• The Journal of the Acoustical Society of Korea
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• v.20 no.5
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• pp.92-99
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• 2001

To measure temporal variability of long- range transmission in northern part of the East Sea of Korea, low frequency acoustic sources were deployed on the continental shelf 0.4km south of Cape Shultz near the port of Vladivostok during October 1999. The transmissions of the phase modulated signals were recorded by VLA moored on the northern slope of Ulleung-do. The measured signals were processed for the acoustic arrivals and their variability in time. The temporal signal processing involves pulse compression of the phase-encoded signal, time spread and temporal coherence processing. Variability of the ocean sound speed field in time scales of short period seems to be dominated by random fluctuations caused by sound speed perturbation due to the vertical displacements associated with internal waves.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.434-436
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• 2005

Analysis method using remote sensing data is one of the effective ways to research a spatial and temporal variability of the mesoscale oceanic motions. During past several decades, many researchers have been getting comprehensive results using remote sensing data with application of data fusion methods in many parts of geo-science. For this study, we took the integration and fusion of several remote sensing data, which are different data resolution, timescale and characteristics, for improving accurate analysis of variation of the Kuroshio Extension. Furthermore, we might get advanced ways to understand the variability of the Kuroshio Extension, has close relation to the spatial and temporal variation of the Kuroshio and Oyashio Current.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3B
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• pp.285-293
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• 2010

Soil moisture is a key factor to control the exchange of water and energy between the surface and the atmosphere. In recent, many researches for spatial and temporal variability analyses of soil moisture have been conducted. In this study, we analyzed the spatio-temporal variability of soil moisture in Walnut Gulch Experimental Watershed, Arizona, U.S. during the Soil Moisture Experiment 2004 (SMEX04). The spatio-temporal variability analyses were performed to understand sensitivity of five observation sites with precipitation and relationship between mean soil moisture, and its standard deviation and coefficient of variation at the sites, respectively. It was identified that log-normal distribution was superior to replicate soil moisture spatial patterns. In addition, precipitation was identified as a key physical factor to understand spatio-temporal variability of soil moisure based on the temporal stability analysis. Based on current results, higher spatial variability was also observed which was agreed with the results of previous studies. The results from this study should be essential for improvement of the remotely sensed soil moisture retrieval algorithm.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.691-695
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• 2004

In recent years, mary studies for efact estimation of groudwater recharge has been performed. They can be categorized into three groups : analytical method by means of groundwater recession curve, water budget analysis based on watershed, and the method using groundwater model. Since groundwater recharge rate shows the spatial-temporal variability due to hydrogeological heterogeneity, existing studies have various limits to deal with these characteristics. The method of estimating daily recharge rate with spatial-temporal variation based on rainfall-runoff model is suggested in this study for this purpose. This method is expected to enhance existing indirect method by means of reflecting climatic conditions, land use and hydrogeological heterogeneity.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.3
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• pp.1-11
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• 2011

The temporal variability of spring (March, April, May) monthly precipitation, precipitation effectiveness, monthly maximum precipitation, monthly precipitation of different durations, and the precipitation days over several threshold (i.e. 0, 10, 20, 30, 40, and 50 mm/day) of 59 weather stations between 1973 and 2009 were analyzed. Also to analyze the regional characteristics of temporal variability, 59 weather stations were classified by elevations, latitudes, longitudes, river basins, inland or shore (east sea, south sea, west sea) area and the level of urbanization. Results demonstrated that trends of variables increase in April and decrease in May except precipitation day. Overall trend of precipitation amount and precipitation effectiveness is same but precipitation effectiveness of several sites decrease despite the trend of precipitation amount increases which may be caused by the air temperature increase. Therefore more effective water supply strategy is essential for Spring season. Regional characteristics of Spring precipitation variability can be summarized that increase trend during May become stronger with the increase of latitude and elevation which is similar to that of Summer season. The temporal variability of variables showed different behaviors according to river basins, inland or shore (east sea, south sea, west sea) area and the level of urbanization.

