Abstract. On 2 August 2020, a coastal bow-echo mesoscale convective system (MCS) produced severe rainfall and damaging winds over South Korea, resulting in casualties and property losses. Forecasting rapidly developing coastal bow echoes remains challenging due to limited understanding of the interactions between mesoscale dynamics and microphysical processes. Here, we analyze these interactions using improved multi-Doppler wind retrievals and polarimetric radar observations. The system evolved into a leading convective–trailing stratiform structure, reinforced by a rear-inflow jet (RIJ) that enhanced low-level convergence and shaped bowing segments. Feedbacks between RIJ-driven downdrafts, convective updrafts, and hydrometeor recycling sustained precipitation and prolonged the system’s lifetime after landfall. In particular, mixed-phase hydrometeors in stratiform clouds were advected into the leading convective line, where they enhanced and maintained deep convection. These dynamic–microphysical interactions governed storm organization and rainfall efficiency, explaining the persistence of heavy precipitation in the coastal zone. Beyond advancing process understanding, our results highlight the role of land–sea contrasts in shaping mesoscale circulations that intensify convection and provide observational benchmarks for improving forecasts and hazard resilience in coastal regions.

This study presents an comprehensive evaluation of Geostationary Environment Monitoring Spectrometer (GEMS) ozone products using daily ozonesonde data measured during the Asian Summer Monsoon Chemical and Climate Impact Project (ACCLIP). The analysis uses a total of 38 ozonesonde measurements along with atmospheric reanalysis to better understand ozone variability and circulation impacts during the Asian summer monsoon. It shows significant variability of tropospheric and lower stratospheric ozone related to convective activities associated with the Asian monsoon rainband and strong anticyclone in the upper troposphere and lower stratosphere (a.k.a. Tibet high). The comparison of the ozonesonde data and GEMS ozone products reveals GEMS’s capability to capture these variabilities, and also highlights its potential utility in the studies of chemical transport and regional-scale air quality in Asia.

This study presents a case-based evaluation of Geostationary Environment Monitoring Spectrometer (GEMS) ozone products using daily ozonesonde measurements during pre-ACCLIP (2021) and ACCLIP (2022) campaigns. The analysis uses a total of 62 ozonesonde profiles along with atmospheric reanalysis to better understand daily ozone variability and circulation change related to the Asian summer monsoon. The new GEMS ozone profile (version 3) product successfully captures significant variability in tropospheric and lower stratospheric ozone, including major stratospheric ozone intrusion in 2021 and storm-induced tropospheric ozone decreases in 2022. These variations were closely related to convective activities associated with the Asian monsoon rainband and strong anticyclones in the upper troposphere and lower stratosphere. The comparison between ozonesonde data and GEMS ozone products demonstrates GEMS's capability to detect these dynamic ozone variations, highlighting its potential in monitoring chemical transport and regional-scale air quality in Asia.

This study investigates an ozone intrusion event observed during the Pre-Asian Summer Monsoon Chemical and Climate Impact Project in August 2021, using 26 consecutive daily ozonesonde measurements over South Korea. A pronounced enhancement in total column ozone was observed between 17 and 19 August, which can be largely attributed to an ozone intrusion in the upper troposphere-lower stratosphere (UTLS), accounting for approximately 60% of the increase. The upper tropospheric circulation patterns demonstrate a clear signature of anticyclonic Rossby wave breaking (AWB) on the northeastern edge of the Asian summer monsoon anticyclone, aligned with the summertime jet stream. This AWB, accompanied by a cut-off low and tropopause folding, facilitated downward transport of stratospheric ozone into the upper troposphere. In addition, the ozone variability is investigated in two chemical reanalysis data sets: Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) and European Centre for Medium-Range Weather Forecasts (ECMWF) Atmospheric Composition Reanalysis 4 (EAC4). MERRA-2 and EAC4 capture the ozone intrusion event with relevant synoptic-scale circulation patterns and ozone variability. However, discrepancies of ozone data in the chemical reanalyses were found in vertical ozone structures and persistence in the troposphere. MERRA-2 better represented the secondary ozone peak in the UTLS but underestimated lower-tropospheric ozone. In contrast, EAC4 showed a systematic positive bias particularly in the stratosphere and near the surface. Continued integration of temporally high-resolution ozone measurements is beneficial for understanding synoptic-scale ozone variability and evaluating emerging chemical reanalyses.

