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The earth system model (ESM) mostly provides an output of hydrological variables at a daily scale, such as precipitation. Finer temporal scale data of precipitation is required for assessing the impact of climate change on floods, especially in small-size urban and mountainous watersheds which are vulnerable to floods. This study enhanced population-based nonparametric temporal downscaling (PNTD) to downscale daily precipitation to 10-min precipitation (P10M), and tested it in the Jinju area, South Korea, that includes both urban and mountainous areas. Results indicated that the enhanced PNTD model reproduced the key statistics of the P10M data and the statistical characteristics of extreme events represented by the annual maximum precipitation (AMP) series of different durations. Also, the daily precipitation of 19 ESMs with the base and future scenarios, called shared socio-economic pathways, for 245 and 585 conditions were applied and downscaled to P10M data. It was found that the future P10M precipitation scenarios were downscaled satisfactorily by preserving the difference between base and future scenarios of the AMP data. Also, results showed that the uncertainty from ESMs was about 10 times larger than from temporal downscaling and it indicated that the uncertainty in temporal downscaling can be acceptable. The P10M data can be employed for deriving intensity–duration–frequency curves needed for designing urban drainage systems and other hydraulic and hydrologic structures and for installing flood warning systems. [ABSTRACT FROM AUTHOR]

This study was conducted to examine the correlation between the South Asian High (SAH) shift and the summer (June-August) rainfall variability in Korea over the course of 45 years (1958-2002). It is found that the shift in the west-east direction is closely related to the summer rainfall variability in Korea. The atmospheric circulations in the east shift years showed that at 850 hPa, an intensification of the western North Pacific subtropical high allowed a sufficient amount of warm and humid air to be supplied to the lower atmosphere near Korea. On the other hand at 200 hPa, the SAH expanded toward the east, near the southern part of Korea, causing the intensification of the northwesterlies, and this allowed the supply of cold and dry air to the upper atmosphere near Korea. Meanwhile, in the latitudinal zone in which Korea is located, there were anomalous upward flows with warm and humid characteristics in the lower atmosphere and anomalous downward flows with cold and dry characteristics in the upper atmosphere. As such, the cold and warm air masses present in the upper and lower atmosphere near Korea led to thermal instability, and this was analyzed to be a major factor that could potentially increase the amount rainfall in Korea in summer in the east shift years. Moreover, a warm SST anomaly was formed in the mid-latitude zones of East Asia, and it heated the lower troposphere, thereby intensifying the thermal instability even further. Furthermore, TCs frequently had an impact on Korea in the east shift years, and were another factor that caused the increased rainfall in summer. [ABSTRACT FROM AUTHOR]

We investigate the multi-decadal variability of observed surface wind speed around South Korea. It is found that surface wind speed exhibits decreasing trend from mid-1950s until 2003, which is similar with the trends reported for other parts of the world. However, the decreasing trend ceases and becomes unclear since then. It is revealed that decreasing wind speed until 2003 is strongly associated with the decreasing trend of the spatial variance in both atmospheric pressure and air temperature across the East Asia for the same period. On the contrary, break of decreasing trend in surface wind speed since 2003 is associated with increasing spatial variance in surface temperature over the East Asia. Ground observation shows that surface wind speed and air temperature exhibit highly negative correlations for both summer and winter prior to 2003. However, since 2003, the correlations differ between seasons. We suggest that mechanisms behind the recent wind speed trend are different between summer and winter. This is on the basis of an interesting finding that air temperature has decreased while surface temperature has increased during winter months since 2003. We hypothesize that such contrasting temperature trends indicate more frequent movement of external cold air mass into the region since 2003. We also hypothesize that increasing summer wind speed is driven by intrusion of warm air mass into the region which is witnessed via increasing spatial variance in surface temperature across East Asia and the fact that both air and surface temperature rise together. [ABSTRACT FROM AUTHOR]

An analysis of simulated future surface climate change over the southern half of Korean Peninsula using a RegCM3-based high-resolution one-way double-nested system is presented. Changes in mean climate as well as the frequency and intensity of extreme climate events are discussed for the 30-year-period of 2021–2050 with respect to the reference period of 1971–2000 based on the IPCC SRES B2 emission scenario. Warming in the range of 1–4°C is found throughout the analysis region and in all seasons. The warming is maximum in the higher latitudes of the South Korean Peninsula and in the cold season. A large reduction in snow depth is projected in response to the increase of winter minimum temperature induced by the greenhouse warming. The change in precipitation shows a distinct seasonal variation and a substantial regional variability. In particular, we find a large increase of wintertime precipitation over Korea, especially in the upslope side of major mountain systems. Summer precipitation increases over the northern part of South Korea and decreases over the southern regions, indicating regional diversity. The precipitation change also shows marked intraseasonal variations throughout the monsoon season. The temperature change shows a positive trend throughout 2021–2050 while the precipitation change is characterized by pronounced interdecadal variations. The PDF of the daily temperature is shifted towards higher values and is somewhat narrower in the scenario run than the reference one. The number of frost days decreases markedly and the number of hot days increases. The regional distribution of heavy precipitation (over 80 mm/day) changes considerably, indicating changes in flood vulnerable regions. The climate change signal shows pronounced fine scale signal over Korea, indicating the need of high-resolution climate simulations [ABSTRACT FROM AUTHOR]