• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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• pp.154-154
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• 2018

To interpret the climate projections for the future as well as present, recognition of the consequences of the climate internal variability and quantification its uncertainty play a vital role. The Korean Peninsula belongs to the Far East Asian Monsoon region and its rainfall characteristics are very complex from time and space perspective. Its internal variability is expected to be large, but this variability has not been completely investigated to date especially using models of high temporal resolutions. Due to coarse spatial and temporal resolutions of General Circulation Models (GCM) projections, several studies adopted dynamic and statistical downscaling approaches to infer meterological forcing from climate change projections at local spatial scales and fine temporal resolutions. In this study, stochastic downscaling methodology was adopted to downscale daily GCM resolutions to hourly time scale using an hourly weather generator, the Advanced WEather GENerator (AWE-GEN). After extracting factors of change from the GCM realizations, these were applied to the climatic statistics inferred from historical observations to re-evaluate parameters of the weather generator. The re-parameterized generator yields hourly time series which can be considered to be representative of future climate conditions. Further, 30 ensemble members of hourly precipitation were generated for each selected station to quantify uncertainty. Spatial map was generated to visualize as separated zones formed through K-means cluster algorithm which region is more inconsistent as compared to the climatological norm or in which region the probability of occurrence of the extremes event is high. The results showed that the stations located near the coastal regions are more uncertain as compared to inland regions. Such information will be ultimately helpful for planning future adaptation and mitigation measures against extreme events.

• 한국지구과학회지
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• 제38권3호
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• pp.182-193
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• 2017

A typical snowfall pattern occurs over the east coastal region of the Korean Peninsula, known as the Yeongdong region. The precipitation over the Yeongdong region is influenced by the cold and dry northeasterly wind which advects over warm and moist sea surface of the East Sea of Korea. This study reveals the influence of large-scale factors, affecting local to remote areas, on the mesoscale snowfall system over the Yeongdong region. The National Centers for Environmental Prediction-Department of Energy reanalysis dataset, Extended Reconstructed sea surface temperature, and observed snowfall data are analyzed to reveal the relationship between February snowfall and large-scale factors from 1981 to 2014. The Yeongdong snowfall is associated with the sea level pressure patterns over the Gaema Plateau and North Pacific near the Bering Sea, which is remotely associated to the sea surface temperature (SST) variability over the North Pacific. It is presented that the relationship between the Yeongdong snowfall and large-scale factors is strengthened after 1999 when the central north Pacific has warm anomalous SST. These enhanced relationships explain the atmospheric patterns of recent strong snowfall years (2010, 2011, and 2014). It is suggested that the newly defined index in this study based on related SST variability can be used for a seasonal predictor of the Yeongdong snowfall with 2-month leading.

• Ocean and Polar Research
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• 제23권4호
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• pp.361-376
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• 2001

The characteristics of SST variability in the East Sea are analyzed using NOAA/AVHRR weekly SST data with about $0.18^{\circ}{\times}0.18^{\circ}$ resolution ($1981{\sim}2000$) and reconstructed historical monthly SST data with $2^{\circ}{\times}2^{\circ}$ resolution $(1950{\sim}1998)$. The distinct feature of wintertime SST is high variability in the western and eastern parts of $38^{\circ}{\sim}40^{\circ}$ latitudinal band, which are the northern boundary of warm current in the East Sea during winter. However, summertime SST exhibits variability with similar magnitude in the entire region of the East Sea. The analysis of remote correlation also shows that SST in the East Sea is closely correlated with that in the region of Kuroshio in winter, but in summer is related with that in the western and eastern regions of the same latitudes. From these results it is postulated that the SST variability in the East Sea may be related with the variations of East Korean Warm Current and Tsushima Warm Current in winter, but in summer probably with the variations of atmospheric components. In the analysis of ENSO related SST anomaly, a significant negative correlation between SST anomalies in the East Sea and SST anomalies in the tropical Pacific is found in the months of August-October (ASO). The SST in the ASO period shows more significant cooling in E1 $Ni\~{n}o$ events than warming in La $Ni\~{n}a$ events. Also, the regional analysis shows by the Student's t-test that the negative SST anomalies in the E1 $Ni\~{n}o$ events are more significant in the southwestern part of the East Sea.

