scholarly journals Estimation of Near-Ground Propagation Conditions Using Radar Ground Echo Coverage

2011 ◽  
Vol 28 (2) ◽  
pp. 165-180 ◽  
Author(s):  
Shinju Park ◽  
Frédéric Fabry
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
Vertical Gradient ◽  
Simple Method ◽  
Radar Observations ◽  
Beam Bending ◽  
Radar Measurements ◽  
Temporal And Spatial ◽  
Ground Echoes

Abstract The vertical gradient of refractivity (dN/dh) determines the path of the radar beam; namely, the larger the negative values of the refractivity gradient, the more the beam bends toward the ground. The variability of the propagation conditions significantly affects the coverage of the ground echoes and, thus, the quality of the scanning radar measurements. The information about the vertical gradient of refractivity is usually obtained from radiosonde soundings whose use, however, is limited by their coarse temporal and spatial resolution. Because radar ground echo coverage provides clues about how severe the beam bending can be, we have investigated a method that uses radar observations to infer propagation conditions with better temporal resolution than the usual soundings. Using the data collected during the International H2O Project (IHOP_2002), this simple method has shown some skill in capturing the propagation conditions similar to these estimated from soundings. However, the evaluation of the method has been challenging because of 1) the limited resolution of the conventional soundings in time and space, 2) the lack of other sources of data with which to compare the results, and 3) the ambiguity in the separation of ground from weather echoes.

scholarly journals Sensitivity of hydrological models to temporal and spatial resolutions of rainfall data

2019 ◽  
Vol 23 (6) ◽  
pp. 2647-2663 ◽  
Author(s):  
Yingchun Huang ◽  
András Bárdossy ◽  
Ke Zhang
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
Model Performance ◽  
Daily Rainfall ◽  
High Temporal Resolution ◽  
Dense Network ◽  
Spatially Distributed ◽  
Important Input ◽  
Temporal And Spatial ◽  
Improved Model

Abstract. Rainfall is the most important input for rainfall–runoff models. It is usually measured at specific sites on a daily or sub-daily timescale and requires interpolation for further application. This study aims to evaluate whether a higher temporal and spatial resolution of rainfall can lead to improved model performance. Four different gridded hourly and daily rainfall datasets with a spatial resolution of 1 km × 1 km for the state of Baden-Württemberg in Germany were constructed using a combination of data from a dense network of daily rainfall stations and a less dense network of sub-daily stations. Lumped and spatially distributed HBV models were used to investigate the sensitivity of model performance to the spatial resolution of rainfall. The four different rainfall datasets were used to drive both lumped and distributed HBV models to simulate daily discharges in four catchments. The main findings include that (1) a higher temporal resolution of rainfall improves the model performance if the station density is high; (2) a combination of observed high temporal resolution observations with disaggregated daily rainfall leads to further improvement in the tested models; and (3) for the present research, the increase in spatial resolution improves the performance of the model insubstantially or only marginally in most of the study catchments.

scholarly journals Soil moisture mapping over West Africa with a 30-min temporal resolution using AMSR-E observations and a satellite-based rainfall product

2009 ◽  
Vol 13 (10) ◽  
pp. 1887-1896 ◽  
Author(s):  
T. Pellarin ◽  
T. Tran ◽  
J.-M. Cohard ◽  
S. Galle ◽  
J.-P. Laurent ◽  
...  
Keyword(s):  
Soil Moisture ◽  
West Africa ◽  
Spatial Resolution ◽  
Temporal Resolution ◽  
Microwave Emission ◽  
Emission Model ◽  
Rainfall Estimation ◽  
Simple Method ◽  
Antecedent Precipitation ◽  
The Difference

