Self-Organizing Maps for the Classification of Spatial and Temporal Variability of Tornado-Favorable Parameters

2021 ◽  
Keyword(s):  
Temporal Variability ◽  
Temporal Distribution ◽  
Environmental Parameters ◽  
Environmental Parameter ◽  
Spatial And Temporal Variability ◽  
Self Organizing Maps ◽  
Geographical Regions ◽  
Baseline Evaluation ◽  
Time Specific ◽  
Self Organizing

Abstract A nuanced analysis of the spatial and temporal distribution of supercell tornadoes and the characteristics of the near-storm environments associated with those tornadoes is critical to improving our understanding of the range of environments that can be considered tornado-favorable. This work classifies both supercell tornado probabilities and their associated environmental parameters on hourly and daily time scales based on geographical regions: regional probability of tornado events and the probability of deviation above or below the median tornadic near-storm environmental parameter values are estimated by kernel density estimation and classified by self-organizing maps (SOMs). The SOM classification for tornado probability allows for further examination of the deviation of the environmental parameters from the median for each probability cluster. Regions that have similar tornado probabilities but differ in the deviation of the environmental parameters (“parameter anomalies”) are also highlighted using SOMs. The anomaly patterns for different regions and parameters generally evolve along either seasonal or diurnal scales, but rarely both, highlighting the need for flexible models of tornado potential based on the near-storm environment. The spatial and temporal variability of parameter anomalies add complexity to traditional forecasting approaches that depend upon a fixed set of environmental parameter thresholds. This work highlights the need to develop region-specific and potentially time-specific environmental baseline evaluation to improve forecast and warning skill.

Implementation of Self-Organizing Maps (SOM) to analyses of environmental parameters and phytoplankton biomass in a macrotidal estuary and artificial lake

2012 ◽  
Vol 93 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Roksana Jahan ◽  
Hyu Chang Choi ◽  
Young Seuk Park ◽  
Young Cheol Park ◽  
Ji Ho Seo ◽  
...  
Keyword(s):  
Phytoplankton Biomass ◽  
Algal Blooms ◽  
Suspended Solids ◽  
Inorganic Nitrogen ◽  
Environmental Parameters ◽  
Ecological Data ◽  
Self Organizing Maps ◽  
Macrotidal Estuary ◽  
Phytoplankton Communities ◽  
Self Organizing

Self-Organizing Maps (SOM) have been used for patterning and visualizing ten environmental parameters and phytoplankton biomass in a mactrotidal (>10 m) Gyeonggi Bay and artificial Shihwa Lake during 1986–2004. SOM segregated study areas into four groups and ten subgroups. Two strikingly alternative states are frequently observed: the first is a diverse non-eutrophic state designated by three groups (SOM 1–3), and the second is a eutrophic state (SOM 4: Shihwa Lake and Upper Gyeonggi Bay; summer season) characterized by enhanced nutrients (3 mg l−1 dissolved inorganic nitrogen, 0.1 mg l−1 PO4) that act as a signal and response to that signal as algal blooms (24 µg chlorophyll-a l−1). Bloom potential in response to nitrification is affiliated with high temperature (r = 0.26), low salinity (r = −0.40) and suspended solids (r = –0.27). Moreover, strong stratification in the Shihwa Lake has accelerated harmful algal blooms and hypoxia. The non-eutrophic states (SOM 1–3) are characterized by macro-tidal estuaries exhibiting a tolerance to pollution with nitrogen-containing nutrients and retarding any tendency toward stratification. SOM 1 (winter) is more distinct from SOM 4 due to higher suspended solids (>50 mg l−1) caused by resuspension that induces light limitation and low chlorophyll-a (<5 µg l−1). In addition, eutrophication-induced shifts in phytoplankton communities are noticed during all the seasons in Gyeonggi Bay. Overall, SOM showed high performance for visualization and abstraction of ecological data and could serve as an efficient ecological map that can specify blooming regions and provide a comprehensive view on the eutrophication process in a macrotidal estuary.

scholarly journals FUZZY LOGIC IN THE SPATIAL AND TEMPORAL DISTRIBUTION IN THE QUALITY OF THE BEVERAGE IN CONILON COFFEE

2019 ◽  
Vol 14 (2) ◽  
pp. 163
Author(s):  
Abel Souza Da Fonseca ◽  
Julião Soares De Souza Lima ◽  
Samuel De Assis Silva ◽  
Maria Christina Junger Delôgo Dardengo ◽  
Alexandre Candido Xavier
Keyword(s):  
Spatial Dependence ◽  
Temporal Variability ◽  
Temporal Distribution ◽  
Spherical Model ◽  
Coffea Canephora ◽  
Descriptive Statistics ◽  
Fuzzy Classification ◽  
Spatial And Temporal Variability ◽  
Mouth Feel

