scholarly journals A Study of Sea Surface Rain Identification Based on HY-2A Scatterometer

2021 ◽  
Vol 13 (17) ◽  
pp. 3475
Author(s):  
Yihuan Peng ◽  
Xuetong Xie ◽  
Mingsen Lin ◽  
Lishan Ran ◽  
Feng Yuan ◽  
...  
Keyword(s):  
Wind Field ◽  
Mean Deviation ◽  
Node Number ◽  
Actual Measurement ◽  
Microwave Scattering ◽  
Contaminated Data ◽  
Along Track ◽  
Nearest Neighborhood ◽  
Sensitive Parameters ◽  
Ku Band

Rain affects the wind measurement accuracy of the Ku-band spaceborne scatterometer. In order to improve the quality of the retrieved wind field, it is necessary to identify and flag rain-contaminated data. In this study, an HY-2A scatterometer is used to study rain identification. In addition to the conventional parameters, such as the retrieved wind speed, the wind direction relative to the along-track direction, and the normalized beam difference, the experiment expands the mean deviation of the backscattering coefficient, the beam difference between fore and aft, and the node number of the wind vector cell (WVC) as the sensitive parameters according to the microwave scattering characteristics of rain and the actual measurement situation of the HY-2A. Furthermore, a rain identification model for HY2 (HY2RRM) with the K-Nearest Neighborhood (KNN) algorithm was built. After several tests, the accuracy of the selected HY2RRM approach is found to about 88%, and about 70% of rain-contaminated data can be accurately identified. The research results are helpful for better understanding the characteristics of microwave backscattering and provide a possible way to further improve the wind field retrieval accuracy of the HY-2A scatterometer and other Ku-band scatterometers.

scholarly journals Measuring ocean surface velocities with the KuROS and KaRADOC airborne near-nadir Doppler radars: a multi-scale analysis in preparation of the SKIM mission

2019 ◽  
Author(s):  
Louis Marié ◽  
Fabrice Collard ◽  
Frédéric Nouguier ◽  
Lucia Pineau-Guillou ◽  
Danièle Hauser ◽  
...  
Keyword(s):  
Wave Height ◽  
Theoretical Estimate ◽  
Phase Speed ◽  
Sea Surface ◽  
Doppler Velocity ◽  
Measured Velocity ◽  
Actual Measurement ◽  
Ka Band ◽  
Measurement Geometry ◽  
Ku Band

Abstract. Surface currents are poorly known over most of the oceans. Satellite-borne Doppler Waves and Current Scatterometers (DWCS) can be used to fill this observation gap. The Sea surface KInematics Multiscale (SKIM) proposal, is the first satellite concept built on a DWCS design at near-nadir angles, and now one of the two candidates to become the 9th mission of the European Space Agency Earth Explorer program. As part of the detailed design and feasibility studies (phase A) funded by ESA, airborne measurements were carried out with both a Ku-Band and a Ka-Band Doppler radars looking at the sea surface at near nadir-incidence in a real-aperture mode, i.e. in a geometry and mode similar to that of SKIM. The airborne radar KuROS was deployed to provide simultaneous measurements of the radar backscatter and Doppler velocity, in a side-looking configuration, with an horizontal resolution of about 5 to 10 m along the line of sight and integrated in the perpendicular direction over the real-aperture 1-way 3-dB footprint diameter (about 580 m). The KaRADOC system has a much narrower beam and footprint that only about 45 m in diameter. The experiment took place in November 2018 off the French Atlantic coast, with sea states representative of the open ocean and a well known tide-dominated current regime. The data set is analyzed to explore the contribution of non-geophysical velocities to the measurement and how the geophysical part of the measured velocity combines wave-resolved and wave-averaged scales. We find that the measured Doppler velocity contains a characteristic wave phase speed, called here C0 that is analogous to the Bragg phase speed of coastal High Frequency radars that use a grazing measurement geometry, with little variations ΔC associated to changes in sea state. The Ka-band measurements at an incidence of 12° are 10 % lower than the theoretical estimate C0 ~ 2.4 m/s for typical oceanic conditions defined by a wind speed of 7 m/s and a significant wave height of 2 m. For Ku-band the measured data is 30 % lower than the theoretical estimate 2.8 m/s. ΔC is of the order of 0.2 m/s for a 1 m change in wave height, and cannot be confused with a 1 m/s change in tidal current. The actual measurement of the current velocity from an aircraft at 4 to 18° incidence angle is, however, made difficult by uncertainties on the measurement geometry, which are much reduced in satellite measurements.