Abstract. An original and simple method to map surface soil moisture over large areas has been developed to obtain data with a high temporal and spatial resolution for the study of possible feedback mechanisms between soil moisture and convection in West Africa. A rainfall estimation product based on Meteosat geostationary satellite measurements is first used together with a simple Antecedent Precipitation Index (API) model to produce soil moisture maps at a spatial resolution of 10×10 km2 and a temporal resolution of 30-min. However, given the uncertainty of the satellite-based rainfall estimation product, the resulting soil moisture maps are not sufficiently accurate. For this reason, a technique based on assimilating AMSR-E C-band measurements into a microwave emission model was developed in which the estimated rainfall rates between two successive AMSR-E brightness temperature (TB) measurements are adjusted by multiplying them by a factor between 0 and 7 that minimizes the difference between simulated and observed TBs. Ground-based soil moisture measurements obtained at three sites in Niger, Mali and Benin were used to assess the method which was found to improve the soil moisture estimates on all three sites.

scholarly journals Achieving high spatial and temporal resolution with perfusion MRI in the head and neck region using golden-angle radial sampling

2020 ◽  
Author(s):  
Andrea Tomppert ◽  
Wolfgang Wuest ◽  
Marco Wiesmueller ◽  
Rafael Heiss ◽  
Markus Kopp ◽  
...  
Keyword(s):  
Image Quality ◽  
Head And Neck ◽  
Spatial Resolution ◽  
Temporal Resolution ◽  
Neck Region ◽  
Head And Neck Region ◽  
Golden Angle ◽  
Edge Sharpness ◽  
Temporal And Spatial ◽  
Golden Angle Radial

Abstract Objectives Conventional perfusion-weighted MRI sequences often provide poor spatial or temporal resolution. We aimed to overcome this problem in head and neck protocols using a golden-angle radial sparse parallel (GRASP) sequence. Methods We prospectively included 58 patients for examination on a 3.0-T MRI using a study protocol. GRASP (A) was applied to a volumetric interpolated breath-hold examination (VIBE) with 135 reconstructed pictures and high temporal (2.5 s) and spatial resolution (0.94 × 0.94 × 3.00 mm). Additional sequences of matching temporal resolution (B: 2.5 s, 1.88 × 1.88 × 3.00 mm), with a compromise between temporal and spatial resolution (C: 7.0 s, 1.30 × 1.30 × 3.00 mm) and with matching spatial resolution (D: 145 s, 0.94 × 0.94 × 3.00 mm), were subsequently without GRASP. Instant inline-image reconstructions (E) provided one additional series of averaged contrast information throughout the entire acquisition duration of A. Overall diagnostic image quality, edge sharpness and contrast of soft tissues, vessels and lesions were subjectively rated using 5-point Likert scales. Objective image quality was measured as contrast-to-noise ratio in D and E. Results Overall, the anatomic and pathologic image quality was substantially better with the GRASP sequence for the temporally (A/B/C, all p < 0.001) and spatially resolved comparisons (D/E, all p < 0.002 except lesion edge sharpness with p = 0.291). Image artefacts were also less likely to occur with GRASP. Differences in motion, aliasing and truncation were mainly significant, but pulsation and fat suppression were comparable. In addition, the contrast-to-noise ratio of E was significantly better than that of D (pD-E < 0.001). Conclusions High temporal and spatial resolution can be obtained synchronously using a GRASP-VIBE technique for perfusion evaluation in head and neck MRI. Key Points • Golden-angle radial sparse parallel (GRASP) sampling allows for temporally resolved dynamic acquisitions with a very high image quality. • Very low-contrast structures in the head and neck region can benefit from using the GRASP sequence. • Inline-image reconstruction of dynamic and static series from one single acquisition can replace the conventional combination of two acquisitions, thereby saving examination time.

scholarly journals Sensitivity of hydrological model to the temporal and spatial resolutions of rainfall input

2018 ◽  
Author(s):  
Yingchun Huang ◽  
András Bárdossy ◽  
Ke Zhang
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
Daily Precipitation ◽  
Model Performance ◽  
Upstream Region ◽  
High Temporal Resolution ◽  
Dense Network ◽  
Streamflow Prediction ◽  
Daily Streamflow ◽  
Temporal And Spatial

