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Approximately, 25.6 tropical cyclones (TCs) occur in the western North Pacific (WNP) each year, of which 3.4 TCs affect the Korean Peninsula (KP). In 2019, a record of seven TCs affected the KP. We investigated and elucidated the favorable conditions influencing the TCs approaching the KP using the Weather Research and Forecasting model version 4.0 (WRFv4). The cold Maritime Continent‐warm WNP sea surface temperature (SST) was found to be a major factor. The effect of the SST gradient was examined for one representative case using WRFv4 with varying SST anomalies. This study suggests that the SST gradient‐induced change in the circulation over the Maritime Continent is a main factor causing the TCs to approach the KP.

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Conceptual models to analyze both typhoon and Changma using products extracted by the GEO-KOMPSAT-2A (GK-2A) are suggested in this study. The GK-2A which is scheduled to be launched in 2018 has a high resolution, 16 channels, and 52 products. This means GK-2A is expected to obtain high quality images and products, which can detect severe weather earlier than the Communications, Ocean and Meteorological Satellite (COMS). Since there are not enough conceptual models for typhoon and Changma using satellite images and products, our conceptual model can increase both the applicability of satellite data and the accuracy of analysis. In the conceptual model, typhoons are classified as three types by prevailing factors; 1) heavy-rainfall type, 2) wind type, and 3) complex type. For Changma, two types are divided by the characteristics; band type and heavy-rainfall type. Among the high resolution 52 products, each type of typhoon and Changma are selected. In addition, the numerical products and dynamic factors are considered in order to improve conceptual models.

Climate change has altered the frequency, intensity, and timing of mean and extreme precipitation. Extreme precipitation has caused tremendous socio-economic losses, and severe impacts on human life, livelihood, and ecosystems. In recent years, heavy rainfall events occurred during the boreal summer (June-to-August) frequently and sporadically over South Korea. Given that its severity, a call for an urgent investigation of summer extreme rainfall is needed. Although many previous studies have addressed daily extreme precipitation, hourly extreme rainfall still needs to be thoroughly investigated. Therefore, in this study, we investigated the trends, spatio-temporal variability, and long-term variations in mean and extreme precipitation over South Korea during the boreal summertime using daily and hourly observational data through various analysis methods. During the past 50 years , there has been a notable escalation in maximum hourly precipitation, although the boreal summer mean precipitation has increased only marginally. Regionally, an increase in mean and extreme rainfall occurred in the northern part of the central region and the southern coast of the Korean peninsula. Moreover, the increase in intensity and frequency of extreme precipitation as well as in dry day have contributed more to the total summer precipitation in recent years. Our findings provide scientific insights into the progression of extreme summer precipitation events in South Korea.

<p>Approximately, 25.6 tropical cyclones (TCs) occur in the western North Pacific (WNP) each year, of which 3.4 TCs affect the Korean Peninsula (KP). In 2019, a record of seven TCs affected the KP. We investigated and elucidated the favorable conditions influencing the TCs approaching the KP using the Weather Research and Forecasting model version 4.0 (WRFv4). The cold Maritime Continent-warm WNP sea surface temperature (SST) was found to be a major factor. The effect of the SST gradient was examined for one representative case using WRFv4 with varying SST anomalies. This study suggests that the SST gradient-induced change in the circulation over the Maritime Continent is a main factor causing the TCs to approach the KP.</p>

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