Spatial Distribution Of Stations Research Articles

Seagrass spatial distribution based on density in the waters of Tunda Island, Banten

One of the coastal ecosystems on Tunda island is the seagrass ecosystem, which functions as a primary producer, breakwater, spawning ground, nursery ground, and feeding ground for fish. Mining of sea sand around this island can potentially result in environmental degradation. The purpose of this study was to determine the type, density and percentage of seagrass cover as well as the influence of environmental factors on seagrass species and their spatial distribution. The research was conducted in July 2019 at 14 stations around the island. The results showed that the species composition of seagrass from the stations on Tunda Island consisted of 6 species with a similarity index of more than 75% except at stations 6, 7, 10 and 13. Correspondence analysis shows that the spatial distribution of stations is different and is influenced by habitat characteristics. Thalassia hemprichii dominates the entire station, followed by Enhalus acoroides 6 stations, Halophila ovalis 4 stations, while Cymodocea rotundata is only found at 2 stations, and Cymodocea serrulata at 1 station. The distribution and species composition also shows that the seagrass beds in Tunda Island are in a healthy category.

Schemes of multi-parameter stations in the Okhotsk Sea made in research cruises of TINRO (1984–2019)

Spatial distribution of stations made by research expeditions of TINRO in the Okhotsk Sea in 1984–2019 (82 surveys) is considered. The schemes of stations are sorted by decades, years, seasons, and months. Information the number of daylight and nighttime stations and the stations distribution by time of day, years, seasons, and by 33 biostatistical areas is presented in table form, that allows to estimate the data coverage at regional and temporal levels.

Strong Ground-Motion Characteristics Observed in the November 12, 2017, Mw7.3 Sarpol-e Zahab, Iran Earthquake

ABSTRACT The November 12, 2017, moment magnitude (Mw) 7.3 Sarpol-e Zahab earthquake, which occurred after a seismic quiescence, close to the Iran–Iraq border, is one of the largest events recorded in the Zagros fold and thrust belt. In this study, we analyzed strong-motion data of this event from 38 stations within an epicentral distance of 36 to 200 km. Spectral analysis of strong-motion data resulted in an Mw estimate of 7.34, an average rupture velocity of 3.03 km/s, and a stress drop of 154 bars. We estimated that shear dislocation propagated over a rectangular fault area with a length of ~97 km and width of ~17 km. Comparison of the horizontal peak ground-motions from this earthquake with the ground-motion model for active crustal regions indicated overall good agreement; however, the model underestimates ground-motions at stations within distances of approximately 30 km or less. The model appears to underestimate the observed strong-motion recordings from the Mw7.4 September 16, 1978, Tabas and the Mw7.4 June 20, 1990, Manjil earthquakes as well. Investigation of the observed accelerograms showed that the Sarpol-e Zahab earthquake was nucleated by a sub-event with a local magnitude (ML) of 4.9 which contributed about 0.02% to the total seismic moment. The empirical data indicated multiple arrivals due to the development of the rupture as two major sub-events. The spatial distribution of stations along with the time difference between the sub-events on the recorded time-series implies their occurrence from the hypocenter toward the S-SE direction which is coincident with the principal directions of the majority of damaged buildings. The estimated Mw of these sub-events is 6.79 and 7.08, respectively. The distinctive characteristics of near-field recordings from Sarpol-e Zahab earthquake (e.g., multiple phase arrivals due to complex source process, forward directivity effect, and blind thrust faulting) make these data a valuable supplement to the recorded ground-motion database. The improved strong-motion database plays a fundamental role in calibrating seismological simulation models, developing ground-motion models that capture near-source effects, and performing nonlinear dynamic structural analyses.

PREGRIDBAL 1.0: towards a high-resolution rainfall atlas for the Balearic Islands (1950–2009)

Abstract. This work presents a catalog of daily precipitation fields in the Balearic Islands created with data from AEMET (State Meteorological Agency) assistant observations, including records from 1912. The original digital daily data file has been interpolated onto a regular 100 m-resolution grid (namely PREGRIDBAL), defined with the aim of becoming a valid standard for future methodological improvements and catalog upgrades. Daily precipitation amounts on each grid point are calculated using an analysis method based on ordinary kriging, using the daily anomaly with respect to the annual mean for all available observations each day. Due to quality concerns, the time span for products derived from the catalog is limited to the 1950–2009 period, when the number of operating stations reached 200. Therefore, from the time series of daily maps, monthly-, annual-, quinquennial-, and decadal-accumulations are produced. Similarly, the catalog allowed for quantification of climate trends in rainfall amounts in the Balearic Islands, with the significant advantage of minimizing the biases originated from heterogeneities in the spatial distribution of stations across the archipelago. Results show a general decrease in precipitation during the 1950–2009 period. From 1950 to 1979, the average annual precipitation across the islands was 624.3 mm, while from 1980 to 2009 it diminished to 555.36 mm. Changes in precipitation patterns, which vary among the different areas, are also detected. The most significant reductions are found in the northern half of the archipelago and especially in Mallorca, where the Tramuntana mountain range stands out. All seasonal trends show a decrease, with values ranging between 1 and 3 mm decade−1, with the exception of autumn, which reaches a positive trend up to 7 mm decade−1. October shows the most dramatic decrease (−10. 34 mm decade−1) and, conversely, September and November show an increase in precipitation (3.28 and 1.82 mm decade−1, respectively) with a statistical significance above 85 % across almost the entire archipelago, and even exceeding 95 % in Eivissa and Formentera.