<p>The objective in this study was to evaluate the spatial and temporal variability of the beverage quality by applying the fuzzy classification in the final global sensory analysis, for Coffea canephora Pierre ex A. Froehner, in two consecutive harvests. The studied variables were: fragrance (aroma), flavor, bitterness (sweetness), set, balance, cleaning, aftertaste, mouth feel, uniformity, salinity (acidity) and drink (global note). To the average overall scores of the drinks obtained on the cup-tasting at 80.0 points of a sampling, the mesh has applied the function of association of the fuzzy classification linear model to determine the degree of pertinence. The data were analyzed by the descriptive statistics and then by geostatistics to verify the existence and quantify the degree of spatial dependence of the variables. In the interval classified as “very good coffee” is found in the global average grade, in the two harvests. The methodology fuzzy applied in the global beverage note of the coffee conilon seminal made it possible to determine their spatial variability in the same distribution pattern in the two harvests, close ranges, and adjustments to the spherical model, which was confirmed by the spatial correlation of 61.6% among the fuzzy maps for the global score</p>

Seasonal variability of phytoplankton in the shallow waters of the southern Baltic Sea

2018 ◽  
Vol 33 (1) ◽  
pp. 9-15
Author(s):  
Iwona Zabroś ◽  
Marlena Mioskowska
Keyword(s):  
Baltic Sea ◽  
Temporal Distribution ◽  
Environmental Parameters ◽  
Spatial And Temporal Variability ◽  
Sample Collection ◽  
The Baltic Sea ◽  
Mean Values ◽  
Southern Baltic Sea ◽  
Southern Baltic ◽  
The Baltic

The Baltic Sea is characterized by a seasonal variation of phytoplankton structure. These organisms are particularly sensitive to changes in various environmental parameters. Cyclic, recurring annually fluctuation of species composition, abundance and biomass of phytoplankton is a consequence of these changes. Spatial and temporal variability of particular groups of phytoplankton is not the same in different areas of the Baltic Sea. The purpose of this work was to determine the spatial and temporal distribution of phytoplankton in three chosen areas of the coastal zone of the southern Baltic Sea (Ustka, Poddąbie and Rowy) in the period of November 2014 - September 2016. Mean values of abundance and biomass of phytoplankton for the surveyed areas were typical for this type of coastal waters. In each of the surveyed areas the same dominat species in terms of the abundance and biomass were observed. A growth of diatoms was recorded only in the area of Ustka, which could have been caused by the inflow of river waters. Seasonal surveys of phytoplankton indicated that in the case of the studies regarding this parameter – taxonomic composition, abundance and biomass in the same surveyed area were similar at the three research stations (e.g. 75-80%), depending on the season of the year. On this basis, it was concluded that, whether carrying out the monitoring of phytoplankton or planned investments, the sample collection frequency had a greater significance than the number of research stations.

Clustering of Zika viruses originating from different geographical regions using computational sequence descriptors

2019 ◽  
Vol 16 ◽  
Author(s):  
Marjan Vračko ◽  
Subhash C. Basak ◽  
Dwaipayan Sen ◽  
Ashesh Nandy
Keyword(s):  
Zika Virus ◽  
Virus Genome ◽  
Host Cells ◽  
Genome Sequences ◽  
Region Of Origin ◽  
Self Organizing Maps ◽  
Data Set ◽  
Mahalanobis Distances ◽  
Geographical Regions ◽  
Self Organizing

: In this report we consider a data set, which consists of 310 Zika virus genome sequences taken from different continents, Africa, Asia and South America. The sequences, which were compiled from GenBank, were derived from the host cells of different mammalian species (Simiiformes, Aedes opok, Aedes africanus, Aedes luteocephalus, Aedes dalzieli, Aedes aegypti, and Homo sapiens). For chemometrical treatment the sequences have been represented by sequence descriptors derived from their graphs or neighborhood matrices. The set was analyzed with three chemometrical methods: Mahalanobis distances, principal component analysis (PCA) and self organizing maps (SOM). A good separation of samples with respect to the region of origin was observed using these three methods. Background: Study of 310 Zika virus genome sequences from different continents. Objective: To characterize and compare Zika virus sequences from around the world using alignment-free sequence comparison and chemometrical methods. Method: Mahalanobis distance analysis, self organizing maps, principal components were used to carry out the chemometrical analyses of the Zika sequence data. Results: Genome sequences are clustered with respect to the region of origin (continent, country) Conclusion: Africa samples are well separated from Asian and South American ones.