• Ocean and Polar Research
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• 제39권3호
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• pp.169-179
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• 2017

The "GeoDrifter" is a newly-developed surface drifter with high temporal resolution. It is the first time that high-frequency drifters have been deployed in the East/Japan Sea. The purpose of this study is to introduce the phenomena experienced by these drifters flowing along with the Tsushima Current across the East/Japan Sea, focusing on high-frequency variability, and to discuss them in comparison with previous observations. The observed basin-scale circulation of the Tsushima Current generally coincides well with the known schematic circulation. The GeoDrifter trajectories also show inertial oscillations almost everywhere in the oceanic regions of the East/Japan Sea, strong semi-diurnal tidal currents in the western part of Korea Strait, diurnal currents much stronger than semi-diurnal currents in the upstream region of the Nearshore Branch off the Japanese coast, and many warm eddies in the Yamato Basin, all comparable to the observational results reported in the previous studies. An interesting point is that the semi-diurnal tidal currents undergo a great spatial variation in the western part of the Korea Strait. The observed features that cannot be explained are, among others, strong counter-clockwise motions with oscillating period about 51 hours appearing in the upstream region of the Nearshore Branch off the Japanese coast and the different tidal behaviors between upstream and downstream regions of the latter.

• The Plant Pathology Journal
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• 제35권3호
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• pp.243-256
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• 2019

Field surveys for Plum pox virus (PPV) infection were conducted in stone fruit orchards all over Bulgaria. In total, 1168 out of 3020 leaf samples from cultivated Prunus spp. and wildly growing P. cerasifera trees reacted positive for PPV in DASI-ELISA with the universal monoclonal antibody (MAb) 5B. Further ELISA analyses showed that 987 and 127 isolates belonged to PPV-M and PPV-D serotypes, respectively. The plum and P. cerasifera showed 82.0% and 50.5% levels of infection, respectively followed by the peach (40.0%) and the apricot (32.0%). Five hundred fifty one PPV isolates were further typed by IC-RT-PCR with PPV-Rec, -M and -D-specific primers, targeting (Cter)NIb-(Nter) CP genome region, as 125 isolates were sequenced. The results revealed the presence of PPV-Rec, PPV-M and PPV-D and mixed infections of these strains. PPV-Rec was the most prevalent strain (49.0%), followed by PPV-M (40.1%), while PPV-D was the less spread strain (8.2%). PPV-Rec was the most common strain in plums, including the eight "old-aged" trees from the region of the first Sharka discovery. PPV-M was the most prevalent strain in peach and apricot. Phylogenetic analyses on (Cter)NIb-(Nter)CP of the isolates were performed. PPV-Rec isolates formed a homogeneous group, while PPV-M isolates split into PPV-Ma and PPV-Mb subgroups. Five separated clades were formed by the analyzed PPV-D isolates. Nucleotide sequences of the partial CP coding region of the analyzed isolates revealed a slightly higher intra-strain genetic variability in PPV-Rec and PPV-M isolates, while that of PPV-D strain isolates was higher from the reported for these strains.

• 한국기후변화학회지
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• 제6권2호
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• pp.95-104
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• 2015

To discuss whether we have credible estimations about historical surface temperature evolution since industrial revolution or not, present study investigates consistencies and differences of averaged surface air temperature since 1900 between the multiple data sources: Hadley Center Climate Research Unit (HadCRU4) surface air temperature data, ECMWF 20 Century Reanalysis data (ERA20CR), and NCEP 20 Century Reanalysis data (NCEP20CR). Averaged surface temperatures are obtained for the global, polar (90S~60S, 60N~0N), midlatitude (60S~30S, 30N~60N), tropical (30S~30N) region, separately. From the analysis, we show that: 1) spatio-temporal inhomogenity and scarcity of HadCRU4 data are not major obstacles in the reliable estimation of global surface air temperature. 2) Globally averaged temperature variability is largely contributed by those of tropical and midlatitude, which occupy more than 70% of earth surface in area. 3) Both data show consistent temperature variability in tropical region. 4) ERA20CR does not capture warm period over Arctic region in early 1900s, which is obvious feature in HadCRU4 data. Discrepancies among datasets suggest that high-level caution is needed especially in the interpretation of large Arctic warming in the early 1900s, which is often regarded as a natural variability in the Arctic region.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1296-1305
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• 2008

In this study, the spatial distribution of depth between alluvial soil and weathered soil of Song-do new city is analyzed using geostatistics. From analysis results, the boundary depth of north-east region is deeper than that of south-west region, and average depth of north-east region is 27.14m and average depth of south-west region is 23.25m. The boundary depth is estimated by ordinary kriging and inverse distance method, and estimated results are almost similarity. So, in Song-do new city, these two method can be used to estimate the boundary depth. The ordinary kriging method is a very useful tool because the more exact analysis of spatial continuity and distribution characteristic is possible.

