scholarly journals Reconstruction of satellite time series with a dynamic smoother

2021 ◽  
Author(s):  
Jordan Graesser ◽  
Radost Stanimirova ◽  
Mark Friedl
Keyword(s):  
Time Series ◽  
Land Cover ◽  
High Performance ◽  
Data Availability ◽  
South American ◽  
Reconstruction Methods ◽  
Temporal Smoothing ◽  
Noisy Signals ◽  
Short And Long Term

Time series reconstruction methods---used to generate gap-free time series of satellite observations---were historically designed for sensors with frequent image acquisitions. Since 2008, interest in leveraging time series methods has shifted from sensors such as AVHRR and MODIS to Landsat because of free, higher-resolution data availability and improved access to high-performance compute systems. Existing methods are typically designed for specific applications such as land cover classification or for estimating the timing of phenology events.Moreover, approaches developed for specific ecological systems, such as tropical forests or temperate agriculture, often do not generalize well across land cover, vegetation, and climate types. In this study, we introduce a dynamic temporal smoothing (DTS) method to reconstruct sparse, noisy signals into dense time series at regular intervals. The DTS is a weighted smoother with dynamic parameters that is applied over a signal. The smoother is intended to have wide applicability, with particular focus on applications in vegetation remote sensing. In this paper we present and illustrate the DTS over short- and long-term Landsat (TM, ETM+, and OLI) time series and demonstrate the effectiveness of robust gap-filling over a range of landscapes in the South American Southern Cone region.

scholarly journals Long-term effects of climate and land cover change on freshwater provision in the tropical Andes

2015 ◽  
Vol 12 (6) ◽  
pp. 5219-5250 ◽  
Author(s):  
A. Molina ◽  
V. Vanacker ◽  
E. Brisson ◽  
D. Mora ◽  
V. Balthazar
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Land Cover ◽  
Land Cover Change ◽  
Catchment Area ◽  
Strong Increase ◽  
Tropical Andes ◽  
Evaporative Water ◽  
Exotic Tree

Abstract. Andean headwater catchments play a pivotal role to supply fresh water for downstream water users. However, few long-term studies exist on the relative importance of climate change and direct anthropogenic perturbations on flow regimes. In this paper, we assess multi-decadal change in freshwater provision based on long time series (1974–2008) of hydrometeorological data and land cover reconstructions for a 282 km2 catchment located in the tropical Andes. Three main land cover change trajectories can be distinguished: (1) rapid decline of native vegetation in montane forest and páramo ecosystems in ~1/5 or 20% of the catchment area, (2) expansion of agricultural land by 14% of the catchment area, (3) afforestation of 12% of native páramo grasslands with exotic tree species in recent years. Given the strong temporal variability of precipitation and streamflow data related to El Niño–Southern Oscillation, we use empirical mode decomposition techniques to detrend the time series. The long-term increasing trend in rainfall is remarkably different from the observed changes in streamflow that exhibit a decreasing trend. Hence, observed changes in streamflow are not the result of long-term climate change but very likely result from direct anthropogenic disturbances after land cover change. Partial water budgets for montane cloud forest and páramo ecosystems suggest that the strongest changes in evaporative water losses are observed in páramo ecosystems, where progressive colonization and afforestation of high alpine grasslands leads to a strong increase in transpiration losses.

Auscultation d'une culée du pont de Portneuf à l'aide d'une inclusion de béton instrumentée (CIUS)

1996 ◽  
Vol 23 (5) ◽  
pp. 1129-1136
Author(s):  
Axel-Pierre Bois ◽  
Mohamed Lachemi ◽  
Gérard Ballivy
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Coefficient Of Thermal Expansion ◽  
Concrete Bridge ◽  
Thermal Gradients ◽  
Bridge Monitoring ◽  
Shrinkage And Creep ◽  
First Results ◽  
Short And Long Term

The Portneuf Bridge, built in 1992, is the first air-entrained high-performance concrete bridge in North America. To understand its short and long term behaviour, an auscultation program has been set. Hence, a cylindrical concrete inclusion of the Université de Sherbrooke was installed in one of the abutments of the bridge. The aim of this study is to present the first results thus acquired. The analysis of the results allowed to calculate the coefficient of thermal expansion of the concrete and to assess deformation variations due to shrinkage and creep and the effects of rebar–concrete interaction in the upper abutment region. Moreover, the presence of thermal gradients, which creates nonisotropic deformations, has been established. Key words: high-performance concrete, deformations, thermal gradients, instrumentation, bridge, monitoring. [Journal translation]

Habitat mapping and change assessment of coastal wetlands by using Sentinel-2 time series and ecological expert knowledge

2020 ◽  
Author(s):  
Maria Adamo ◽  
Valeria Tomaselli ◽  
Francesca Mantino ◽  
Cristina Tarantino ◽  
Palma Blonda
Keyword(s):  
Time Series ◽  
Land Cover ◽  
Coastal Wetlands ◽  
Expert Knowledge ◽  
Land Reclamation ◽  
Habitat Mapping ◽  
The Mediterranean ◽  
The Impact ◽  
Sentinel 2