Background: High-fidelity meteorological data is a prerequisite for the realistic simulation of atmospheric dispersion of radioactive materials near nuclear power plants (NPPs). However, many meteorological models frequently overestimate near-surface wind speeds, failing to repre-sent local meteorological conditions near NPPs. This study presents a new high-resolution (ap-proximately 1 km) meteorological downscaling method for modeling short-range (< 100 km) atmospheric dispersion of accidental NPP plumes. Materials and Methods: Six considerations from literature reviews have been suggested for a new dynamic downscaling method. The dynamic downscaling method is developed based on the Weather Research and Forecasting (WRF) model version 3.6.1, applying high-resolution land-use and topography data. In addition, a new subgrid-scale topographic drag parameter-ization has been implemented for a realistic representation of the atmospheric surface-layer mo-mentum transfer. Finally, a year-long simulation for the Kori and Wolsong NPPs, located in southeastern coastal areas, has been made for 2016 and evaluated against operational surface meteorological measurements and the NPPs' on-site weather stations. Results and Discussion: The new dynamic downscaling method can represent multiscale at-mospheric motions from the synoptic to the boundary-layer scales and produce three-dimen-sional local meteorological fields near the NPPs with a 1.2 km grid resolution. Comparing the year-long simulation against the measurements showed a salient improvement in simulating near-surface wind fields by reducing the root mean square error of approximately 1 m/s. Fur-thermore, the improved wind field simulation led to a better agreement in the Eulerian estimate of the local atmospheric dispersion. The new subgrid-scale topographic drag parameterization was essential for improved performance, suggesting the importance of the subgrid-scale mo-mentum interactions in the atmospheric surface layer. Conclusion: A new dynamic downscaling method has been developed to produce high -reso-lution local meteorological fields around the Kori and Wolsong NPPs, which can be used in short-range atmospheric dispersion modeling near the NPPs.

To establish a strategy for public protective action from radioactive leakage in the event of Nuclear Power Plant (NPP) accidents, long-term records of wind data collected at the Korean NPPs were analyzed. Wind characteristics related to the advection and diffusion of radioactive pollutants were examined by analyzing the wind direction, speed, and land-sea breezes for NPPs (Hanbit, Hanul, Wolsong, Kori, and Shin-Kori) in Korea. The study also analyzed the characteristics of calm winds causing the accumulation of radioactive materials. The wind characteristics of each NPP differ depending on the seasonal and daily variabilities; thus, a detailed time-scaled airflow database is required. In addition, the findings, through continuous updates of the airflow database, will contribute to improving preparedness.

In this study, we examined a spatial downscaling method based on Gradient and Inverse Distance Squared (GIDS) weighting to produce high-resolution grid data from a numerical weather prediction model over Korean Peninsula with complex terrain. The GIDS is a simple and effective geostatistical downscaling method using horizontal distance gradients and an elevation. The predicted meteorological variables (e.g., temperature and 3-hr accumulated rainfall amount) from the Limited-area ENsemble prediction System (LENS; horizontal grid spacing of 3 km) are used for the GIDS to produce a higher horizontal resolution (1.5 km) data set. The obtained results were compared to those from the bilinear interpolation. The GIDS effectively produced high-resolution gridded data for temperature with the continuous spatial distribution and high dependence on topography. The results showed a better agreement with the observation by increasing a searching radius from 10 to 30 km. However, the GIDS showed relatively lower performance for the precipitation variable. Although the GIDS has a significant efficiency in producing a higher resolution gridded temperature data, it requires further study to be applied for rainfall events.

A millimetre-wave cloud radar has limitations for observing heavy rainfall because the short wavelength leads to strong attenuation from raindrops. However, recent studies have attempted to estimate the rain rate using attenuation, which becomes greater as the rain intensity increases. The rain-rate-retrieval algorithm is developed in the present paper using the Ka-band cloud radar (KaCR) installed at the Boseong Global Standard Observatory (BGSO) in the Republic of Korea. First, rain profiles were identified using the threshold of reflectivity (Z) and Doppler velocity (DV) averaged for the analysis of layer that minimized the effects of the receiver saturation and classified as low or high rain-rate cases using the averaged DV. The reflectivity and rain-rate (Z-R) relationship was then derived for low rain-rate cases that showed insignificant effects for signal attenuation. On the other hand, the attenuation and rain-rate (A-R) relationship was derived using high rain-rate cases that showed the dominant effects of attenuation. The attenuation was calculated using a reflectivity gradient between the upper and lower boundaries of the attenuated layer. Finally, the rain-rate-retrieval algorithm was designed using the derived Z-R and A-R relationship and then applied back to the KaCR. The estimated rain rate in the KaCR was a similar trend to the observed rain rate in the optical rain gauge (ORG), but slightly underestimated.

