scholarly journals A method for random uncertainties validation and probing the natural variability with application to TROPOMI/Sentinel5P total ozone measurements

2020 ◽  
Author(s):  
Viktoria F. Sofieva ◽  
Hei Shing Lee ◽  
Johanna Tamminen ◽  
Christophe Lerot ◽  
Fabian Romahn ◽  
...  
Keyword(s):  
Structure Function ◽  
Total Ozone ◽  
Random Noise ◽  
Separation Distance ◽  
Natural Variability ◽  
Measured Parameter ◽  
Inversion Algorithm ◽  
Temporal Separation ◽  
Spatio Temporal ◽  
Random Uncertainties

Abstract. In this paper, we discuss the method for validation of random uncertainties in the remote sensing measurements based on evaluation of the structure function, i.e., root-mean-square differences as a function of increasing spatio-temporal separation of the measurements. The limit at the zero mismatch provides the experimental estimate of random noise in the data. At the same time, this method allows probing the natural variability of the measured parameter. As an illustration, we applied this method to the clear-sky total ozone measurements by TROPOMI/Sentinel-5P. We found that the random uncertainties reported by the TROPOMI inversion algorithm, which are in the range 1–2 DU, agree well with the experimental uncertainty estimated by the structure function. Our analysis of the structure function has shown the expected results on total ozone variability: it is significantly smaller in the tropics compared to mid-latitudes. At mid-latitudes, ozone variability is much larger in winter than in summer. The ozone structure function is anisotropic (being larger in latitudinal direction) at horizontal scales larger than 10–20 km. The structure function rapidly grows with the separation distance. At mid-latitudes in winter, the ozone values can differ by 5 % at separations 300–500 km. The discussed method is a powerful tool in experimental estimates of the random noise in data and studies of natural variability and it can be used in various applications.

scholarly journals A method for random uncertainties validation and probing the natural variability with application to TROPOMI on board Sentinel-5P total ozone measurements

2021 ◽  
Vol 14 (4) ◽  
pp. 2993-3002
Author(s):  
Viktoria F. Sofieva ◽  
Hei Shing Lee ◽  
Johanna Tamminen ◽  
Christophe Lerot ◽  
Fabian Romahn ◽  
...  
Keyword(s):  
Structure Function ◽  
Total Ozone ◽  
Random Noise ◽  
Separation Distance ◽  
Natural Variability ◽  
Measured Parameter ◽  
Inversion Algorithm ◽  
Uncertainty Estimates ◽  
The Tropics ◽  
Random Uncertainties

Abstract. In this paper, we discuss the method for validation of random uncertainties in the remote sensing measurements based on evaluation of the structure function, i.e., root-mean-square differences as a function of increasing spatiotemporal separation of the measurements. The limit at the zero mismatch provides the experimental estimate of random noise in the data. At the same time, this method allows probing of the natural variability of the measured parameter. As an illustration, we applied this method to the clear-sky total ozone measurements by the TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel-5P satellite. We found that the random uncertainties reported by the TROPOMI inversion algorithm, which are in the range 1–2 DU, agree well with the experimental uncertainty estimates by the structure function. Our analysis of the structure function has shown the expected results on total ozone variability: it is significantly smaller in the tropics compared to mid-latitudes. At mid-latitudes, ozone variability is much larger in winter than in summer. The ozone structure function is anisotropic (being larger in the latitudinal direction) at horizontal scales larger than 10–20 km. The structure function rapidly grows with the separation distance. At mid-latitudes in winter, the ozone values can differ by 5 % at separations 300–500 km. The method discussed is a powerful tool in experimental estimates of the random noise in data and studies of natural variability, and it can be used in various applications.

Effect of background clutter on neural discrimination in the bat auditory midbrain

2021 ◽  
Author(s):  
Kathryne M Allen ◽  
Angeles Salles ◽  
Sanwook Park ◽  
Mounya Elhilali ◽  
Cynthia F. Moss
Keyword(s):  
Acoustic Scattering ◽  
Object Discrimination ◽  
Complex Environments ◽  
Acoustic Features ◽  
Temporal Separation ◽  
Complex Sounds ◽  
Electrophysiological Recordings ◽  
Background Clutter ◽  
Spatio Temporal ◽  
Neural Underpinnings

