 ◽  
Author(s):  
M. Ekström ◽  
P. Eriksson ◽  
B. Rydberg ◽  
D. P. Murtagh
Keyword(s):  
Careful Analysis ◽  
Systematic Difference ◽  
Horizontal Distribution ◽  
Calibration Error ◽  
Main Concern ◽  
Random Component ◽  
Worst Case ◽  
First Results ◽  
Ice Content ◽  
Cloud Ice

Abstract. Odin-SMR is a limb-sounder operating in the 500 GHz region with the capability of performing measurements down to altitudes of about 10 km with relatively low influence of ice clouds. Until now spectra from tropospheric tangent altitudes have been disregarded due to inadequate handling of scattering. A first method to extract upper tropospheric quantities has now been developed, yielding the humidity in two layers around 200 and 130 hPa and information on cloud ice content above 200 hPa. First results are compared with in situ MOZAIC measurements and presented to give a global view of the horizontal distribution. The seasonal structures are in agreement with other satellite measurements. The main concern for these retrievals is the calibration performance. A careful analysis indicates a systematic calibration error of about 1 K, but also a random component that differs between the two bands. The random calibration uncertainty results in retrieval errors of 10–60% depending on humidity and band. Presently this prohibits use of single retrievals, but averages can be presented with good accuracy. The fixed calibration error can largely be removed, leaving the spectroscopic uncertainties to dominate the humidity retrieval accuracy, with a worst case estimate of 30%. However, the comparison of MOZAIC data and the measurements for the 200 hPa layer shows a systematic difference of <10%. This indicates that the actual systematic error is low and gives further confidence in the capability of Odin-SMR to measure humidity in the upper tropical troposphere.

scholarly journals First Odin sub-mm retrievals in the tropical upper troposphere: humidity and cloud ice signals

2006 ◽  
Vol 6 (5) ◽  
pp. 8649-8680 ◽  
Author(s):  
M. Ekström ◽  
P. Eriksson ◽  
B. Rydberg ◽  
D. P. Murtagh
Keyword(s):  
Careful Analysis ◽  
Calibration Error ◽  
Main Concern ◽  
Random Component ◽  
Ice Clouds ◽  
Calibration Uncertainty ◽  
First Results ◽  
Tropical Troposphere ◽  
Ice Content ◽  
Cloud Ice

Abstract. Odin-SMR is a limb-sounder operating in the 500 region with the capability of performing measurements down to altitudes of about 10 with relatively low influence of ice clouds. Until now spectra from tropospheric tangent altitudes have been disregarded due to inadequate handling of scattering. A first method to extract upper tropospheric quantities has now been developed, yielding the humidity in two layers around 200 and 130 and information on cloud ice content above 200. The main concern for these retrievals is the calibration performance. A careful analysis indicates a systematic calibration error of about 1 K, but also a random component that differs between the two bands. The random calibration uncertainty results in retrieval errors of 10–60% depending on humidity and band. Presently this prohibits use of single retrievals, but averages can be presented with good accuracy. The fixed calibration error can largely be removed, leaving the spectroscopic uncertainties to dominate the humidity retrieval accuracy, estimated to be around 20%. First results are presented that are in agreement with seasonal structure obtained from other satellite measurements. An encouraging comparison between MOZAIC data and measurements for the 200 layer gives further confidence in the capability of Odin-SMR to measure humidity in the upper tropical troposphere.

