scholarly journals The ESA Permanent Facility for Altimetry Calibration: Monitoring Performance of Radar Altimeters for Sentinel-3A, Sentinel-3B and Jason-3 Using Transponder and Sea-Surface Calibrations with FRM Standards

2020 ◽  
Vol 12 (16) ◽  
pp. 2642
Author(s):  
Stelios Mertikas ◽  
Achilleas Tripolitsiotis ◽  
Craig Donlon ◽  
Constantin Mavrocordatos ◽  
Pierre Féménias ◽  
...  
Keyword(s):  
Objective Assessment ◽  
Ground Truth ◽  
Sea Surface ◽  
Crossover Analysis ◽  
Operational Phase ◽  
The Stability ◽  
Independent Calibration ◽  
Monitoring Performance

This work presents the latest calibration results for the Copernicus Sentinel-3A and -3B and the Jason-3 radar altimeters as determined by the Permanent Facility for Altimetry Calibration (PFAC) in west Crete, Greece. Radar altimeters are used to provide operational measurements for sea surface height, significant wave height and wind speed over oceans. To maintain Fiducial Reference Measurement (FRM) status, the stability and quality of altimetry products need to be continuously monitored throughout the operational phase of each altimeter. External and independent calibration and validation facilities provide an objective assessment of the altimeter’s performance by comparing satellite observations with ground-truth and in-situ measurements and infrastructures. Three independent methods are employed in the PFAC: Range calibration using a transponder, sea-surface calibration relying upon sea-surface Cal/Val sites, and crossover analysis. Procedures to determine FRM uncertainties for Cal/Val results have been demonstrated for each calibration. Biases for Sentinel-3A Passes No. 14, 278 and 335, Sentinel-3B Passes No. 14, 71 and 335, as well as for Jason-3 Passes No. 18 and No. 109 are given. Diverse calibration results by various techniques, infrastructure and settings are presented. Finally, upgrades to the PFAC in support of the Copernicus Sentinel-6 ‘Michael Freilich’, due to launch in November 2020, are summarized.

scholarly journals High temperature structural study of decagonal Al-Cu-Rh quasicrystal.

2014 ◽  
Vol 70 (a1) ◽  
pp. C94-C94
Author(s):  
Pawel Kuczera ◽  
Walter Steurer
Keyword(s):  
Structural Changes ◽  
Configurational Entropy ◽  
Lattice Vibrations ◽  
X Ray Diffraction ◽  
Stabilization Mechanism ◽  
X Ray ◽  
Comparative Structure ◽  
The Stability

The structure of d(ecagonal)-Al-Cu-Rh has been studied as a function of temperature by in-situ single-crystal X-ray diffraction in order to contribute to the discussion on energy or entropy stabilization of quasicrystals (QC) [1]. The experiments were performed at 293 K, 1223 K, 1153 K, 1083 K, and 1013 K. A common subset of 1460 unique reflections was used for the comparative structure refinements at each temperature. The results obtained for the HT structure refinements of d-Al-Cu-Rh QC seem to contradict a pure phasonic-entropy-based stabilization mechanism [2] for this QC. The trends observed for the ln func(I(T1 )/I(T2 )) vs.|k⊥ |^2 plots indicate that the best on-average quasiperiodic order exists between 1083 K and 1153 K, however, what that actually means is unclear. It could indicate towards a small phasonic contribution to entropy, but such contribution is not seen in the structure refinements. A rough estimation of the hypothetic phason instability temperature shows that it would be kinetically inaccessible and thus the phase transition to a 12 Å low T structure (at ~800 K) is most likely not phason-driven. Except for the obvious increase in the amplitude of the thermal motion, no other significant structural changes, in particular no sources of additional phason-related configurational entropy, were found. All structures are refined to very similar R-values, which proves that the quality of the refinement at each temperature is the same. This suggests, that concerning the stability factors, some QCs could be similar to other HT complex intermetallic phases. The experimental results clearly show that at least the ~4 Å structure of d-Al-Cu-Rh is a HT phase therefore entropy plays an important role in its stabilisation mechanism lowering the free energy. However, the main source of this entropy is probably not related to phason flips, but rather to lattice vibrations, occupational disorder unrelated to phason flips like split positions along the periodic axis.

