• Atmosphere
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• v.22 no.1
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• pp.117-128
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• 2012

Does snow depth initialization have a quantitative impact on sub-seasonal to seasonal prediction skill? To answer this question, a snow depth initialization technique for seasonal forecast system has been implemented and the impact of the initialization on the seasonal forecast of surface air temperature during the wintertime is examined. Since the snow depth observation can not be directly used in the model simulation due to the large systematic bias and much smaller model variability, an anomaly rescaling method to the snow depth initialization is applied. Snow depth in the model is initialized by adding a rescaled snow depth observation anomaly to the model snow depth climatology. A suite of seasonal forecast is performed for each year in recent 12 years (1999-2010) with and without the snow depth initialization to evaluate the performance of the developed technique. The results show that the seasonal forecast of surface air temperature over East Asian region sensitively depends on the initial snow depth anomaly over the region. However, the sensitivity shows large differences for different timing of the initialization and forecast lead time. Especially, the snow depth anomaly initialized in the late winter (Mar. 1) is the most effective in modulating the surface air temperature anomaly after one month. The real predictability gained by the snow depth initialization is also examined from the comparison with observation. The gain of the real predictability is generally small except for the forecasting experiment in the early winter (Nov. 1), which shows some skillful forecasts. Implications of these results and future directions for further development are discussed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.2
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• pp.212-220
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• 2015

We examined the appearance of cold water in the southwest region of the East Sea, based on the sea surface temperature (SST) at the east coast of Korea and buoy data in Donghae ($37^{\circ}31$'N, $130^{\circ}00$'E, 80 km east away from Donghae port) and Pohang ($36^{\circ}21$'N, $129^{\circ}46$'E, 35 km east away from Ganggu port) from June to August in 2013. Also, the serial oceanographic data of National Fisheries Research and Development Institute (NFRDI) were used to see the oceanographic conditions for June and August in 2013. The SST anomaly at the east coast showed negative values in $3{\sim}6^{\circ}C$ from 2 July. At Janggigab, the SST anomaly showed negative value amount to $10^{\circ}C$ in 8 July. The negative values of SST anomaly continued to the middle of August at Janggigab. The wind speed was 6~11 m/s and the direction was south-southwestly in 1 July. The wind speed amounts to 6~16 m/s in 2 July. It means that the strong wind induced the upwelling effect by a day. The temperature was lower than normal at the depth in 20 m of the East Sea in June and August. The air pressure was 996~998 hPa in the beginning of July. It was the lowest air pressure during the studied period. The correlation was 0.3 between the SST anomaly and air pressure. It was suggested that the appearance of cold water in the East Sea was influenced by a stirring due to wind and low air pressure as well as coastal upwelling.

• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.1
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• pp.55-62
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• 2006

Correlations between air-temperature variation and SST variation around Jeju Island have been studied with data JRMO($1924{\sim}2004$) and NFRDI($l971{\sim}2000$). Air-temperature has increased about $0.02^{circ}C/year$ for the period of $1924{\sim}2004$ but relatively high 0.035/year for the last 30 years. SST has increased about $0.024^{circ}C/year$ for the period of $1971{\sim}2000$ and relatively high $0.047^{circ}C/year$ in December. According to the analysis of time series of the two kind of variation, the SST and air-temperature are positively correlated. They are generally in phase, and SST anomaly is similar to air-temperature anomaly as well. Consequently, SST variation has high correlation with air-temperature variation around Jeju Island.

• Journal of Korean Institute of Architectural Sustainable Environment and Building Systems
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• v.12 no.6
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• pp.579-590
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• 2018

Anomaly detection on building energy consumption has been regarded as an effective tool to reduce energy saving on building operation and maintenance. However, it requires energy model and FDD expert for quantitative model approach or large amount of training data for qualitative/history data approach. Both method needs additional time and labors. This study propose a machine learning and data science approach to define faulty conditions on hourly building energy consumption with reducing data amount and input requirement. It suggests an application of Support Vector Data Description (SVDD) method on training normal condition of hourly building energy consumption incorporated with hourly outdoor air temperature and time integer in a week, 168 data points and identifying hourly abnormal condition in the next day. The result shows the developed model has a better performance when the ${\nu}$ (probability of error in the training set) is 0.05 and ${\gamma}$ (radius of hyper plane) 0.2. The model accuracy to identify anomaly operation ranges from 70% (10% increase anomaly) to 95% (20% decrease anomaly) for daily total (24 hours) and from 80% (10% decrease anomaly) to 10%(15% increase anomaly) for occupied hours, respectively.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• v.21 no.1
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• pp.47-54
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• 1993

The major positive sea surface temperature(SST) anomalies not only occur in the region with the most moisture increase, but also in the flank of the area with sinking motion in the Subtropics. As the large amount of water vapor has been increased by the SST anomaly, the increased of the SST is expected to destabilize the air and leads under moist adiabatic unstable conditions, to an enhanced development of moisture cluster. The 4.0 K change of SST causes the positive difference of Brightness Temperature(TB) of about 10.0k for water vapor channels of TOVS over the north eastern and central tropical Pacific Ocean, but the negative difference of TB of about 7.5 K is shifted southward and southeastward to Southern Pacific Ocean along the equator correspondingly. The difference of the TBs for IR water vapor channel $11(7.3{\mu}m)$ and $12(6.7{\mu}m)$ of TOVS indicative of the moisture distribution during two time periods(January 1983 and 1984), leads us to infer significant changes in the entire tropospheric circulations and the dynamic processes over the Pacific Ocean.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• v.26 no.1
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• pp.31-41
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• 1998