Abstract. As the most important input for rainfall-runoff models, precipitation is usually observed at specific sites on a daily or sub-daily time scale and requires interpolation for further application. This study aims to explore that for a given objective function, whether a higher temporal and spatial resolution of precipitation could provide an improvement in model performance. Four different gridded hourly and daily precipitation datasets, with a spatial resolution of 1 km * 1 km for the Baden-Wurttemberg state of Germany, were constructed using a combination of data from a dense network of daily rainfall stations and a less dense network of pluviometers with high temporal-resolution rainfall observations. Two different flavors of HBV models with different model structures, lumped and spatially distributed, were used to test the sensitivity of model performance on the spatial resolution of precipitation. For four selected mesoscale catchments located at the upstream region of Baden-Wurttemberg, these four precipitation datasets were used to simulate the daily discharges using both lumped and semi-distributed HBV models. Different possibilities of improving the accuracy of daily streamflow prediction were investigated. Three main results were obtained from this study: (1) a higher temporal resolution of precipitation improved the model performance if the observation density was high; (2) a combination of observed high temporal-resolution observations with disaggregated daily precipitation leads to a further improvement in the model performance; (3) for the present research, the increase of spatial resolution improved the performance of the model insubstantially or only marginally for most of the study catchments.

scholarly journals An automatic contrail tracking algorithm

2010 ◽  
Vol 3 (4) ◽  
pp. 1089-1101 ◽  
Author(s):  
M. Vazquez-Navarro ◽  
H. Mannstein ◽  
B. Mayer
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
High Spatial Resolution ◽  
High Temporal Resolution ◽  
Cirrus Cloud ◽  
Linear Stage ◽  
Geostationary Satellites ◽  
Rapid Scan ◽  
Temporal And Spatial ◽  
Resolution Data

Abstract. A method designed to track the life cycle of contrail-cirrus using satellite data with high temporal and spatial resolution, from its formation to the final dissolution of the aviation-induced cirrus cloud is presented. The method follows the evolution of contrails from their linear stage until they are undistinguishable from natural cirrus clouds. Therefore, the study of the effect of aircraft-induced clouds in the atmosphere is no longer restricted to linear contrails and can include contrail-cirrus. The method takes advantage of the high spatial resolution of polar orbiting satellites and the high temporal resolution of geostationary satellites to identify the pixels that belong to an aviation induced cloud. The high spatial resolution data of the MODIS sensor is used for contrail detection, and the high temporal resolution of the SEVIRI sensor in the Rapid Scan mode is used for contrail tracking. An example is included in which the method is applied to the study of a long lived contrail over the bay of Biscay.

scholarly journals An automatic contrail tracking algorithm

2010 ◽  
Vol 3 (2) ◽  
pp. 1439-1494
Author(s):  
M. Vazquez-Navarro ◽  
H. Mannstein ◽  
B. Mayer
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
High Spatial Resolution ◽  
High Temporal Resolution ◽  
Cirrus Cloud ◽  
Linear Stage ◽  
Geostationary Satellites ◽  
Rapid Scan ◽  
Temporal And Spatial ◽  
Resolution Data

Abstract. A method designed to track the life cycle of contrail-cirrus using satellite data with high temporal and spatial resolution, from its formation to the final dissolution of the aviation-induced cirrus cloud is presented. The method follows the evolution of contrails from their linear stage until they are undistinguishable from natural cirrus clouds. Therefore, the study of the effect of aircraft-induced clouds in the atmosphere is no longer restricted to linear contrails and can include contrail-cirrus. The method takes advantage of the high spatial resolution of polar orbiting satellites and the high temporal resolution of geostationary satellites to identify the pixels that belong to an aviation induced cloud. The high spatial resolution data of the MODIS sensor is used for contrail detection, and the high temporal resolution of the SEVIRI sensor in the Rapid Scan mode is used for contrail tracking. An example is included in which the method is applied to the study of a long lived contrail over the bay of Biscay.

scholarly journals On quality of radar rainfall with respect to temporal and spatial resolution for application to urban areas

2016 ◽  
Vol 24 (1) ◽  
pp. 19-30 ◽  
Author(s):  
Jungsoo Yoon ◽  
Jingul Joo ◽  
Chulsang Yoo ◽  
Seokhwan Hwang ◽  
Sanghun Lim
Keyword(s):  
Spatial Resolution ◽  
Urban Areas ◽  
Radar Rainfall ◽  
Temporal And Spatial