scholarly journals Determination of sea surface height from moving ships with dynamic corrections

2012 ◽  
Vol 2 (3) ◽  
pp. 172-187 ◽  
Author(s):  
J. Reinking ◽  
A. Härting ◽  
L. Bastos
Keyword(s):  
Satellite System ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
Sea Surface Heights ◽  
Positioning Analysis ◽  
Remote Sensing Techniques ◽  
Global Navigation Satellite

AbstractWith the growing global efforts to estimate the influence of civilization on the climate change it would be desirable to survey sea surface heights (SSH) not only by remote sensing techniques like satellite altimetry or (GNSS) Global Navigation Satellite System reflectometry but also by direct and in-situ measurements in the open ocean. In recent years different groups attempted to determine SSH by ship-based GNSS observations. Due to recent advances in kinematic GNSS (PPP) Precise Point Positioning analysis it is already possible to derive GNSS antenna heights with a quality of a few centimeters. Therefore it is foreseeable that this technique will be used more intensively in the future, with obvious advantages in sea positioning. For the determination of actual SSH from GNSS-derived antenna heights aboard seagoing vessels some essential hydrostatic and hydrodynamic corrections must be considered in addition to ocean dynamics and related corrections. Systematic influences of ship dynamics were intensively analyzed and sophisticated techniques were developed at the Jade University during the last decades to precisely estimate mandatory corrections. In this paper we will describe the required analyses and demonstrate their application by presenting a case study from an experiment on a cruise vessel carried out in March 2011 in the Atlantic Ocean.

Spatial Representativeness Analysis for Snow Depth Measurements of Meteorological Stations in Northeast China

2020 ◽  
Vol 21 (4) ◽  
pp. 791-805
Author(s):  
Yuanyuan Wang ◽  
Zhaojun Zheng
Keyword(s):  
Snow Depth ◽  
Northeast China ◽  
Ground Truth ◽  
Snow Accumulation ◽  
Point Scale ◽  
Coarse Scale ◽  
Study Region ◽  
Performance Metric

AbstractTriple collocation (TC) is a popular technique for determining the data quality of three products that estimate the same geophysical variable using mutually independent methods. When TC is applied to a triplet of one point-scale in situ and two coarse-scale datasets that have the similar spatial resolution, the TC-derived performance metric for the point-scale dataset can be used to assess its spatial representativeness. In this study, the spatial representativeness of in situ snow depth measurements from the meteorological stations in northeast China was assessed using an unbiased correlation metric estimated with TC. Stations are considered representative if ; that is, in situ measurements explain no less than 50% of the variations in the “ground truth” of the snow depth averaged at the coarse scale (0.25°). The results confirmed that TC can be used to reliably exploit existing sparse snow depth networks. The main findings are as follows. 1) Among all the 98 stations in the study region, 86 stations have valid values, of which 57 stations are representative for the entire snow season (October–December, January–April). 2) Seasonal variations in are large: 63 stations are representative during the snow accumulation period (December–February), whereas only 25 stations are representative during the snow ablation period (October–November, March–April). 3) The is positively correlated with mean snow depth, which largely determines the global decreasing trend in from north to south. After removing this trend, residuals in can be explained by heterogeneity features concerning elevation and conditional probability of snow presence near the stations.

scholarly journals Postural Control in Female Rhythmic Gymnasts in Selected Balance Exercises: A Study of Two Cases

2019 ◽  
Vol 26 (1) ◽  
pp. 3-7 ◽  
Author(s):  
Małgorzata Sobera ◽  
Alicja Rutkowska-Kucharska
Keyword(s):  
Postural Control ◽  
Objective Assessment ◽  
Training Experience ◽  
Lateral Direction ◽  
Balance Exercises ◽  
The Stability ◽  
And Training ◽  
Rhythmic Gymnasts ◽  
Anterior Posterior