The Price of Order

2016 ◽  
Vol 26 (03n04) ◽  
pp. 135-149
Author(s):  
Prosenjit Bose ◽  
Pat Morin ◽  
André van Renssen
Keyword(s):  
Lower Bounds ◽  
Large Family ◽  
Worst Case ◽  
Graph Partitions ◽  
First Results

We present tight bounds on the spanning ratio of a large family of ordered [Formula: see text]-graphs. A [Formula: see text]-graph partitions the plane around each vertex into [Formula: see text] disjoint cones, each having aperture [Formula: see text]. An ordered [Formula: see text]-graph is constructed by inserting the vertices one by one and connecting each vertex to the closest previously-inserted vertex in each cone. We show that for any integer [Formula: see text], ordered [Formula: see text]-graphs with [Formula: see text] cones have a tight spanning ratio of [Formula: see text]. We also show that for any integer [Formula: see text], ordered [Formula: see text]-graphs with [Formula: see text] cones have a tight spanning ratio of [Formula: see text]. We provide lower bounds for ordered [Formula: see text]-graphs with [Formula: see text] and [Formula: see text] cones. For ordered [Formula: see text]-graphs with [Formula: see text] and [Formula: see text] cones these lower bounds are strictly greater than the worst case spanning ratios of their unordered counterparts. These are the first results showing that ordered [Formula: see text]-graphs have worse spanning ratios than unordered [Formula: see text]-graphs. Finally, we show that, unlike their unordered counterparts, the ordered [Formula: see text]-graphs with 4, 5, and 6 cones are not spanners.

Optimally Unstable Underactuated Gripper: Synthesis and Applications

2006 ◽  
Author(s):  
Lionel Birglen ◽  
Cle´ment M. Gosselin
Keyword(s):  
Careful Analysis ◽  
Equilibrium Curve ◽  
First Results

This paper presents the synthesis of optimally unstable two-phalanx underactuated fingers. The method to obtain a design unable to grasp almost any object under normal conditions is presented. The technique relies on the careful analysis of the grasp-state plane and equilibrium curve associated to two-phalanx underactuated fingers. First, results of the analysis of the grasp-state plane are recalled. Second, unstable configurations and paradoxical equilibrium are presented. Then, the synthesis of optimally unstable fingers is detailed. Finally, applications of these unstable fingers are proposed.

scholarly journals Observing relationships between lightning and cloud profiles by means of a satellite-borne cloud radar

2017 ◽  
Vol 10 (1) ◽  
pp. 221-230 ◽  
Author(s):  
Martina Buiat ◽  
Federico Porcù ◽  
Stefano Dietrich
Keyword(s):  
Vertical Distribution ◽  
Lightning Activity ◽  
Convective Clouds ◽  
Ice Particles ◽  
Ice Water Content ◽  
Ice Content ◽  
Cloud Ice ◽  
Ice Water ◽  
The Vertical Distribution ◽  
Polar Satellite

Abstract. Cloud electrification and related lightning activity in thunderstorms have their origin in the charge separation and resulting distribution of charged iced particles within the cloud. So far, the ice distribution within convective clouds has been investigated mainly by means of ground-based meteorological radars. In this paper we show how the products from Cloud Profiling Radar (CPR) on board CloudSat, a polar satellite of NASA's Earth System Science Pathfinder (ESSP), can be used to obtain information from space on the vertical distribution of ice particles and ice content and relate them to the lightning activity. The analysis has been carried out, focusing on 12 convective events over Italy that crossed CloudSat overpasses during significant lightning activity. The CPR products considered here are the vertical profiles of cloud ice water content (IWC) and the effective radius (ER) of ice particles, which are compared with the number of strokes as measured by a ground lightning network (LINET). Results show a strong correlation between the number of strokes and the vertical distribution of ice particles as depicted by the 94 GHz CPR products: in particular, cloud upper and middle levels, high IWC content and relatively high ER seem to be favourable contributory causes for CG (cloud to ground) stroke occurrence.