Space‐time tradeoffs in the development of precipitation‐based isoscape models for determining migratory origin

Precipitation stable isotope patterns over continental scales provide a fundamental tool for tracking origins of migratory species. Hydrogen isotopes from rain and environmental waters are assimilated into animal tissues and may thereby reveal the location where tissues were synthesized. Predictive isotopic maps (or isoscapes) of stable hydrogen isotope values in precipitation (δ2Hp) are typically generated by time‐averaging observations from a global network of stations that have been sampled irregularly in space and time. We previously demonstrated that restricting the temporal range in δ2Hp isoscapes to biologically relevant time frames did not improve predictions of geographic origin for two migratory species in North America and Europe; rather, it decreased the accuracy of assignment. Here, we examined whether the reduction in assignment accuracy stemmed from a decrease in the number of sampling stations available to support isoscape development for shorter time periods. Multiple regression models were used to predict the hydrogen isotope composition in precipitation using isotopic measurements from each station along with a suite of independent variables. The reduction in the number of stations with δ2Hp measurements used to estimate isoscape model parameters did not alter the accuracy and precision of assignments consistently. We also examined accuracy across a range of reduced station numbers and found that mean accuracy was affected only at very low numbers of stations, indicating that the spatial isotopic patterns in precipitation that are useful for assignment applications can be characterized with data from relatively limited data stations. The number and spatial distribution of stations may have more influence when geostatistical models are used to generate isoscapes, as they incorporate spatial correlation in the dataset. The results can be used to guide future research in understanding how data availability and constraints in creating δ2Hp isoscapes may affect predictions of geographic origins.

Trend analysis of winter rainfall over southern Québec and new Brunswick (Canada)

Winter rainfall is a non‐negligible issue for urban drainage in Canada as it can generate significant flooding, especially when it occurs at the same time as high air temperature and in the presence of an appreciable snow cover. According to climate change scenarios, it is expected that the occurrence of these events will increase in a future climate. The purpose of this paper is to perform a trend analysis on six indices related to winter rainfall (January–February) at 60 weather stations located in southern Québec and New Brunswick (Canada) in order to detect possible trends in the frequency or intensity of winter rainfall events during the twentieth century. Datasets were provided by Environment Canada and come from the Canadian Daily Rehabilitated Precipitation Database. The bootstrap‐based Mann‐Kendall test is used to detect possible non‐stationarities in the dataset, while Sen's slope estimator is used to quantify the magnitude of the slope. Results show that 19 stations out of 60 present a significant trend (18 of them being positive) at a 5% level for winter (January–February) total rainfall. In most cases where a trend was detected for winter rainfall there was also an increase in the number of days with rainfall (42% of the stations). These results suggest that globally, for the region under study, rainfall during January and February was more likely to occur, often resulting in a significant increase in the total rainfall during these months. Increasing trends in maximum daily rainfall during January and February were also observed for 9 stations (15% of the stations). The spatial distribution of stations where significant trends were detected is consistent with the hypothesis that trends in winter rainfall are more likely to be observed for stations located in the southern part of the region under study.

Optimal spatial distribution of seismic stations in mines

A procedure is developed for obtaining the optimal spatial distribution of seismic stations in mines. The optimality criterion is derived from the theory of optimal experiment. An optimal seismic network is one such that the spatial distribution of the stations with respect to the hypocenter position of the seismic event gives the best possible precision for the hypocenter parameters. The approach allows, when needed, to take into consideration: (i) different probability of event occurrence at different mining areas; (ii) planning for the best estimates of selected parameter as for example epicenter coordinates; (iii) building a network that is optimal for location of seismic events within a specified range of seismic energy. Four applications, two hypothetical and two in actual mines in Canada and in South Africa, respectively, show that the proposed procedure for optimal distribution of seismic stations provides a powerful and useful tool.

Optimizing the Global Observational Network: A Dynamical Approach

Abstract The global observational network is known to be highly inhomogeneous and fractally distributed in space. In this paper the spatial distribution of stations in a network is studied in connection with the type of dynamics exhibited by the atmospheric fields. The existence of an optimal distribution capable of capturing the complexity of this dynamics with a small prescribed error, and the role of deviations of the network distribution from a homogeneous one in this observational error are explored. For sparsely distributed stations like those of the present-day network, it is found that inhomogeneous distributions may generate a record that is closer to reality than homogeneous ones.