The discrimination of complex sounds is a fundamental function of the auditory system. This operation must be robust in the presence of noise and acoustic clutter. Echolocating bats are auditory specialists that discriminate sonar objects in acoustically complex environments. Bats produce brief signals, interrupted by periods of silence, rendering echo snapshots of sonar objects. Sonar object discrimination requires that bats process spatially and temporally overlapping echoes to make split-second decisions. The mechanisms that enable this discrimination are not well understood, particularly in complex environments. We explored the neural underpinnings of sonar object discrimination in the presence of acoustic scattering caused by physical clutter. We performed electrophysiological recordings in the inferior colliculus of awake big brown bats, to broadcasts of pre-recorded echoes from physical objects. We acquired single unit responses to echoes and discovered a sub-population of IC neurons that encode acoustic features that can be used to discriminate between sonar objects. We further investigated the effects of environmental clutter on this population's encoding of acoustic features. We discovered that the effect of background clutter on sonar object discrimination is highly variable and depends on object properties and target-clutter spatio-temporal separation. In many conditions, clutter impaired discrimination of sonar objects. However, in some instances clutter enhanced acoustic features of echo returns, enabling higher levels of discrimination. This finding suggests that environmental clutter may augment acoustic cues used for sonar target discrimination and provides further evidence in a growing body of literature that noise is not universally detrimental to sensory encoding.

scholarly journals The Observational Error of Automated Wind Reports from Aircraft

1986 ◽  
Vol 67 (2) ◽  
pp. 177-185 ◽  
Author(s):  
Lauren L. Morone
Keyword(s):  
Measurement Error ◽  
Structure Function ◽  
Error Variance ◽  
Structure Functions ◽  
Separation Distance ◽  
Observational Error ◽  
Random Measurement Error ◽  
Measurement Error Variance ◽  
Flight Level ◽  
Types Of Error

Data collected from aircraft equipped with AIDS (Aircraft Integrated Data System) instrumentation during the Global Weather Experiment year of 1979 are used to estimate the observational error of winds at flight level from this and other aircraft automated wind-reporting systems. Structure functions are computed from reports that are paired using specific criteria. The value of this function extrapolated to zero separation distance is an estimate of twice the random measurement-error variance of the AIDS-measured winds. Component-wind errors computed in this way range from 2.1 to 3.1 m · s−1 for the two months of data examined, January and August 1979. Observational error, specified in optimum-interpolation analyses to allow the analysis to distinguish among observations of differing quality, is composed of both measurement error and the error of unrepresentativeness. The latter type of error is a function of the resolvable scale of the analysis-prediction system. The structure function, which measures the variability of a field as a function of separation distance, includes both of these types of error. If the resolvable scale of an analysis procedure is known, an estimate of the observational error can be computed from the structure function at that particular distance. An observational error of 5.3 m · s−1 was computed for the u and v wind components for a sample resolvable scale of 300 km. The errors computed from the structure functions are compared to colocation statistics from radiosondes. The errors associated with automated wind reports are found to compare favorably with those estimated for radiosonde winds at that level.

scholarly journals Analysis of her1 and her7 Mutants Reveals a Spatio Temporal Separation of the Somite Clock Module

PLoS ONE ◽  
2012 ◽  
Vol 7 (6) ◽  
pp. e39073 ◽  
Author(s):  
Suma Choorapoikayil ◽  
Bernd Willems ◽  
Peter Ströhle ◽  
Martin Gajewski
Keyword(s):  
Temporal Separation ◽  
Spatio Temporal ◽  
Clock Module

Control of Growth and Morphology of a Crystal Surface by Induced Spatio-Temporal Oscillations of Surface Temperature

2006 ◽  
Vol 960 ◽  
Author(s):  
Mikhail Khenner
Keyword(s):  
Crystal Surface ◽  
Wave Length ◽  
Temporal Variations ◽  
Separation Distance ◽  
Spatiotemporal Chaos ◽  
Cold Regions ◽  
Stable Case ◽  
Interference Fringes ◽  
Spatio Temporal ◽  
Diffusion Mass

