Wetlands Associated to the Basaltic Plateaus: Spatial Heterogeneity and Internal Variability of Wetlands. Case Study: Mallín Tropezón

2018 ◽  
pp. 231-270
Author(s):  
Elizabeth Mazzoni ◽  
Jorge Rabassa
Keyword(s):  
Spatial Heterogeneity ◽  
Internal Variability

scholarly journals Impacts of Spatial Heterogeneity and Temporal Non-Stationarity on Intensity-Duration-Frequency Estimates—A Case Study in a Mountainous California-Nevada Watershed

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1296 ◽  
Author(s):  
Huiying Ren ◽  
Z. Jason Hou ◽  
Mark Wigmosta ◽  
Ying Liu ◽  
L. Ruby Leung
Keyword(s):  
High Resolution ◽  
Spatial Heterogeneity ◽  
Time Windows ◽  
Exceedance Probability ◽  
Extreme Precipitation Events ◽  
Climate Simulations ◽  
Engineering Standards ◽  
Intensity Duration Frequency ◽  
Using Data

Changes in extreme precipitation events may require revisions of civil engineering standards to prevent water infrastructures from performing below the designated guidelines. Climate change may invalidate the intensity-duration-frequency (IDF) computation that is based on the assumption of data stationarity. Efforts in evaluating non-stationarity in the annual maxima series are inadequate, mostly due to the lack of long data records and convenient methods for detecting trends in the higher moments. In this study, using downscaled high resolution climate simulations of the historical and future periods under different carbon emission scenarios, we tested two solutions to obtain reliable IDFs under non-stationarity: (1) identify quasi-stationary time windows from the time series of interest to compute the IDF curves using data for the corresponding time windows; (2) introduce a parameter representing the trend in the means of the extreme value distributions. Focusing on a mountainous site, the Walker Watershed, the spatial heterogeneity and variability of IDFs or extremes are evaluated, particularly in terms of the terrain and elevation impacts. We compared observations-based IDFs that use the stationarity assumption with the two approaches that consider non-stationarity. The IDFs directly estimated based on the traditional stationarity assumption may underestimate the 100-year 24-h events by 10% to 60% towards the end of the century at most grids, resulting in significant under-designing of the engineering infrastructure at the study site. Strong spatial heterogeneity and variability in the IDF estimates suggest a preference for using high resolution simulation data for the reliable estimation of exceedance probability over data from sparsely distributed weather stations. Discrepancies among the three IDFs analyses due to non-stationarity are comparable to the spatial variability of the IDFs, underscoring a need to use an ensemble of non-stationary approaches to achieve unbiased and comprehensive IDF estimates.

scholarly journals Reducing bias in risk indices for COVID-19

2022 ◽  
Vol 17 (s1) ◽  
Author(s):  
Michał Paweł Michalak ◽  
Jack Cordes ◽  
Agnieszka Kulawik ◽  
Sławomir Sitek ◽  
Sławomir Pytel ◽  
...  
Keyword(s):  
Infectious Diseases ◽  
Spatial Heterogeneity ◽  
Disease Burden ◽  
Risk Indices ◽  
Study Evaluation ◽  
Dynamical Properties ◽  
Time Periods ◽  
Regional Disease ◽  
Over Time

Spatiotemporal modelling of infectious diseases such as coronavirus disease 2019 (COVID-19) involves using a variety of epidemiological metrics such as regional proportion of cases and/or regional positivity rates. Although observing changes of these indices over time is critical to estimate the regional disease burden, the dynamical properties of these measures, as well as crossrelationships, are usually not systematically given or explained. Here we provide a spatiotemporal framework composed of six commonly used and newly constructed epidemiological metrics and conduct a case study evaluation. We introduce a refined risk estimate that is biased neither by variation in population size nor by the spatial heterogeneity of testing. In particular, the proposed methodology would be useful for unbiased identification of time periods with elevated COVID-19 risk without sensitivity to spatial heterogeneity of neither population nor testing coverage.We offer a case study in Poland that shows improvement over the bias of currently used methods. Our results also provide insights regarding regional prioritisation of testing and the consequences of potential synchronisation of epidemics between regions. The approach should apply to other infectious diseases and other geographical areas.

scholarly journals Understanding the Internal Variability of Mudstones: Dark Mudstone of the Campano- Maastrichtian Mamu Formation as Case Study

2020 ◽  
Vol 24 (5) ◽  
pp. 845-851
Author(s):  
A.J. Edegbai ◽  
W.O. Emofurieta
Keyword(s):  
Particle Size ◽  
Sea Level ◽  
Research Work ◽  
Internal Variability ◽  
Gas Shale ◽  
Relative Sea Level ◽  
Quartz Content ◽  
Geomechanical Properties ◽  
Bottom To Top

