نتایج جستجو برای: temporal variability

تعداد نتایج: 402760  

2001
H. J. Foster M. J. Lees H. S. Wheater C. Neal B. Reynolds

Recent concern about the risk to biota from acidification in upland areas, due to air pollution and land-use change (such as the planting of coniferous forests), has generated a need to model catchment hydro-chemistry to assess environmental risk and define protection strategies. Previous approaches have tended to concentrate on quantifying either spatial variability at a regional scale or temp...

2010
Feng Han Steven A. Cummer

[1] Significant temporal variability of the nighttime D region is well known, but its inaccessibility means that the time scales, magnitudes, and sources for that variability are not well understood. We probed the ionospheric D region by measuring the high‐power broadband very low frequency (VLF) signals launched by lightning and propagating in the Earth‐ionosphere waveguide. We analyzed broadb...

Ahmad Shalbaf, Jamie Sleigh, Sanaz Jafari,

Background: Ensuring adequate depth of anesthesia during surgery is essential for anesthesiologists to prevent the occurrence of unwanted alertness during surgery or failure to return to consciousness. Since the purpose of using anesthetics is to affect the central nervous system, brain signal processing such as electroencephalography (EEG) can be used to predict different levels of anesthesia....

2016
Simon Chamaillé-Jammes Anaïs Charbonnel Stéphane Dray Hillary Madzikanda Hervé Fritz

The spatial structuring of populations or communities is an important driver of their functioning and their influence on ecosystems. Identifying the (in)stability of the spatial structure of populations is a first step towards understanding the underlying causes of these structures. Here we studied the relative importance of spatial vs. interannual variability in explaining the patterns of abun...

Journal: :Ecology 2007
David A Vasseur Ursula Gaedke

Community biomass is often less variable than the biomasses of populations within the community, yet attempts to implicate compensatory dynamics between populations as a cause of this relationship often fail. In part, this may be due to the lack of appropriate metrics for variability, but there is also great potential for large-scale processes such as seasonality or longer-term environmental ch...

2012
E. D. P. Cousins S. G. Shepherd

[1] The statistical characteristics of small-scale spatial and temporal electric field variability in the high-latitude regions of Earth’s ionosphere are investigated using 48 months of data from the Super Dual Auroral Radar Network (SuperDARN) radars in both hemispheres. Electric field fluctuations on spatial scales between 45 km and 450 km and on temporal scales between 2 min and 20 min are c...

Journal: :Entropy 2017
Sufen Wang Vijay P. Singh

The relationship between soil water content (SWC) and vegetation, topography, and climatic conditions is critical for developing effective agricultural water management practices and improving agricultural water use efficiency in arid areas. The purpose of this study was to determine how crop cover influenced spatial and temporal variation of soil water. During a study, SWC was measured under m...

Journal: :Theoretical population biology 2012
Stephen P Ellner Sebastian J Schreiber

We analyze how temporal variability in local demography and dispersal combine to affect the rate of spread of an invading species. Our model combines state-structured local demography (specified by an integral or matrix projection model) with general dispersal distributions that may depend on the state of the individual or its parent. It allows very general patterns of stationary temporal varia...

Journal: :Journal of environmental quality 2010
R D Harmel R M Slade R L Haney

Science-based sampling methodologies are needed to enhance water quality characterization for setting appropriate water quality standards, developing Total Maximum Daily Loads, and managing nonpoint source pollution. Storm event sampling, which is vital for adequate assessment of water quality in small (wadeable) streams, is typically conducted by manual grab or integrated sampling or with an a...

2004
Corinna Schrum Irina Alekseeva

The 3-D coupled biophysical model ECOSMO (ECOSystem MOdel) has been applied to simulate the spatial and temporal variability of primary and secondary production and biomass in the North Sea in 1984. In order to assess the spatial and temporal dynamics of these components, statistical methods based on empirical orthogonal function analysis (EOF) are introduced to biological oceanography and ecos...

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