Temporal and spatial variability of the potentially toxic Pseudo-nitzschia spp. in a eutrophic estuary (Sea of Marmara)

2016 ◽  
Vol 97 (7) ◽  
pp. 1483-1494 ◽  
Author(s):  
Seyfettin Tas ◽  
Nina Lundholm
Keyword(s):  
Temporal Variability ◽  
Secchi Depth ◽  
Light Availability ◽  
Environmental Parameters ◽  
Significant Negative Correlation ◽  
Spatial And Temporal Variability ◽  
Golden Horn ◽  
Spatial Differences ◽  
Moderate Salinity ◽  
High Concentrations

Spatial and temporal variability and bloom formation of the potentially toxic diatom Pseudo-nitzschia spp. was investigated weekly to monthly from October 2009 to October 2010 in a eutrophic estuary, the Golden Horn. Pseudo-nitzschia spp. were detected in 195 of 512 samples (38%) collected throughout the year. Two species, P. calliantha and P. pungens, were identified based on the SEM examination. Blooms of Pseudo-nitzschia occurred in the lower and middle estuary in January and May. The bloom in January mainly comprised P. calliantha. In the bloom in early May, P. calliantha made up 72% of the Pseudo-nitzschia cells and P. pungens 28%. However, the contribution of P. pungens increased to 83% in late May. The Pseudo-nitzschia blooms occurred at low temperature (9–15°C) and moderate salinity (17–18), and for P. calliantha a significant negative correlation was found with temperature and a significant positive correlation with salinity. The percentage of Pseudo-nitzschia cells decreased gradually from lower to upper estuary (59–14%), correlating with a decrease in Secchi depth (5.5–0.5 m). Principal components analyses (PCA) were used to explore the spatial and temporal variability of environmental factors in relation to Pseudo-nitzschia abundances, and showed that NH4, pH, Secchi depth and DO values were the most important factors reflecting spatial differences, while temperature, salinity, Chl-a and Si:N were more important factors showing temporal differences. High abundances of P. pungens correlated mainly with pH, Secchi depth and DO values, whereas P. calliantha also correlated with NO3 + NO2. Low light availability due to high concentrations of suspended material and very variable environmental conditions (e.g. pH, DO and NH4) may have limited growth of Pseudo-nitzschia in the upper estuary. Regular monitoring of Pseudo-nitzschia is important for improving the understanding of the influence of environmental parameters on bloom dynamics in the study area.

scholarly journals Antarctic sea ice: a self-organizing map-based perspective

2007 ◽  
Vol 46 ◽  
pp. 391-396 ◽  
Author(s):  
David B. Reusch ◽  
Richard B. Alley
Keyword(s):  
Sea Ice ◽  
Rapid Identification ◽  
Rate Of Change ◽  
Spatial And Temporal Variability ◽  
Self Organizing Map ◽  
Sea Ice Extent ◽  
Self Organizing Maps ◽  
Antarctic Sea Ice ◽  
Sea Ice Edge ◽  
Self Organizing

AbstractSelf-organizing maps (SOMs) provide a powerful, non-linear technique to optimally summarize a complex geophysical dataset using a user-selected number of ‘icons’ or SOM states, allowing rapid identification of preferred patterns, predictability of transitions, rates of transitions, and hysteresis in cycles. The use of SOMs is demonstrated here through application to a 24 year dataset (1973–96) of monthly Antarctic sea-ice edge positions. Variability in sea-ice extent, concentration and other physical characteristics is an important component of the Earth’s dynamic climate system, particularly in the Southern Hemisphere where annual changes in sea-ice extent (temporarily) double the size of the Antarctic cryosphere. SOM-based patterns concisely capture the spatial and temporal variability in these data, including the annual progression of expansion and retreat, a general eastward propagation of anomalies during the winter, and sub-annual variability in the rate of change in extent at different times of the year (e.g. retreat in January is faster than in November). There is also often a general seasonal hysteresis, i.e. monthly anomalies during cooling follow a different spatial path than during warming.

scholarly journals Modeling characterization of the vertical and temporal variability of environmental DNA in the mesopelagic ocean

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Elizabeth Andruszkiewicz Allan ◽  
Michelle H. DiBenedetto ◽  
Andone C. Lavery ◽  
Annette F. Govindarajan ◽  
Weifeng G. Zhang
Keyword(s):  
Vertical Distribution ◽  
Water Column ◽  
Temporal Variability ◽  
Mechanistic Model ◽  
Temporal Distribution ◽  
Environmental Dna ◽  
Vertical Displacement ◽  
Physical Parameters ◽  
Spatial And Temporal Variability ◽  
The Impact