AbstractIntroduction. The aim of the study was to determine the differences in the quality of postural control between two female rhythmic gymnasts with different training experience during the performance of balance exercises. In rhythmic gymnastics, the same balance exercises are performed by novice and elite gymnasts. Balance exercises involving standing on the toes of one leg with the free leg raised in different positions are considered to be extreme forms of exercise in terms of the postural balance abilities required. In coaching practice, it is important to have tools which facilitate the objective assessment of the process of maintaining balance in such exercises.Material and methods.The study involved two female rhythmic gymnasts: a younger one (age = 8 years and training experience = 4 years) and an older one (age = 21 years and training experience = 14 years). The athletes performed three balance exercises standing on a Kistler platform: the split with hand support (lateral balance), the ring with hand support, and the back split without hand support (balance on the whole foot). The parameters describing the quality of postural control used in the current analysis were the range and velocity of COP displacements in the anterior-posterior and medial-lateral directions.Results. Postural control in the balance exercises in the younger rhythmic gymnast was characterised by almost two times greater COP displacements in the anterior-posterior direction and more rapid than that of the older gymnast. COP displacements in the medial-lateral direction in all the exercises described did not differentiate the subjects. In the back split without hand support, the older athlete showed greater variability of postural control with smaller COP displacement and velocity than the younger gymnast.Conclusion. Gymnastics training should include exercises strengthening the muscles acting on the ankle and hip joints, which could improve the stability of these joints during the performance of difficult balance exercises. Improving the stabilising function of these muscles helps to minimise anterior-posterior movements in these joints.

scholarly journals Colletotrichum Gloesporioides Inhibition In Situ by Chitosan-Ruta graveolens Essential Oil Coatings: Effect on Microbiological, Physicochemical, and Organoleptic Properties of Guava (Psidium guajava L.) during Room Temperature Storage

Biomolecules ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 399 ◽  
Author(s):  
Carlos David Grande Tovar ◽  
Johannes Delgado-Ospina ◽  
Diana Paola Navia Porras ◽  
Yeimmy Peralta-Ruiz ◽  
Alexander Pérez Cordero ◽  
...  
Keyword(s):  
Essential Oil ◽  
Microbiological Quality ◽  
Pathogenic Fungi ◽  
Psidium Guajava ◽  
Ruta Graveolens ◽  
In Situ Investigation ◽  
The Stability ◽  
Temperature Storage

Guava is a fruit appreciated worldwide for its high content of bioactive compounds. However, it is considered a highly perishable fruit, generally attacked by pathogenic species such as the fungi Colletotrichum gloeosporioides, which causes anthracnosis. To diminish the losses caused by pathogenic fungi, coatings of chitosan (CS) with Ruta graveolens essential oil (RGEO) in different concentrations (0.5, 1.0, 1.5% v/v) were applied in situ and their effects on the physical properties and microbiological quality of the guavas were studied. The CS+RGEO coated fruits exhibited better physicochemical behavior and lower microbiological decay as compared to the uncoated guavas, demonstrating the effectiveness of the coatings, especially those with 1.5% of RGEO content. All the fruits coated had greater acceptance and quality than the controls, being more those with essential oil incorporation. In situ investigation of C. gloesporioides infection of guavas demonstrated that the CS+RGEO coated guavas showed a high percentage of inhibition in the development of anthracnose lesions. In the present investigation, an alternative method has been proposed to extend the stability of the guavas fruit up to 12 days with application in the food industry.

scholarly journals Sea Surface Salinity Seasonal Variability in the Tropics from Satellites, Gridded In Situ Products and Mooring Observations

2020 ◽  
Vol 13 (1) ◽  
pp. 110
Author(s):  
Frederick M. Bingham ◽  
Susannah Brodnitz ◽  
Lisan Yu
Keyword(s):  
Seasonal Variability ◽  
Ground Truth ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Surface Salinity ◽  
Zero Bias ◽  
In Situ Data ◽  
The Tropics ◽  
Good Agreement

