In this study, we analyzed the intraseasonal variability and change of winter temperature over South Korea using long-term observations. The lowest temperature in the wintertime, using daily mean, maximum, and minimum temperature data occurred on January 7th in the period of 2003~2012, while on January 22~25th in the past 30 years(1973~1982, 1983~1992, 1993~2002). Representative seven stations in South Korea also showed consistent result. The strengthening of Siberian High and weakening of Aleutian Low in recent 10 years are found to be closely related with the recent intraseasonal temperature change over South Korea. The baroclinic structure of upper-level low and lower-level high system near Korean peninsula provided good condition for vertical cold-air advection, which resulted in minimum temperature on late January in 1973~1982 and early January in 2003~2012 with strengthened low-level northerly flow.
We found that, in 1984, there was a climate regime shift in April mean precipitation in Gwangju of Jeollanam-do province, Korea using a statistical change-point analysis. During the period of post-1984(1985-2013), the April mean precipitation in the years post-1984 showed a distinct decrease, compared to the pre-1984 period(1954-1984). This regime shift was also observed in China and Japan, excluding southern China. One of the major causes for the decreasing April mean precipitation during the recent three decades was the increased snow depth in the mid-latitude regions of continental East Asia. The increased snow depth resulted in strengthened cold and dry anticyclone anomaly over continental East Asia and a relatively weakened subtropical anticyclone anomaly over the western North Pacific. The anomalous synoptic conditious supported a continuation of the typical winter pressure pattern of ‘high-West and low-East’ over East Asia in April. The intensified northerly winds from this zonal pressure pattern anomaly played a significant role in restricting the northern movement of the subtropical anticyclone and there by preventing the inflow of warm and humid air into Korea.
˜e purpose of this study is to identify the characteristic synoptic patterns of the spring (March to May) heavy rainfall events over Mt. Halla by the approach type of the warm conveyor belts around migratory extratropical cyclones. Analyses of synoptic atmospheric conditions show that the spring warm conveyor belts in the form of low-level jets appear at lower elevation than that in summer. Most of spring heavy rainfall events over Mt. Halla at the warning stages or watch result from forward-sloping ascent warm conveyors belts accompanying active convection. Particularly, the spring heavy rainfall events at the warning level over Mt. Halla is intensified by the elongation of the foreward-sloping ascent warm conveyor belts when the east high-west low pressure systems, the upper level jet in the northern region- southwesterly low level jet and the migratory low pressure system at mature stage heading for the Korean Peninsular are combined. These findings can be used in improving the predictability of the spring heavy rainfall events over Mt. Halla.
This study was aimed to investigate the relationship between flood damage and rainfall in the downstream areas of Han River. We used flooding damage and daily rainfall data observed in the 12 downstream areas during 2000-2012. Rainfall variables were analysed which include total rainfall over the basin of downstream areas in the Han River for flooding periods, maximum accumulative rainfall over 1hours, 3 hours, 6 hours and 12 hours, and rainfall in the upper regions of the Han River. Flooding damages of the study areas have signiÿcant positive correlations with rainfall variables. The most significant variable that affect the amount of damage is 3 hour accumulative precipitation. It means that the more three-hour precipitation increases, the more the amount of damage also increases. We found that there is a high possibility of floods when a heavy rainfall day continues for more than 2 days by comparing heavy rainfall days between with and without flooding disasters. The possibility of flood decreases when interval of just before a heavy rainfall day and flooding period increase.
This study investigates the theoretical background of the interpolation methods that regards the topographical effect on the climate data, such as Co-kriging, Artificial Neural Network and MK-PRISM(Modified Korean Parameter-elevation Regressions on Independent Slopes Model). Prior to applying the MK-PRISM to the interpolation of wind speed, this study has improved the model to be closer to the fundamental concept of the PRISM and verified it‘s validity. Since each method has individual advantages and disadvantages, there will be a need for comparative studies in order to select an interpolation method that is suitable for the topography of Korea. This study has added a weighted value that considers the existence of clusters at the known point, and has supplemented the digital elevation models and aspects distribution of multiple scales for application. In addition, this study has allowed the consideration of sharp changes between the known point and unknown point when calculating the topographic facet weighting. The supplement model was verified through the interpolation of rainfall in Jeju Island. The coefficient of determination and KGE(Kling and Gupta Efficiency) of the model displayed the results of 0.86 and 0.87, respectively for August 2010 monthly precipitation in Jeju Island, and the model was accordingly verified. This study is able to provide the necessary information to the researchers who wish to interpolate the observation data of wind speed. Furthermore, the supplement MK-PRISM becomes available to the research on the interpolation of wind speed.
In this study, instead of economic estimation of forecast value, we evaluated the value score(VS) of the user satisfaction using the concept of satisfaction/dissatisfaction. We compared the collective Value Scores (cVS) based on outputs of probabilistic forecasts of precipitation seasonally in Seoul and Busan during the period of 2004 to 2013 and ÿnally found the optimum threshold that can improve cVS of both cities. When using 30% threshold, the users can expect a higher cVS compared with those using other thresholds. When using the seasonal optimum threshold in Seoul, the cVS is additionally higher by 9%. These results show the level of satisfaction of the forecast that can be improved when the meteorological communities inform the users the correct threshold of the rainfall probabilistic forecast.