Sea surface current measurement with Ku-band SAR along-track interferometry

2011 ◽  
Author(s):  
Nobuo Kumagae ◽  
Kazuo Kawamura ◽  
Kenji Tatsumi ◽  
Masatada Furuhata ◽  
Masayoshi Tsuchida ◽  
...  
Keyword(s):  
Surface Current ◽  
Current Measurement ◽  
Sea Surface ◽  
Along Track ◽  
Ku Band

Measurement System of Contact Angle between Molten Steel Droplet and Refractory Material

2011 ◽  
Vol 299-300 ◽  
pp. 277-281
Author(s):  
Xiao Lin Qiu ◽  
Guo Wei Chang ◽  
Shu Ying Chen ◽  
Jian Guo He
Keyword(s):  
Contact Angle ◽  
Refractory Material ◽  
Molten Steel ◽  
Measurement System ◽  
Mean Deviation ◽  
Maximum Deviation ◽  
Actual Measurement ◽  
C Language ◽  
Computer Image Processing ◽  
Measurement Results

The distinct images of molten steel droplets were obtained utilizing a home-made experimental equipment, and the method which measures the contact angle between the molten steel droplet and the refractory material using a computer image processing technology and Visual C++ language was represented, meanwhile the measurement system of the contact angle was developed. The results show that the maximum deviation of the measurement system is 0.13° comparing with the actual measurement results, the minimum deviation is 0.03°, and the mean deviation is 0.06°. Under this experiment conditions, the contact angle increases 1.2° when the quality of sample increases from 0.2g to 0.8g at 1550°C, and the contact angle increases 2.3° when the temperature increases from 1550°C to 1600°C for the sample of 0.2g.

scholarly journals Horizontal geometry of trade-wind cumuli – aircraft observations from shortwave infrared imager versus radar profiler

2021 ◽  
Author(s):  
Henning Dorff ◽  
Heike Konow ◽  
Felix Ament
Keyword(s):  
High Resolution ◽  
Size Distribution ◽  
Wind Field ◽  
Trade Wind ◽  
Size Spectrum ◽  
Lower Sensitivity ◽  
Cumulus Clouds ◽  
Research Aircraft ◽  
Shortwave Infrared ◽  
Along Track

Abstract. This study elaborates how aircraft-based horizontal geometries of trade-wind cumulus clouds differ whether a one-dimensional (1D) profiler or a two-dimensional (2D) imager is used. While nadir profiling devices are limited to 1D realisation of the cloud transect size with limited representativeness of horizontal cloud extension, 2D imagers enhance our perspectives by mapping the horizontal cloud field. Both require high-resolution to detect the lower end of the cloud size spectrum. In this regard, the payload aboard the High Altitude and Long Range Research Aircraft (HALO) achieves a comparison and also a synergy of both measurement systems. Using the NARVAL-II campaign, we combine HALO observations from a 35.2 GHz cloud and precipitation radar (1D) and from the hyperspectral 2D imager specMACS, having a 30 times higher along-track resolution and compare their cloud masks. We examine cloud size distributions in terms of sensitivity to sample size, resolution and the considered field of view (2D or 1D). This specifies impacts on horizontal cloud sizes derived from the across-track perspective of the high-resolution imager in comparison to the radar curtain. We assess whether and how the trade-wind field amplifies uncertainties in cloud geometry observations along 1D transects through directional cloud elongation. Our findings reveal that each additional dimension, no matter of the device, causes a significant increase of observed clouds. The across-track field yields the highest increase in the cloud sample. The radar encounters difficulties to characterize the trade-wind cumuli size distribution. More than 60 % of clouds are subgrid scale for the radar. While the radar cannot resolve clouds shorter than 200 m and has a lower sensitivity, the amount of small invisible clouds leads to deviations in the size distribution. Double power law characteristics in the imager based cloud size distribution do not occur in radar observations. Along-track measurements do not necessarily cover the predominant cloud extent and inferred geometries lack of representativeness. Trade-wind cumuli show horizontal patterns similar to ellipses with a mean aspect ratio of 3 : 2. Instead of circular estimations based on the 1D transect, elliptic fits maintain the cloud area size distribution. Increasing wind speed tends to stretch clouds more and tilts them into the wind field, which makes transect measurements more representative along this axis.

scholarly journals Doppler radar wind field retrieval over the Po Valley

2006 ◽  
Vol 6 (2) ◽  
pp. 285-291
Author(s):  
Y. K. Goh ◽  
A. R. Holt ◽  
P. P. Alberoni
Keyword(s):  
Wind Field ◽  
Doppler Radar ◽  
Collaborative Study ◽  
Original Data ◽  
Wind Fields ◽  
Wind Model ◽  
Po Valley ◽  
Scanning Strategies ◽  
Along Track ◽  
Good Agreement

Abstract. Although methods of using multiple Doppler radars to study wind fields have long been proposed, and many research studies have been made, very few operational radar operators adopt methods which require the use of specific scanning strategies to allow the extraction of wind information. Here we report a collaborative study on dual-Doppler radars based on two Doppler radars in the Po valley, Italy. Unusually, the radars are only about 90 km apart, though operated by the same authority. The wind field syntheses are carried out on a 30 km by 30 km region where the two radars have overlapping scan coverage. An iterative method based on the linear wind model and the equation of mass continuity is used to construct the wind fields. The methodology has been validated by two different methods. The first method is to reconstruct the radial wind observed by each radar, and the second method is calculating and comparing the along-track component with that derived from the observations. Both two comparisons show good agreement with the original data.