An Indirect Effect of Ice Nuclei on Atmospheric Radiation

2009 ◽  
Vol 66 (1) ◽  
pp. 41-61 ◽  
Author(s):  
Xiping Zeng ◽  
Wei-Kuo Tao ◽  
Minghua Zhang ◽  
Arthur Y. Hou ◽  
Shaocheng Xie ◽  
...  
Keyword(s):  
Indirect Effect ◽  
Large Scale ◽  
Three Dimensional ◽  
Radiative Flux ◽  
Middle Latitudes ◽  
Ice Nuclei ◽  
Cloud Resolving Model ◽  
Ice Content ◽  
Cloud Ice ◽  
The Tropics

Abstract A three-dimensional cloud-resolving model (CRM) with observed large-scale forcing is used to study how ice nuclei (IN) affect the net radiative flux at the top of the atmosphere (TOA). In all the numerical experiments carried out, the cloud ice content in the upper troposphere increases with IN number concentration via the Bergeron process. As a result, the upward solar flux at the TOA increases whereas the infrared one decreases. Because of the opposite response of the two fluxes to IN concentration, the sensitivity of the net radiative flux at the TOA to IN concentration varies from one case to another. Six tropical and three midlatitudinal field campaigns provide data to model the effect of IN on radiation in different latitudes. Classifying the CRM simulations into tropical and midlatitudinal and then comparing the two types reveals that the indirect effect of IN on radiation is greater in the middle latitudes than in the tropics. Furthermore, comparisons between model results and observations suggest that observational IN data are necessary to evaluate long-term CRM simulations.

Effect of Calibration Error on Bone Tracking Accuracy With Fluoroscopy

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Luca Tersi ◽  
Rita Stagni
Keyword(s):  
Pose Estimation ◽  
Linear Trend ◽  
Estimation Error ◽  
Image Plane ◽  
Joint Kinematics ◽  
Estimation Accuracy ◽  
Calibration Error ◽  
Tracking Accuracy ◽  
Case Scenario ◽  
Worst Case

Model-based 3D-fluoroscopy can quantify joint kinematics with 1 mm and 1 deg accuracy level. A calibration based on the acquisition of devices of known geometry is usually applied to size the system. This study aimed at quantifying the sensitivity of the fluoroscopic pose estimation accuracy specifically to errors in the calibration process, excluding other sources of error. X-ray focus calibration error was quantified for different calibration setups, and its propagation to the pose estimation was characterized in-silico. Focus reference position influenced the calibration error dispersion, while calibration cage pose affected its bias. In the worst-case scenario, the estimation error of the principal point and of the focus distance was lower than 1 mm and 2 mm, respectively. The consequent estimation of joint angles was scarcely influenced by calibration errors. A linear trend was highlighted for joint translations, with a sensitivity proportional to the distance between the model and the image plane, resulting in a submillimeter error for realistic calibration errors. The biased component of the error is compensated when computing relative joint kinematics between two segments.

scholarly journals It Started with Templates: The Future of Profiling in Side-Channel Analysis

2021 ◽  
pp. 133-145
Author(s):  
Lejla Batina ◽  
Milena Djukanovic ◽  
Annelie Heuser ◽  
Stjepan Picek
Keyword(s):  
Machine Learning ◽  
Supervised Machine Learning ◽  
Machine Learning Techniques ◽  
Side Channel ◽  
Side Channel Attacks ◽  
Worst Case ◽  
Learning Techniques ◽  
The Future ◽  
First Results ◽  
Channel Analysis

AbstractSide-channel attacks (SCAs) are powerful attacks based on the information obtained from the implementation of cryptographic devices. Profiling side-channel attacks has received a lot of attention in recent years due to the fact that this type of attack defines the worst-case security assumptions. The SCA community realized that the same approach is actually used in other domains in the form of supervised machine learning. Consequently, some researchers started experimenting with different machine learning techniques and evaluating their effectiveness in the SCA context. More recently, we are witnessing an increase in the use of deep learning techniques in the SCA community with strong first results in side-channel analyses, even in the presence of countermeasures. In this chapter, we consider the evolution of profiling attacks, and subsequently we discuss the impacts they have made in the data preprocessing, feature engineering, and classification phases. We also speculate on the future directions and the best-case consequences for the security of small devices.

scholarly journals Ice multiplication from ice–ice collisions in the high Arctic: sensitivity to ice habit, rimed fraction, ice type and uncertainties in the numerical description of the process