<p>Coastal wetlands are one of the most threatened ecosystems worldwide. In the Mediterranean Region, wetlands are undergoing rapid changes due to the increasing of human pressures (e.g. land reclamation, water resources exploitation) and climate changes (e.g. coastal erosion), with a resulting habitat degradation, fragmentation, and biodiversity loss.</p><p>Long-term habitat mapping and change detection are essential for the management of coastal wetlands as well as for evaluating the impact of conservation policies.</p><p>Earth observation (EO) data and techniques are a valuable resource for long-term habitat mapping, thanks to the large amount of available data and their high spatial and temporal resolution. In this study, we propose an approach based on the integration of time series of Sentinel-2 images and ecological expert knowledge for land cover (LC) mapping and automatic translation to habitats in coastal wetlands. In particular, the research relies on the exploitation of ecological rules based on combined information related to plant phenology, water seasonality of aquatic species, pattern zonation, and habitat geometric properties.</p><p>The methodology is applied to two Natura2000 sites, “Zone umide della Capitanata” and “Paludi presso il Golfo di Manfredonia”, located in the northeastern part of the Puglia region. These two areas are the most extensive wetlands of the Italian peninsula and the largest components of the Mediterranean wetland system.</p><p>Land Cover classes are labelled according to the FAO-LCCS taxonomy, which offers a framework to integrate EO data with in situ and ancillary data. Output habitat classes are labelled according to EUNIS habitat classification.</p>

scholarly journals Short and Long-Term Properties of High-Performance Concrete Containing Silica Fume for Bridge Deck Overlay

2005 ◽  
Vol 17 (5) ◽  
pp. 743-750
Author(s):  
Jong-Pil Won ◽  
Jung-Min Seo ◽  
Chang-Soo Lee ◽  
Hae-Kyun Park ◽  
Myeong-Sub Lee
Keyword(s):  
Silica Fume ◽  
High Performance ◽  
Bridge Deck ◽  
High Performance Concrete ◽  
Short And Long Term ◽  
Bridge Deck Overlay

scholarly journals Characterizing scaling laws in gut microbial dynamics from time series data: caution is warranted

2021 ◽  
Author(s):  
Xu-Wen Wang ◽  
Yang-Yu Liu
Keyword(s):  
Time Series ◽  
Gut Microbiota ◽  
Scaling Laws ◽  
Time Series Data ◽  
Series Data ◽  
Temporal Variance ◽  
Short And Long Term ◽  
Human And Mouse ◽  
Mouse Gut Microbiota

AbstractMany studies have revealed that both host and environmental factors can impact the gut microbial compositions, implying that the gut microbiota is considerably dynamic1–5. In their Article, Ji et al.6 performed comprehensive analysis of multiple high-resolution time series data of human and mouse gut microbiota. They found that both human and mouse gut microbiota dynamics can be characterized by several robust scaling laws describing short- and long-term changes in gut microbiota abundances, distributions of species residence and return times, and the correlation between the mean and the temporal variance of species abundances. They claimed that those scaling laws characterize both short- and long-term dynamics of gut microbiota. However, we are concerned that their interpretation is quite misleading, because all the scaling laws can be reproduced by the shuffled time series with completely randomized time stamps of the microbiome samples.

scholarly journals Air pollution, SARS-CoV-2 transmission, and COVID-19 outcomes: A state-of-the-science review of a rapidly evolving research area

2020 ◽  
Author(s):  
Anushka Bhaskar ◽  
Jay Chandra ◽  
Danielle Braun ◽  
Jacqueline Cellini ◽  
Francesca Dominici
Keyword(s):  
Air Pollution ◽  
Time Series ◽  
Health Outcomes ◽  
Study Design ◽  
Air Pollutant ◽  
Short Term ◽  
Cross Sectional ◽  
Short And Long Term ◽  
Long Term Studies

Background: As the coronavirus pandemic rages on, 692,000 (August 7, 2020) human lives and counting have been lost worldwide to COVID-19. Understanding the relationship between short- and long-term exposure to air pollution and adverse COVID-19 health outcomes is crucial for developing solutions to this global crisis. Objectives: To conduct a scoping review of epidemiologic research on the link between short- and long-term exposure to air pollution and COVID-19 health outcomes. Method: We searched PubMed, Web of Science, Embase, Cochrane, MedRxiv, and BioRxiv for preliminary epidemiological studies of the association between air pollution and COVID-19 health outcomes. 28 papers were finally selected after applying our inclusion/exclusion criteria; we categorized these studies as long-term studies, short-term time-series studies, or short-term cross-sectional studies. One study included both short-term time-series and a cross-sectional study design. Results: 27 studies of the 28 reported evidence of statistically significant positive associations between air pollutant exposure and adverse COVID-19 health outcomes; 11 of 12 long-term studies and all 16 short-term studies reported statistically significant positive associations. The 28 identified studies included various confounders, spatial and temporal resolutions of pollution concentrations, and COVID-19 health outcomes. Discussion: We discuss methodological challenges and highlight additional research areas based on our findings. Challenges include data quality issues, ecological study design limitations, improved adjustment for confounders, exposure errors related to spatial resolution, geographic variability in testing, mitigation measures and pandemic stage, clustering of health outcomes, and a lack of publicly available data and code.