AbstractIncreasingly, researchers are using innovative methods to census marine life, including identification of environmental DNA (eDNA) left behind by organisms in the water column. However, little is understood about how eDNA is distributed in the ocean, given that organisms are mobile and that physical and biological processes can transport eDNA after release from a host. Particularly in the vast mesopelagic ocean where many species vertically migrate hundreds of meters diurnally, it is important to link the location at which eDNA was shed by a host organism to the location at which eDNA was collected in a water sample. Here, we present a one-dimensional mechanistic model to simulate the eDNA vertical distribution after its release and to compare the impact of key biological and physical parameters on the eDNA vertical and temporal distribution. The modeled vertical eDNA profiles allow us to quantify spatial and temporal variability in eDNA concentration and to identify the most important parameters to consider when interpreting eDNA signals. We find that the vertical displacement by advection, dispersion, and settling has limited influence on the eDNA distribution, and the depth at which eDNA is found is generally within tens of meters of the depth at which the eDNA was originally shed from the organism. Thus, using information about representative vertical migration patterns, eDNA concentration variability can be used to answer ecological questions about migrating organisms such as what depths species can be found in the daytime and nighttime and what percentage of individuals within a species diurnally migrate. These findings are critical both to advance the understanding of the vertical distribution of eDNA in the water column and to link eDNA detection to organism presence in the mesopelagic ocean as well as other aquatic environments.

Spatial and temporal variability of sea ambient noise as an anthropogenic pressure index: the case of the Cres-Lošinj archipelago, Croatia

2012 ◽  
Vol 93 (1) ◽  
pp. 27-36 ◽  
Author(s):  
Nikolina Rako ◽  
Marta Picciulin ◽  
Ivica Vilibić ◽  
Caterina M. Fortuna
Keyword(s):  
Temporal Variability ◽  
Ambient Noise ◽  
Sound Pressure ◽  
Bottlenose Dolphins ◽  
Temporal Distribution ◽  
Spatial And Temporal Variability ◽  
Anthropogenic Pressure ◽  
Marine Habitat ◽  
Low Frequencies ◽  
North Eastern

This study monitors the spatial and temporal variability of sea ambient noise (SAN) in the Cres-Lošinj archipelago from 2007 to 2009 (north-eastern Adriatic Sea, Croatia). The archipelago is an important marine habitat for many protected species, including the bottlenose dolphin (Tursiops truncatus) that is considered as vulnerable to disturbance from intense local vessel traffic. Systematic monthly sampling of SAN was carried out at ten predefined acoustic stations. Data on the presence, type and distance of vessels from these stations was also collected during sampling and vessels were allocated into four main classes. A sample of noise produced by a representative vessel of each vessel class was collected and the noise levels were extracted on the 1/3 octave band standard centre frequencies. All the recordings were analysed in terms of instantaneous sound pressure level (LLSP, L-weighted, 63 Hz–20 kHz, root mean square fast). The equivalent continuous sound pressure levels (LLeq) for vessel and SAN were calculated averaging the LLSP of vessel and SAN samples. Results indicate an increase of SAN levels particularly in the range of low frequencies (63 Hz–1 kHz) during the tourist season. A positive relationship was found between the spatial and temporal distribution of SAN and seasonal changes in anthropogenic pressure, in terms of vessel traffic. Potential implications for local marine life, with particular reference to bottlenose dolphins, are discussed.

scholarly journals Spatial and temporal variability of nitrogen load from catchment and retention along a river network: a case study in the upper Xin'anjiang catchment of China

2015 ◽  
Vol 47 (4) ◽  
pp. 869-887 ◽  
Author(s):  
Ai Wang ◽  
Lihua Tang ◽  
Dawen Yang
Keyword(s):  
Temporal Variability ◽  
Temporal Distribution ◽  
River Network ◽  
Spatial And Temporal Variability ◽  
Point Source Pollution ◽  
Cropland Area ◽  
Scenarios Analysis ◽  
Retention Characteristics ◽  
Water Resources Protection

Understanding the spatial and temporal variability of nitrogen load and characteristics of retention along a river network is important for land management and water resources protection. This study employs a geomorphology-based non-point source pollution model (GBNP) to simulate the hillslope hydrological processes and transport of sediment and pollutants in the upper Xin'anjiang (XAJ) catchment. Based on the simulation, the spatial and temporal distribution of total nitrogen (TN) load from hillslopes and retention characteristics along the river network are analyzed. The results indicate that annual TN load ranges from 0.54 ton/km2 to 1.88 ton/km2 and is relatively higher during spring and summer. Average TN load positively correlates with irrigated cropland area (r =0.820) and negatively correlates with forest (r = −0.43). Seasonal TN retention ratios in the river network range from 0% to 81%, and streams of order 1 in the Horton–Strahler system have the highest retention ratio and are followed by orders 2, 3, and 4, which are mainly determined by the river hydraulic properties. Results of scenarios analysis demonstrate that TN retention ratios in the river network increase with TN load from hillslopes, but reach a maximum value rapidly, which indicates the limitation of the self-purification capacity of rivers.

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