Satellite observations of sea surface salinity (SSS) have been validated in a number of instances using different forms of in situ data, including Argo floats, moorings and gridded in situ products. Since one of the most energetic time scales of variability of SSS is seasonal, it is important to know if satellites and gridded in situ products are observing the seasonal variability correctly. In this study we validate the seasonal SSS from satellite and gridded in situ products using observations from moorings in the global tropical moored buoy array. We utilize six different satellite products, and two different gridded in situ products. For each product we have computed seasonal harmonics, including amplitude, phase and fraction of variance (R2). These quantities are mapped for each product and for the moorings. We also do comparisons of amplitude, phase and R2 between moorings and all the satellite and gridded in situ products. Taking the mooring observations as ground truth, we find general good agreement between them and the satellite and gridded in situ products, with near zero bias in phase and amplitude and small root mean square differences. Tables are presented with these quantities for each product quantifying the degree of agreement.

scholarly journals Comparison of In Situ and Satellite-Derived Sea Surface Temperatures in the Gulf of Carpentaria

2007 ◽  
Vol 24 (10) ◽  
pp. 1773-1784 ◽  
Author(s):  
Ian J. Barton
Keyword(s):  
Single Channel ◽  
Pilot Project ◽  
Sea Surface ◽  
Global Ocean ◽  
Satellite Measurements ◽  
Ocean Data Assimilation ◽  
Infrared Radiometer

Abstract During 30 days in May and June 2003, the R/V Southern Surveyor was operating in the Gulf of Carpentaria, northern Australia. Measurements of sea surface temperature (SST) were made with an accurate single-channel infrared radiometer as well as with the ship’s thermosalinograph. These ship-based measurements have been used to assess the quality of the SST derived from nine satellite-borne instruments. The satellite dataset compiled during this period also allows the intercomparison of satellite-derived SST fields in areas not covered by the ship’s track. An assessment of the SST quality from each satellite instrument is presented, and suggestions for blending ground and satellite measurements into a single product are made. These suggestions are directly applicable to the international Global Ocean Data Assimilation Experiment (GODAE) High Resolution SST Pilot Project (GHRSST-PP) that is currently developing an operational system to provide 6-hourly global fields of SST at a spatial resolution close to 10 km. The paper demonstrates how the Diagnostic Datasets (DDSs) and Matchup Database (MDB) of the GHRSST-PP can be used to monitor the quality of individual and blended SST datasets. Recommendations for future satellite missions that are critical to the long-term generation of accurate blended SST datasets are included.

scholarly journals Surface Pressure Tide Climatologies Deduced from a Quality-Controlled Network of Barometric Observations*

2014 ◽  
Vol 142 (12) ◽  
pp. 4872-4889 ◽  
Author(s):  
Michael Schindelegger ◽  
Richard D. Ray
Keyword(s):  
Surface Pressure ◽  
Global Analysis ◽  
Ground Truth ◽  
Fine Mesh ◽  
Control Framework ◽  
Spatial Coverage ◽  
Analysis Models

Abstract Global “ground truth” knowledge of solar diurnal S1 and semidiurnal S2 surface pressure tides as furnished by barometric in situ observations represents a valuable standard for wide-ranging geophysical and meteorological applications. This study attempts to aid validations of the air pressure tide signature in current climate or atmospheric analysis models by developing a new global assembly of nearly 6900 mean annual S1 and S2 estimates on the basis of station and marine barometric reports from the International Surface Pressure Databank, version 2 (ISPDv2), for a principal time span of 1990–2010. Previously published tidal compilations have been limited by inadequate spatial coverage or by internal inconsistencies and outliers from suspect tidal analyses; here, these problems are mostly overcome through 1) automated data filtering under ISPDv2’s quality-control framework and 2) a meticulously conducted visual inspection of station harmonic decompositions. The quality of the resulting compilation is sufficient to support global interpolation onto a reasonably fine mesh of 1° horizontal spacing. A multiquadric interpolation algorithm, with parameters fine-tuned by frequency and for land or ocean regions, is employed. Global charts of the gridded surface pressure climatologies are presented, and these are mapped to a wavenumber versus latitude spectrum for comparison with long-term means of S1 and S2 from four present-day atmospheric analysis systems. This cross verification, shown to be feasible even for the minor stationary modes of the tides, reveals a small but probably significant overestimation of up to 18% for peak semidiurnal amplitudes as predicted by global analysis models.