Transient Spatial Attention Degrades Temporal Resolution

2003 ◽  
Vol 14 (3) ◽  
pp. 225-231 ◽  
Author(s):  
Yaffa Yeshurun ◽  
Liat Levy
Keyword(s):  
Visual Perception ◽  
Spatial Attention ◽  
Spatial Resolution ◽  
Temporal Resolution ◽  
Direct Manipulation ◽  
Single Flash ◽  
Temporal And Spatial ◽  
First Time ◽  
Attentional Mechanisms

To better understand the interplay between the temporal and spatial components of visual perception, we studied the effects of transient spatial attention on temporal resolution. Given that spatial attention sharpens spatial resolution, can it also affect temporal resolution? To assess temporal resolution, we measured the two-flash fusion threshold. When two flashes of light are presented successively to the same location, the two-flash fusion threshold is the minimal interval between the flashes at which they are still perceived as two flashes, rather than a single flash. This assessment of temporal resolution was combined with peripheral precuing—a direct manipulation of transient spatial attention. This allowed us to demonstrate, for the first time, that spatial attention can indeed affect temporal resolution. However, in contrast to its effect on spatial resolution, spatial attention degrades temporal resolution. Two attentional mechanisms that could account for both attentional effects—enhanced spatial resolution and reduced temporal resolution—are discussed.

scholarly journals Defining the optimal temporal and spatial resolution for cardiovascular magnetic resonance imaging feature tracking

2021 ◽  
Vol 23 (1) ◽  
Author(s):  
Sören J. Backhaus ◽  
Georg Metschies ◽  
Marcus Billing ◽  
Jonas Schmidt-Rimpler ◽  
Johannes T. Kowallick ◽  
...  
Keyword(s):  
Cardiovascular Magnetic Resonance ◽  
Magnetic Resonance ◽  
Spatial Resolution ◽  
Temporal Resolution ◽  
Feature Tracking ◽  
Cardiac Cycle ◽  
Left Ventricular ◽  
Incremental Value ◽  
Temporal And Spatial ◽  
Lower Temporal Resolution

Abstract Background Myocardial deformation analyses using cardiovascular magnetic resonance (CMR) feature tracking (CMR-FT) have incremental value in the assessment of cardiac function beyond volumetric analyses. Since guidelines do not recommend specific imaging parameters, we aimed to define optimal spatial and temporal resolutions for CMR cine images to enable reliable post-processing. Methods Intra- and inter-observer reproducibility was assessed in 12 healthy subjects and 9 heart failure (HF) patients. Cine images were acquired with different temporal (20, 30, 40 and 50 frames/cardiac cycle) and spatial resolutions (high in-plane 1.5 × 1.5 mm through-plane 5 mm, standard 1.8 × 1.8 x 8mm and low 3.0 × 3.0 x 10mm). CMR-FT comprised left ventricular (LV) global and segmental longitudinal/circumferential strain (GLS/GCS) and associated systolic strain rates (SR), and right ventricular (RV) GLS. Results Temporal but not spatial resolution did impact absolute strain and SR. Maximum absolute changes between lowest and highest temporal resolution were as follows: 1.8% and 0.3%/s for LV GLS and SR, 2.5% and 0.6%/s for GCS and SR as well as 1.4% for RV GLS. Changes of strain values occurred comparing 20 and 30 frames/cardiac cycle including LV and RV GLS and GCS (p < 0.001–0.046). In contrast, SR values (LV GLS/GCS SR) changed significantly comparing all successive temporal resolutions (p < 0.001–0.013). LV strain and SR reproducibility was not affected by either temporal or spatial resolution, whilst RV strain variability decreased with augmentation of temporal resolution. Conclusion Temporal but not spatial resolution significantly affects strain and SR in CMR-FT deformation analyses. Strain analyses require lower temporal resolution and 30 frames/cardiac cycle offer consistent strain assessments, whilst SR measurements gain from further increases in temporal resolution.

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