2021 ◽  
Vol 21 (12) ◽  
pp. 9741-9760
Author(s):  
Georgia Sotiropoulou ◽  
Luisa Ickes ◽  
Athanasios Nenes ◽  
Annica M. L. Ekman
Keyword(s):  
High Arctic ◽  
The Arctic ◽  
Atmospheric Models ◽  
Ocean Study ◽  
Ice Water Content ◽  
Ice Multiplication ◽  
Ice Content ◽  
Cloud Ice ◽  
Mixed Phase Clouds ◽  
Ice Water

Abstract. Atmospheric models often fail to correctly reproduce the microphysical structure of Arctic mixed-phase clouds and underpredict ice water content even when the simulations are constrained by observed levels of ice nucleating particles. In this study we investigate whether ice multiplication from breakup upon ice–ice collisions, a process missing in most models, can account for the observed cloud ice in a stratocumulus cloud observed during the Arctic Summer Cloud Ocean Study (ASCOS) campaign. Our results indicate that the efficiency of this process in these conditions is weak; increases in fragment generation are compensated for by subsequent enhancement of precipitation and subcloud sublimation. Activation of collisional breakup improves the representation of cloud ice content, but cloud liquid remains overestimated. In most sensitivity simulations, variations in ice habit and prescribed rimed fraction have little effect on the results. A few simulations result in explosive multiplication and cloud dissipation; however, in most setups, the overall multiplication effects become substantially weaker if the precipitation sink is enhanced through cloud-ice-to-snow autoconversion. The largest uncertainty stems from the correction factor for ice enhancement due to sublimation included in the breakup parameterization; excluding this correction results in rapid glaciation, especially in simulations with plates. Our results indicate that the lack of a detailed treatment of ice habit and rimed fraction in most bulk microphysics schemes is not detrimental for the description of the collisional breakup process in the examined conditions as long as cloud-ice-to-snow autoconversion is considered.

scholarly journals Validation of Backscatter Measurements from the Advanced Scatterometer on MetOp-A

2011 ◽  
Vol 29 (1) ◽  
pp. 77-88 ◽  
Author(s):  
C. Anderson ◽  
J. Figa ◽  
H. Bonekamp ◽  
J. J. W. Wilson ◽  
J. Verspeek ◽  
...  
Keyword(s):  
Incidence Angle ◽  
Absolute Calibration ◽  
Calibration Error ◽  
Wind Fields ◽  
Worst Case ◽  
Antarctic Sea Ice ◽  
Geophysical Model ◽  
Geophysical Model Function ◽  
Calibration Accuracy ◽  
Ocean Wind

Abstract The Advanced Scatterometer (ASCAT) on the Meteorological Operational (MetOp) series of satellites is designed to provide data for the retrieval of ocean wind fields. Three transponders were used to give an absolute calibration and the worst-case calibration error is estimated to be 0.15–0.25 dB. In this paper the calibrated data are validated by comparing the backscatter from a range of naturally distributed targets against models developed from European Remote Sensing Satellite (ERS) scatterometer data. For the Amazon rainforest it is found that the isotropic backscatter decreases from −6.2 to −6.8 dB over the incidence angle range. The ERS value is around −6.5 dB. All ASCAT beams are within 0.1 dB of each other. Rainforest backscatter over a 3-yr period is found to be very stable with annual changes of approximately 0.02 dB. ASCAT ocean backscatter is compared against values from the C-band geophysical model function (CMOD-5) using ECMWF wind fields. A difference of approximately 0.2 dB below 55° incidence is found. Differences of over 1 dB above 55° are likely due to inaccuracies in CMOD-5, which has not been fully validated at large incidence angles. All beams are within 0.1 dB of each other. Backscatter from regions of stable Antarctic sea ice is found to be consistent with model backscatter except at large incidence angles where the model has not been validated. The noise in the ice backscatter indicates that the normalized standard deviation of the backscatter values Kp is around 4.5%, which is consistent with the expected value. These results agree well with the expected calibration accuracy and give confidence that the calibration has been successful and that ASCAT products are of high quality.

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