ABSTRACTThis paper presents the model for pattern formation in the course of thermodynamically stable and unstable crystal growth from vapor phase, which is influenced by rapid spatio-temporal variations of substrate and film temperature. In the model, such variations result from the interference heating of a substrate by weak pulsed laser beams. In the thermodynamically stable case the surface relaxational dynamics is influenced by surface diffusion mass transport from hot to cold regions of a substrate; this leads to accumulation of mass in cold regions and depletion in hot regions. In the thermodynamically unstable case the underlying faceting (spinodal) instability coupled to diffusion mass fluxes from hot to cold regions leads to formation of pyramidal surface structures. The scale of stationary coarsened structure increases as the separation distance of the adjacent interference fringes decreases (relative to the intrinsic faceting wave length, which is determined by the balance between the corner regularization energies and the surface energy anisotropy). On the other hand, the coarsening rates decrease with decreasing the separation distance, at least at particular typical deposition strength. The deposition strength and the separation distance of the interference fringes determine the transient and stationary pattern shape. By effectively redistributing adatoms on a substrate through the enhanced, spatially inhomogeneous diffusion, the interference heating mechanism delays, for large separation distances, the onset of spatiotemporal chaos as the growth rate increases.

Evaluating the ecological effects of Mediterranean marine protected areas: habitat, scale and the natural variability of ecosystems

2000 ◽  
Vol 27 (2) ◽  
pp. 159-178 ◽  
Author(s):  
J.A. GARCÍA CHARTON ◽  
I.D. WILLIAMS ◽  
A. PÉREZ RUZAFA ◽  
M. MILAZZO ◽  
R. CHEMELLO ◽  
...  
Keyword(s):  
Protected Areas ◽  
Marine Protected Areas ◽  
Multiple Scales ◽  
Natural Variability ◽  
Data Sets ◽  
Nested Designs ◽  
Spatio Temporal ◽  
Habitat Scale ◽  
Physical Elements

The capability to detect and predict the responses of marine populations and communities to the establishment of marine protected areas (MPAs) depends on the ability to distinguish between the influences of management and natural variability due to the effects of factors other than protection. Thus, it is important to understand and quantify the magnitude and range of this natural variability at each scale of observation. Here we review the scale of responses of target populations and communities to protection within Mediterranean MPAs, against their ‘normal’ spatio-temporal heterogeneity, and compare those with documented cases from other temperate and tropical marine ecosystems. Additionally, we approach the problem of the relative importance of habitat structure, considered as a set of biological and physical elements of the seascape hierarchically arranged in space at multiple scales, to drive natural variability. We conclude that much more effort has to be made to characterize heterogeneity in relation to Mediterranean MPAs, and to quantify and explain relationships between target species and their habitats as sources of such variability. These studies should be based on sound sampling designs, which (1) generate long-term data sets, and would ideally (2) be based on a Mediterranean-wide comparison of a number of protected and unprotected localities, (3) be designed from a multi-scaled perspective, and (4) control for factors other than protection, in order to avoid their confounding effects. The need for appropriate spatial and temporal replication, nested designs and power analysis is advocated.

Vortex merger in rotating stratified flows

2002 ◽  
Vol 455 ◽  
pp. 83-101 ◽  
Author(s):  
DAVID G. DRITSCHEL
Keyword(s):  
Aspect Ratio ◽  
Initial Conditions ◽  
Random Noise ◽  
Three Dimensional ◽  
Separation Distance ◽  
Two Dimensional ◽  
Initial Separation ◽  
Weak Exchange ◽  
First Results ◽  
Asymmetric Vortices

This paper describes the interaction of symmetric vortices in a three-dimensional quasi-geostrophic fluid. The initial vortices are taken to be uniform-potential-vorticity ellipsoids, of height 2h and width 2R, and with centres at (±d/2; 0, 0), embedded within a background flow having constant background rotational and buoyancy frequencies, f/2 and N respectively. This problem was previously studied by von Hardenburg et al. (2000), who determined the dimensionless critical merger distance d/R as a function of the height-to-width aspect ratio h/R (scaled by f/N). Their study, however, was limited to small to moderate values of h/R, as it was anticipated that merger at large h/R would reduce to that for two columnar two-dimensional vortices, i.e. d/R ≈ 3.31. Here, it is shown that no such two-dimensional limit exists; merger is found to occur at any aspect ratio, with d ∼ h for h/R [Gt ] 1.New results are also found for small to moderate values of h/R. In particular, our numerical simulations reveal that asymmetric merger is predominant, despite the initial conditions, if one includes a small amount of random noise. For small to moderate h/R, decreasing the initial separation distance d first results in a weak exchange of material, with one vortex growing at the expense of the other. As d decreases further, this exchange increases and leads to two dominant but strongly asymmetric vortices. Finally, for yet smaller d, rapid merger into a single dominant vortex occurs – in effect the initial vortices exchange nearly all of their material with one another in a nearly symmetrical fashion.

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