Modeling of Growth of Lactobacillus sanfranciscensis and Candida milleri in Response to Process Parameters of Sourdough Fermentation

1998 ◽  
Vol 64 (7) ◽  
pp. 2616-2623 ◽  
Author(s):  
Michael G. Gänzle ◽  
Michaela Ehmann ◽  
Walter P. Hammes
Keyword(s):  
Acetic Acid ◽  
Biological Significance ◽  
Ecological Factors ◽  
Lactobacillus Sanfranciscensis ◽  
Inhibition Of Growth ◽  
The Stability ◽  
Ph Range

ABSTRACT We investigated the effect of the ecological factors pH, temperature, ionic strength, and lactate, acetate, and ethanol levels on Candida milleri and two strains of Lactobacillus sanfranciscensis, organisms representative of the microflora of sourdough. A mathematical model describing the single and combined effects of these factors on the growth of these organisms was established in accordance with the following criteria: quality of fit, biological significance of the parameters, and applicability of the in vitro data to in situ processes. The growth rates of L. sanfranciscensis LTH1729 and LTH2581 were virtually identical under all conditions tested. These organisms tolerated >160 mmol of undissociated acetic acid per liter. Growth occurred in the pH range of 3.9 to 6.7 and was completely inhibited by 4% NaCl. C. milleri had a lower optimum temperature for growth (27°C) than the lactobacilli. The growth of the yeast was not affected by pH in the range of 3.5 to 7, and up to 8% NaCl was tolerated. Complete inhibition of growth occurred at 150 mmol of undissociated acetic acid per liter, but acetate at concentrations of up to 250 mmol/liter exerted virtually no effect. The model provides insight into factors contributing to the stability of the sourdough microflora and can facilitate the design of novel sourdough processes.

scholarly journals In situ SST Quality Monitor (iQuam)

2014 ◽  
Vol 31 (1) ◽  
pp. 164-180 ◽  
Author(s):  
Feng Xu ◽  
Alexander Ignatov
Keyword(s):  
Time Series ◽  
Sea Surface ◽  
Current Status ◽  
Web Page ◽  
Telecommunication System ◽  
Calibration And Validation ◽  
Global Telecommunication System ◽  
The Web

Abstract The quality of in situ sea surface temperatures (SSTs) is critical for calibration and validation of satellite SSTs. In situ SSTs come from different countries, agencies, and platforms. As a result, their quality is often suboptimal, nonuniform, and measurement-type specific. This paper describes a system developed at the National Oceanic and Atmospheric Administration (NOAA), the in situ SST Quality Monitor (iQuam; www.star.nesdis.noaa.gov/sod/sst/iquam/). It performs three major functions with the Global Telecommunication System (GTS) data: 1) quality controls (QC) in situ SSTs, using Bayesian reference and buddy checks similar to those adopted in the Met Office, in addition to providing basic screenings, such as duplicate removal, plausibility, platform track, and SST spike checks; 2) monitors quality-controlled SSTs online, in near–real time; and 3) serves reformatted GTS SST data to NOAA and external users with quality flags appended. Currently, iQuam’s web page displays global monthly maps of measurement locations stratified by four in situ platform types (drifters, ships, and tropical and coastal moorings) as well as their corresponding “in situ minus reference” SST statistics. Time series of all corresponding SST and QC statistics are also trended. The web page user can also monitor individual in situ platforms. The current status of iQuam and ongoing improvements are discussed.

Sign in / Sign up

Export Citation Format

Share Document