Study on Synthesized Wind in the Numerical Simulation of Wind Waves

2014 ◽  
Vol 638-640 ◽  
pp. 1274-1279 ◽  
Author(s):  
Luo Bin Jin ◽  
Yuan Li ◽  
Lian Song Liang
Keyword(s):  
Tropical Cyclones ◽  
Wind Field ◽  
Wind Waves ◽  
Mean Deviation ◽  
Maximum Deviation ◽  
Wave Processes ◽  
Satellite Altimeter ◽  
Storm Wave ◽  
Simulation Results ◽  
Good Agreement

Numerical simulations are made for 10 storm wave processes during the period of 2008-2010, based on SWAN, with the Myers wind field, CCMP wind filed and the combination of the two as the storm driving wind field respectively. The results are compared with the observations from Jason-1 satellite altimeter during tropical cyclones (TCs). It indicates that Myers wind field makes a good agreement with measured values near the TC center, while CCMP wind field makes a good agreement with measured values far away from the TC center. Synthesis of the wind field combines the merit of the Myers wind field and CCMP wind field, and it is more in line with the wind field distribution; the simulation results of synthesized wind field make a good agreement with the measured results, with maximum deviation of -0.62m, mean deviation of -0.11m.

Guided surgery with 3D printed device: a case report

2020 ◽  
Author(s):  
Michelle Carvalho de Sales ◽  
Rafael Maluza Flores ◽  
Julianny da Silva Guimaraes ◽  
Gustavo Vargas da Silva Salomao ◽  
Tamara Kerber Tedesco ◽  
...  
Keyword(s):  
Operating Time ◽  
Three Dimensional ◽  
Conventional Technique ◽  
Cervical Region ◽  
Mean Deviation ◽  
Apical Region ◽  
Virtual Planning ◽  
Surgical Guide ◽  
Surgical Guides ◽  
High Level

Dental surgeons need in-depth knowledge of the bone tissue status and gingival morphology of atrophic maxillae. The aim of this study is to describe preoperative virtual planning of placement of five implants and to compare the plan with the actual surgical results. Three-dimensional planning of rehabilitation using software programs enables surgical guides to be specially designed for the implant site and manufactured using 3D printing. A patient with five teeth missing was selected for this study. The patient’s maxillary region was scanned with CBCT and a cast model was produced. After virtual planning using ImplantViewer, five implants were placed using a printed surgical guide. Two weeks after the surgical procedure, the patient underwent another CBCT scan of the maxilla. Statistically significant differences were detected between the virtually planned positions and the actual positions of the implants, with a mean deviation of 0.36 mm in the cervical region and 0.7 mm in the apical region. The surgical technique used enables more accurate procedures when compared to the conventional technique. Implants can be better positioned, with a high level of predictability, reducing both operating time and patient discomfort.

MicroVolt Variations of The Human Brain (Quantitative Electroencephalography) Display Differential Torque Effects During West-East versus North-South Orientation in the Geomagnetic Field

2016 ◽  
Vol 12 (2) ◽  
pp. 4255-4259
Author(s):  
Michael A Persinger ◽  
David A Vares ◽  
Paula L Corradini
Keyword(s):  
Human Brain ◽  
Geomagnetic Field ◽  
Neuronal Cell ◽  
Single Subject ◽  
Additional Energy ◽  
Actual Measurement ◽  
Neuronal Processes ◽  
Basic Physics ◽  
Order Of Magnitude ◽  
The Moment

                The human brain was assumed to be an elliptical electric dipole. Repeated quantitative electroencephalographic measurements over several weeks were completed for a single subject who sat in either a magnetic eastward or magnetic southward direction. The predicted potential difference equivalence for the torque while facing perpendicular (west-to-east) to the northward component of the geomagnetic field (relative to facing south) was 4 μV. The actual measurement was 10 μV. The oscillation frequency around the central equilibrium based upon the summed units of neuronal processes within the cerebral cortices for the moment of inertia was 1 to 2 ms which are the boundaries for the action potential of axons and the latencies for diffusion of neurotransmitters. The calculated additional energy available to each neuron within the human cerebrum during the torque condition was ~10-20 J which is the same order of magnitude as the energy associated with action potentials, resting membrane potentials, and ligand-receptor binding. It is also the basic energy at the level of the neuronal cell membrane that originates from gravitational forces upon a single cell and the local expression of the uniaxial magnetic anisotropic constant for ferritin which occurs in the brain. These results indicate that the more complex electrophysiological functions that are strongly correlated with cognitive and related human properties can be described by basic physics and may respond to specific geomagnetic spatial orientation.

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