• Current Research on Agriculture and Life Sciences
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• v.32 no.4
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• pp.203-209
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• 2014

This study investigated characteristics of rainfall and water quality in Saemangeum area with attention to temporal and spatial distributions. A high variability in rainfall was noted during July and August. The temporal analysis of water quality data indicated that DO and TN as well as BOD, COD and SS were within national standards except for increased concentrations during spring and summer, unlike TP values that indicated poor water quality. Standard deviation showed a high variability in SS among the seasons most especially during summer. The high dispersion indicated variability in the chemical composition of pollutants where the temporal and spatial variations caused by polluting sources and/or seasonal changes were most evident for BOD and COD during winter and spring. The box plots and bar charts showed steadily low concentrations of BOD, COD, TN and TP except within Iksan and notable significant variations in SS concentrations among the monitoring stations. Thus, high pollution levels requiring intervention were identified in Mangyeong river basin with particular concern for areas represented by Iksan station. It was noted that Iksan received a considerable amount of rainfall which meant high runoff which could explain the significant pollution levels revealed in the water quality spatial distribution. Major pollution contributing pollutants within Saemangeum area were identified as SS, BOD, COD and TN. Therefore the present results could be used as a guideline for the temporal and spatial distributions analysis of both rainfall and water quality in Saemangeum watershed.

• Journal of Ship and Ocean Technology
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• v.8 no.2
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• pp.20-28
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• 2004

A dynamic-thermodynamic sea ice model with 50-km spatial and 24-hour temporal resolution is used to investigate the spatial and long-term temporal variability of the sea ice cover the Arctic Basin. The model satisfactorily reproduces the averaged main characteristics of the sea ice and the sea ice extent in the Arctic Basin and its decrease in early 1990th. At times model allows to suppose partial recovery of sea ice cover in the last years of twenty century. The employment of explicit form for description of ridging gives opportunity to assume that the observed thinning is the result of reduction the intensity of ridging processes and to estimate long-term variability of probability the ridge free navigation in the different parts of the Arctic Ocean including the North Sea Route area.

• Journal of the Korean earth science society
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• v.44 no.1
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• pp.1-12
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• 2023

Oceanic wind waves have been recognized as one of the important indicators of global warming and climate change. It is necessary to study the spatial and temporal variability of significant wave height (SWH) and wave direction in the Yellow Sea and a part of the East China Sea, which is directly affected by the East Asian monsoon and climate change. In this study, the spatial and temporal variability including seasonal and interannual variability of SWH and wave direction in the Yellow Sea and East China Sea were analyzed using European Center for Medium-Range Weather Forecasts (ECMWF) Reanalysis 5 (ERA5) data. Prior to analyzing the variability of SWH and wave direction using the model reanalysis, the accuracy was verified through comparison with SWH and wave direction measurements from Ieodo Ocean Science Station (I-ORS). The mean SWH ranged from 0.3 to 1.6 m, and was higher in the south than in the north and higher in the center of the Yellow Sea than in the coast. The standard deviation of the SWH also showed a pattern similar to the mean. In the Yellow Sea, SWH and wave direction showed clear seasonal variability. SWH was generally highest in winter and lowest in late spring or early summer. Due to the influence of the monsoon, the wave direction propagated mainly to the south in winter and to the north in summer. The seasonal variability of SWH showed predominant interannual variability with strong variability of annual amplitudes due to the influence of typhoons in summer.

• The Journal of the Acoustical Society of Korea
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• v.33 no.6
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• pp.413-419
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• 2014

Underwater acoustic channel has time-variability. Time varying channel which disturbs the continuous transmission of information data reduces the underwater acoustic communication performance. In this paper, we show the temporal coherence as time-variability of channel and indicate throughput efficiency in accordance with transmission time of information data. Then we analyzed influence of underwater channel time-variability on communication throughput efficiency. We confirmed that the throughput efficiency reduced when the time-variability of the channel increased via lake trial.

• Phonetics and Speech Sciences
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• v.9 no.4
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• pp.19-25
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• 2017

The current study focused on the production of geminate nasal consonants across different word boundary types in Korean as a function of speech style to investigate whether temporal properties are preserved across varying speaking rates. Assimilated geminates in Korean, known as true geminates, are produced with distinctively longer consonant duration compared to singletons. Despite a large body of literature for geminates across different languages, geminates in Korean have been relatively less investigated with respect to the durational patterns in relative terms and temporal variabilities. In this study, singletons, word-internal geminates and word-boundary (fake) geminates produced by ten native Seoul Korean speakers were compared in terms of absolute consonant closure duration, preceding vowel duration, the relative ratios (consonant-to-preceding vowel duration) as well as the temporal variabilities in speech production. The results showed that word-internal geminates were produced with longer consonant duration and greater temporal variabilities than singletons and word-boundary geminates in absolute duration, indicating relatively greater flexibility in timing. However, only word-internal geminates were produced with distinctively longer consonant duration with significantly lower variability in relative duration regardless of speech styles. The results provide some insight into the representation of temporal information in the production of Korean geminate consonants.