The climatic characteristics of summer in 1998 are analyzed with the weather observational data and the upper air observational data. The temperature of that period is lower than that of normal years and the precipitation is larger. Due to the heavy rainfall which started at July 31, rain pured down compared to normal years and the maximum precipitation recorded at the many observational stations, particularly in Seoul, Kyunggi-Do region and mountanious districts like Taegwallyong, Mt. Sokri and Mt. Chiri. The patterns of general circulations in 1982/98 and 1997/98 are compared each other and are analyzed. The anomaly patterns of stream functions on winter in two El Nio years are simialr. The counterclockwise circulation occurred near the date line and the clockwise circulation was appeared near the Hwanam region and Alaska. These patterns are opposite to those of La Nia year, 1988/89. And the anomaly patterns of 500hPa geopotential height in summer are similar, too. The low temperature and much rain were dominated in summer of 1997/98. These phenomena is similar to the existing results of research, that temperature is low and precipitation is large in summer of El Nio years.

• Atmosphere
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• v.31 no.1
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• pp.61-71
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• 2021

The relationship between the Arctic Oscillation (AO) and surface air temperature (SAT) over Korea is re-examined using the long-term observation and reanalysis datasets for the period of December 1958 to February 2020. Over the entire period, Korean SAT is positively correlated with the AO index with a statistically significant correlation coefficient, greater than 0.4, only in the boreal winter. It is found that this correlation is not static but changes on the decadal time scale. While the 15-year moving correlations are as high as 0.6 in 1980s and 1990s, they are smaller than 0.3 in the other decades. It is revealed that this decadal variation is partly due to the AO structure change over the North Pacific. In the period of 1980s-1990s, the AO-related sea level pressure fluctuation is strong and well defined over the western North Pacific and the related temperature advection effectively changes the winter SAT over Korea. In the other periods, the AO-related circulation anomaly is either weak or mostly confined within the central North Pacific. This result suggests that Korean SAT-AO index relationship, which becomes insignificant in recent decades is highly dependent on mean flow change in the North Pacific.

• Journal of the Korean Geographical Society
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• v.43 no.5
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• pp.701-714
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• 2008

This study examines the prevailing synoptic-scale mechanisms favorable for long-lived summer Persistent Positive Temperature Anomalies (PPTAs) as well as winter PPTAs in the United States. Such long-lived PPTAs usually occur in the south-central region of the United States in summer, but in the southwestern part of the United States in winter. Composite analyses of surface and pressure level data demonstrate that the formation of both winter and summer PPTAs is closely related to the movement of subtropical high pressure systems in the Pacific Ocean and Atlantic Ocean, respectively. The occurrence of long-lived summer PPTAs usually coincides with an extremely stable atmospheric condition caused by persistent blocking by mid- to upper-tropospheric anticyclones. Significant surface forcing is also easily identified through relatively high Bowen ratios at the surface. Warm air advection is, however, weak and appears to be an insignificant element in the formation of long-lived summer PPTAs. On the other hand, synergistic warming effects associated with adiabatic heating under an anticyclonic blocking system as well as significant warm air advection characterize the favorable synoptic environments for long-lived winter PPTAs. However, the impact of surface forcing mechanisms on winter PPTAs is insignificant.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.992-996
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• 2008

In this study, changes in precipitation across South Korea during snow seasons (November-April) and their potential are examined. Current (1973/74-2006/07) and future (2081-2100) time series of snow indices including snow season, snow-to-precipitation ratio, and snow impossible day are extracted from observed snow and precipitation data for 61 weather stations as well as observed and modeled daily temperature data. Analyses of linear trends reveal that snow seasons have shortened by 3-13 days/decade; that the snow-to-precipitation ratio (the percentage of snow days relative to precipitation days) has decreased by 4-8 %/decade. These changes are associated with pronounced formations of a positive pressure anomaly core over East Asia during the positive Arctic Oscillation winter years since the late 1980s. A snow-temperature statistical model demonstrates that the warming due to the positive core winter intensifies changes from snow to rain at the rate of $4.7cm/^{\circ}C$. The high pressure anomaly pattern has also contributed to decreases of air-sea thermal gradient which are associated with the reduction of snow could formation. Modeled data predict that a fingerprint of wintertime global warming causing changes from snow to rain will continue to be observed over the 21st century.

• Atmosphere
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• v.22 no.4
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• pp.465-472
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• 2012

Using various observed data, we examined the evolution of tropical Pacific sea surface temperature (SST) during 2011-2012, with focusing on the development of 2012 El Ni$\tilde{n}$o. It is observed that a La Ni$\tilde{n}$a event during 2011 was followed by a moderate El Ni$\tilde{n}$o during 2012 summer. The 2012 summer El Ni$\tilde{n}$o initiated near the west coast of South America on February 2012, and continued to expand westward till August. Given this evolutionary pattern, the 2012 summer El Ni$\tilde{n}$o can be categorized as 'Eastern Pacific (EP) El Ni$\tilde{n}$o' because Ni$\tilde{n}$o-3 index is greater than Ni$\tilde{n}$o-4 index, and it may be the first well-defined EP El Ni$\tilde{n}$o since 2001. On February 2012, this event was initiated mainly by the local air-sea interaction, and at the same time the ocean heat content was accumulated over the tropical western Pacific due to the easterly wind anomaly over the tropical western Pacific. Then, the accumulated heat content slowly propagates to the tropical eastern Pacific, which attributes to maintain El Ni$\tilde{n}$o state during 2012 summer. After August, the positive SST anomaly over the equatorial eastern Pacific decays possibly due to the exhausted heat content and the weakening of air-sea interaction, but the weak positive SST anomaly over the central Pacific remains till now (2012 November).