Nonlinear Hierarchical MPC for Maximizing Aircraft Thermal Endurance

2020 ◽  
Author(s):  
Daniel D. Leister ◽  
Justin P. Koeln
Keyword(s):  
High Performance ◽  
Linear Models ◽  
Critical Role ◽  
Effective Control ◽  
Thermal Management System ◽  
Short And Long Term ◽  
Upper Level ◽  
Control Of Linear Systems ◽  
High Computational Efficiency

Abstract In modern high-performance aircraft, the Fuel Thermal Management System (FTMS) plays a critical role in the overall thermal energy management of the aircraft. Actuator and state constraints in the FTMS limit the thermal endurance and capabilities of the aircraft. Thus, an effective control strategy must plan and execute optimized transient fuel mass and temperature trajectories subject to these constraints over the entire course of operation. For the control of linear systems, hierarchical Model Predictive Control (MPC) has shown to be an effective approach to coordinating both short- and long-term system operation with reduced computational complexity. However, for controlling nonlinear systems, common approaches to system linearization may no longer be effective due to the long prediction horizons of upper-level controllers. This paper explores the limitations of using linear models for hierarchical MPC of the nonlinear FTMS found in aircraft. Numerical simulation results show that linearized models work well for lower-level controllers with short prediction horizons but lead to significant reductions in aircraft thermal endurance when used for upper-level controllers with long prediction horizons. Therefore, a mixed-linearity hierarchical MPC formulation is presented with a nonlinear upper-level controller and a linear lower-level controller to achieve both high performance and high computational efficiency.

scholarly journals Combined Use of Optical and Synthetic Aperture Radar Data for REDD+ Applications in Malawi

Land ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 116 ◽  
Author(s):  
Manuela Hirschmugl ◽  
Carina Sobe ◽  
Janik Deutscher ◽  
Mathias Schardt
Keyword(s):  
Time Series ◽  
Land Cover ◽  
Synthetic Aperture Radar ◽  
Data Availability ◽  
Synthetic Aperture ◽  
Optical Data ◽  
Series Data ◽  
Forest Mapping ◽  
Sar Data ◽  
Aperture Radar

Recent developments in satellite data availability allow tropical forest monitoring to expand in two ways: (1) dense time series foster the development of new methods for mapping and monitoring dry tropical forests and (2) the combination of optical data and synthetic aperture radar (SAR) data reduces the problems resulting from frequent cloud cover and yields additional information. This paper covers both issues by analyzing the possibilities of using optical (Sentinel-2) and SAR (Sentinel-1) time series data for forest and land cover mapping for REDD+ (Reducing Emissions from Deforestation and Forest Degradation) applications in Malawi. The challenge is to combine these different data sources in order to make optimal use of their complementary information content. We compare the results of using different input data sets as well as of two methods for data combination. Results show that time-series of optical data lead to better results than mono-temporal optical data (+8% overall accuracy for forest mapping). Combination of optical and SAR data leads to further improvements: +5% in overall accuracy for land cover and +1.5% for forest mapping. With respect to the tested combination methods, the data-based combination performs slightly better (+1% overall accuracy) than the result-based Bayesian combination.

scholarly journals Multidecadal change in streamflow associated with anthropogenic disturbances in the tropical Andes

2015 ◽  
Vol 19 (10) ◽  
pp. 4201-4213 ◽  
Author(s):  
A. Molina ◽  
V. Vanacker ◽  
E. Brisson ◽  
D. Mora ◽  
V. Balthazar
Keyword(s):  
Time Series ◽  
Land Cover ◽  
Land Cover Change ◽  
Agricultural Land ◽  
Southern Oscillation ◽  
Anthropogenic Disturbances ◽  
Tropical Andes ◽  
Water Users ◽  
Native Forests

Abstract. Andean headwater catchments are an important source of freshwater for downstream water users. However, few long-term studies exist on the relative importance of climate change and direct anthropogenic perturbations on flow regimes in these catchments. In this paper, we assess change in streamflow based on long time series of hydrometeorological data (1974–2008) and land cover reconstructions (1963–2009) in the Pangor catchment (282 km2) located in the tropical Andes. Three main land cover change trajectories can be distinguished during the period 1963–2009: (1) expansion of agricultural land by an area equal to 14 % of the catchment area (or 39 km2) in 46 years' time, (2) deforestation of native forests by 11 % (or −31 km2) corresponding to a mean rate of 67 ha yr−1, and (3) afforestation with exotic species in recent years by about 5 % (or 15 km2). Over the time period 1963–2009, about 50 % of the 64 km2 of native forests was cleared and converted to agricultural land. Given the strong temporal variability of precipitation and streamflow data related to El Niño–Southern Oscillation, we use empirical mode decomposition techniques to detrend the time series. The long-term increasing trend in rainfall is remarkably different from the observed changes in streamflow, which exhibit a decreasing trend. Hence, observed changes in streamflow are not the result of long-term change in precipitation but very likely result from anthropogenic disturbances associated with land cover change.

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