• 천문학회보
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• 제41권2호
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• pp.64.2-64.2
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• 2016

Optical variability is one way to probe the nature of the central engine of AGN at smaller linear scales and previous studies have shown that optical variability is more prevalent at longer timescales and at shorter wavelengths. Especially, intra-night variability can be explained through the damped random walk model but small samples and inhomogeneous data have made constraining this model hard. To understand the properties and physical mechanism of optical variability, we are performing the KMTNet Active Nuclei Variability Survey (KANVaS). Test data of KMTNet in the COSMOS field was obtained over 2 separate nights during 2015, in B, V, R, and I bands. Each night was composed of 5 and 9 epochs with ~30 min cadence. To find AGN in the COSMOS field, we applied multi-wavelength selection methods. Different selection methods means we are looking different region in unification model of AGN, and 100~120, 400~500, 50~100 number of AGN are detected in X-ray, mid-infrared, and radio selection of AGN, respectively. We performed image convolution to reflect seeing fluctuation, then differential photometry between the selected AGN and nearby stars to achieve photometric uncertainty ~0.01mag. We employed one of the standard time-series analysis tools to identify variable AGN, chi-square test. Preliminarily results indicate that intra-night variability is found for X-ray selected, Type1 AGN are 23.6%, 26.4%, 21.3% and 20.7% in the B, V, R, and I band, respectively. The majority of the identified variable AGN are classified as Type 1 AGN, with only a handful of Type 2 AGN showing evidence for variability. The work done so far confirms that there are type and wavelength dependence of intra-night optical variability of AGN.

• Journal of Astronomy and Space Sciences
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• 제33권3호
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• pp.177-183
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• 2016

Active galactic nuclei (AGN) are too compact to be resolved by any existing optical telescope facility, making it difficult to understand their structure and the emission processes responsible for their huge energy output. However, variability, one of their characteristic properties, provides a tool to probe the inner regions of AGN. Blazars are the best candidates for such a study, and hence a considerable amount of effort is being made to investigate variability in these sources across the electromagnetic spectrum. Here, using the Mt. Abu infrared observatory (MIRO) blazar monitoring program, we present intra-night, inter-night, and long term aspects of the variability in S5 0716+71, 3C66A, and OJ 287. These stars show significant variability on short (a few tens of mins, to a few hours, to a few days) to long term (months to years) timescales. Based on the light travel time argument, the shortest variability timescales (micro-variability) provide upper limits to the size of the emission region. While S5 0716 shows a very high duty cycle of variability (> 80 %), 3C66A shows a much lower intra day variability (IDV) duty cycle (< 20 %). All three show rapid variations within 2.5 to 3.5 hr, which, perhaps, are generated near the vicinity of black holes. Assuming this, estimates of the masses of the black holes are made at ~10⁹, 8×10⁸, and 2.7×10⁹ M_⨀ for S5 0716+71, 3C66A, and OJ 287, respectively. Multi-wavelength light-curves for the blazar PKS 1510-089 are discussed to infer the emission processes responsible for the recent flaring episodes in this source.

• 천문학회보
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• 제42권1호
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• pp.39.2-39.2
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• 2017

Stars form through the gravitational collapse of molecular clouds. However, the rate at which a star gains most of its mass and the physics that drives the main phase of stellar growth is still unclear. The typical luminosity of observed protostars is smaller than what expected from the Shu's inside-out collapse model, which predicts a constant mass accretion rate. The episodic accretion model has been suggested as a solution of this luminosity problem. The JCMT Transient survey is a long term monitoring program using JCMT/SCUBA-2 to detect accretion variability of protostars in the eight nearby star-forming regions. Recently, we found a rise of the 850 micron flux at a clump in the Serpens main region at the rate of ~17% relative to the mean flux over previous observations. The submm clump is associated with a class I protostar, EC53, which has been reported as a binary system with a periodic variability. In this talk, we will provide a brief overview of the JCMT Transient Survey project, present the detection of the variable source, and discuss about follow-up observations.