A comparative evaluation of principal components-based and information theory methods of precipitation regionalization

Precipitation regionalization techniques alternatively advocated by Johnston [15] and Willmott [30] are reviewed and compared. An implementation by Johnston [15] of the information theory or entropy method was determined to have limited applicability —principally owing to its inability (1) to describe periodicies that are inherent in the seasonal cycle and (2) to account for differences between time-series of precipitation with respect to their means. The entropy method, however, has a practical appeal because the spatial distribution of stations has a relatively minor, deleterious impact on the regionalization [15]. On the other hand, the principal components-based procedure described by Willmott [30] includes more information about precipitation in the evaluation of regional patterns, e.g., station means, and it is well-able to characterize periodicities in the variance. With the appropriate experimental design, the combination of principal components analysis and grouping is regarded as superior to the entropy method in identifying and characterizing precipitation regimes and regions.

COMPARATIVE EXAMINATION ON CRITERIA IN THE SYNOPTIC CLIMATOLOGICAL ANALYSES

In the so-called synoptic climatological analyses, it is a common approach to note both the frequency of occurrence of the type defined by a criterion or criteria, and the frequency of occurrence of element under the type. It may be, however, also a synoptic climatological approach to note both the frequency of the type and the average condition of element under the type. The methodology comes from the assumption that the types or items of a criterion or criteria may respectively correspond in the latter approach to different average onditions of element. In case of a climatologically better criterion or criteria in the latter approach, average conditions corresponding to the items may be discriminated one another at more broadly distributing, and more stations in a region. That is, the superiority of criteria may depend upon the number and the spatial distribution of stations, at which averages of element corresponding to the items are different one ano-ther. In this investigation the author tried with regard to some criteria to examine the superiority for synoptic climatological analyses of winter temperatures (i. e., daily maximum and minimum temperatures and diurnal range of temperature) in the Plains of Kanto, Central Japan. Data of temperatures were taken for three months (December, January and February) since 1961 to 1964, nine months in all, at seventy-eight stations almost evenly distributing in the Plains of Kanto. The above mentioned superiority was examined regarding the following four criteria: (a) surface pressure patterns in Far East at 00 GMT (Japan standard time, at 9 a, m.) (Yoshino and Kai, 1974), (b) contour line patterns at 700 mb level in East Asia at 00 GMT (Hohgetsu, 1975), (c) eight and (d) sixteen compass point directions of 700 mb level wind observed at 00 GMT at Tateno Aerological Observatory (36°03N, 140°08E), at which direction may approximately represent those in the Plains of Kanto. Referring to the relative occurrence frequencies of the patterns and the directions of the wind (Table 1), an analysis was done with regard to the following items in the criteria: winter monsoon type, trough type and migratory high type in (a) criterion, I (the southernmost location of 3, 000 gpm contour line between 100°E and 170°E is west of 130°E), fl (between 130°E and 150°E) and IIj (east of 150°E) in (b) criterion, NW, W and SW in (c) criterion and NW, WNW, W and WSW in (d) criterion. In this investigation the four criteria taken up in advance are compared one another. So multivariate statistical methods such as principal component analysis, canonical corre-lation analysis or factor analysis are not valid for the purpose of this investigation. Asmentioned before, averages of element corresponding to items of the climatologically superior' criterion may be discriminated one another at more, and more broadly distributing stations. So in this investigation the following method was taken to exa-mine the superiority: With regard to each criterion data of temperatures at each station were divided into groups, which were taken for probability samples, based on the above mentioned items, and then with regard to respective stations each combination of the groups was tested by F and “student-t” tests to examine whether a mean of a population, from which the group was taken, in ase of one item is significantly different from those in cases of the other items. Then the numbers and the spatial distributions of stations, where “student-t” test is significant, were compared one another to find the climatologically superior criterion. In this investigation, it was assumed that temperatures have normal distributions, respectively. Criteria (a) and (b) are equivalent to J level in Jacobs' scheme (1946, 1947) (Fig. 1), and (c) and (d) are also equivalent to F level.

Time variance of seismic velocity from multiple explosive sources southeast of Hollister, California

abstract As part of an intensive effort to monitor the section of the San Andreas fault south of Hollister, California, for any seismic velocity time variance associated with earthquakes, 17 explosive charges were fired between August 1974 and May 1975, at a point 35 km east of the fault zone and recorded by a special network of 51 seismometers within and west of the San Andreas fault zone. The shot point was selected to minimize differences in rock properties for successive shot locations, and all the data were recorded on a single tape recorder dedicated to the experiment. By cross-correlating the records from successive shots, it was possible to determine differential travel times to an accuracy of 4 msec or better using a 250-kg explosive charge recorded in the distance range between 30 to 50 km. No definitive changes in seismic velocity were detected during the time covered by this experiment. The spatial distribution of stations and the temporal distribution of shots were designed to reveal anomalies that might be associated with a magnitude 4 or greater earthquake. Nine small earthquakes (M = 2.9 to 3.3) did occur during the experiment, but anomalies associated with these earthquakes could have escaped detection. This work demonstrates the feasibility of monitoring large regions with a high density of instruments to detect systematic changes in arrival times from artifical sources with an accuracy approaching 1 msec and a cost commensurate with the task of earthquake prediction.