The objective of this research work was to investigate approximately 6m of Campano-Maastrichtian dark mudstone outcropping at Uzebba, Benin Flank, SW Anambra Basin using sedimentological, geochemical, mineralogical, and palynofacies techniques. Our findings show that the mudstone succession can be subdivided into 3-broad units from bottom to top. Unit 1 is characterized by weak to moderate bioturbation, high quartz content (≥50 %) as well as grained dominated microfabric with planar to wavy laminations. Unit 2 has the lowest particle size, zero to mild bioturbation, low quartz content as well as matrix dominated microfabric with thin to indistinct laminations, which are mostly planar. Unit 3 show intermediate particle size, weak to moderate bioturbation, moderate quartz content as well as grain dominated microfabric with much thicker laminations than units 1and 2 that vary from wavy to curved. Geochemical and palynofacies proxies for detrital influx and paleoproductivity are congruent. They show that units 1 and 3 received significant detrital contribution as well as high terrestrial paleoproductivity under low relative sea level, which promoted the development of good petrophysical and geomechanical properties suitable for gas shale development. Conversely, Unit 2 received less  significant detrital contribution as well as increased marine paleoproductivity under higher relative sea level. Keywords: Detrital influx, paleoproductivity, unconventional reservoirs, Benin flank

Spatial heterogeneity of biodiversity value based on dominant species: Changbaishan Ecological Function Zone as a case study

2018 ◽  
Vol 38 (13) ◽  
Author(s):  
蔺琛 LIN Chen ◽  
龚明昊 GONG Minghao ◽  
刘洋 LIU Yang ◽  
潘旭 PAN Xu ◽  
朴正吉 PIAO Zhengji
Keyword(s):  
Spatial Heterogeneity ◽  
Dominant Species ◽  
Ecological Function

Resilience indicator for ecosystems subject to high risk of irreversible degradation: a probabilistic method based on Bayesian inference

2020 ◽  
Author(s):  
Yong Liu ◽  
Sifeng Wu
Keyword(s):  
Bayesian Inference ◽  
Spatial Heterogeneity ◽  
Lake Level ◽  
Probabilistic Method ◽  
Quantitative Measure ◽  
Lake Eutrophication ◽  
Ecosystem Degradation ◽  
Parameter Estimations ◽  
Wide Range

<p>Ecosystem degradation is usually abrupt and unexpected shifts in ecosystem states that cannot be easily reversed. Some ecosystems might be subject to high risks of irreversible degradation (<em>RID</em>) because of strong undesirable resilience. In this study, we propose a probabilistic method to quantify <em>RID</em> by measuring the probability of the recovering threshold being unattainable under real world scenarios. Bayesian inference was used for parameter estimations and the posteriors were used to calculate the threshold for recovery and thereby the probability of it being unattainable, i.e., <em>RID</em>. We applied this method to lake eutrophication as an example. Our case study supported our hypothesis that ecosystems could be subject to high <em>RID</em>, as shown by the lake having a <em>RID</em> of 72% at the whole lake level. Spatial heterogeneity of <em>RID</em> was significant and certain regions were more susceptible to irreversible degradation, whereas others had higher chances of recovery. This spatial heterogeneity provides opportunities for mitigation because targeting regions with lower <em>RID</em> is more effective. We also found that pulse disturbances and ecosystem-based solutions had positive influences on lowering the <em>RID</em>. Pulse disturbances had the most significant influence on regions with higher <em>RID</em>, while ecosystem-based solutions performed best for regions with moderate <em>RID</em>, reducing <em>RID</em> to almost 0. Our method provides a practical framework to identify sensitive regions for conservation as well as opportunities for mitigation, which is applicable to a wide range of ecosystems. Our findings highlighted the worst scenario of irreversible degradation by providing a quantitative measure of the risk, thus raising further requirements and challenges for sustainability.</p>

Quantifying internal variability in a regional climate model: a case study for Southern Africa

2011 ◽  
Vol 37 (7-8) ◽  
pp. 1335-1356 ◽  
Author(s):  
Julien Crétat ◽  
Clémence Macron ◽  
Benjamin Pohl ◽  
Yves Richard
Keyword(s):  
Regional Climate Model ◽  
Southern Africa ◽  
Climate Model ◽  
Regional Climate ◽  
Internal Variability

scholarly journals Inference of spatial heterogeneity in surface fluxes from eddy covariance data: A case study from a subarctic mire ecosystem

2020 ◽  
Vol 280 ◽  
pp. 107783 ◽  
Author(s):  
Peter Levy ◽  
Julia Drewer ◽  
Mathilde Jammet ◽  
Sarah Leeson ◽  
Thomas Friborg ◽  
...  
Keyword(s):  
Spatial Heterogeneity ◽  
Eddy Covariance ◽  
Surface Fluxes ◽  
Mire Ecosystem
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