기상청에서는 초단기 강수예보를 위해 초단기예측시스템(VDAPS)과 강수실황모델(MAPLE)을 현업 운영하고 있다. 두 모델의 강수예측성능은 실황으로부터 3시간 예측까지는 MAPLE이 VDAPS보다 높지만 그 이후 예측시간에는 VDAPS가 MAPLE보다 높다. 이 연구에서는 초단기 강수예측성능을 개선하고자 마이크로 유전알고리즘을 이용하여 두 모델의 장점을 결합하여 실황과 초단기 예측의 이음새 없는 강수예측을 도출하였다. 마이크로 유전알고리즘은 두 모델의 결합을 위한 반영 가중치 추정을 위해 사용되었으며, 1시간부터 6시간 예측까지의 예측시간에 따른 가중치를 추정하는 실험과 강수의 공간적인 분포를 고려한 예측시간별, 공간별 가중치를 추정하는 실험을 수행하였다. 두 실험에서 추정한 가중치는 1, 2시간 예측에서 MAPLE이 컸고 그 이후의 예측에서는 VDAPS가 컸다. 또한 초단기 강수예측성능 개선 여부 확인을 위해 훈련기간과 예측기간에 대해 강수임계값별 예측성능을 검증하였다. VDAPS와 MAPLE을 결합한 실험의 결과에서 두 모델의 예측특성중 장점만이 결합되어 1, 2 시간의 강수예측성능은 높고 그 이후의 시간에서 VDAPS의 예측성능보다 높게 유지하여 실황과 초단기 예측의 이음새 없는 강수예측이 도출됨을 확인하였다.

ABSTRACT Cloud microphysical variables are needed to evaluate and improve cloud parameterization and data assimilation in a numerical weather model. In order to obtain high spatiotemporal resolution data for the cloud, data from the Ka‐band cloud radar (KaCR), an instrument specialized for cloud observation, were used. In this study, the liquid water content (LWC) was estimated, and the reflectivity–liquid water content ( Z –LWC) relationships were derived using the vertical profiles of radar reflectivity from the KaCR and the liquid water path (LWP) from a microwave radiometer. The data were collected at the Boseong National Center for Intensive Observation of Severe Weather in the Republic of Korea during an intensive observation period in 2014 (2014‐IOP, 16 June to 15 July 2014). First, the KaCR reflectivity was corrected using the linear depolarization ratio from the KaCR. The process also involved removing reflectivity profiles that have signal attenuation, compared with the cloud‐top heights retrieved from a satellite. The LWC profiles were calculated from the LWP by dividing using the weight of the KaCR reflectivity. Different constants were derived from the Z –LWC relationship according to each respective echo type. Therefore, the KaCR echoes were categorized into non‐precipitating clouds, precipitating clouds, and raindrops, using a micro rain radar and a ceilometer. The Z –LWC relationships were finally derived for each categorized echo. The results of this study suggest that the new method should be useful for retrieving cloud microphysical variables. These relationships allowed the estimation of 3D LWC in high resolution using a single KaCR platform.

On 10 July 2014, tornado outbreak occurred over Goyang province in Korea. This was the first supercell tornado ever reported or documented in Korea. The characteristics of the supercell tornado were investigated using an X-band polarimetric radar, surface meteorological observation, wind profiler, and operational numerical weather prediction (Regional Data Assimilation and Prediction System, RDAPS). The supercell tornado developed along a preexisting dryline that was contributed to surface wind shear. The radar analyses examined here show that the supercell tornado indicated a hook echo with mesocyclone. The decending reflectivity core as well was detected before tornadogenesis and prior to intensification of supercell. The supercell tornado exhibited characteristics similar to typical supercell tornado over the Great Plains of the United States, such as hook echo, bounded weak echo region, and slower movement speed relative to the mean wind. Compared to the typical supercell tornado over U.S., this tornado showed horizontal scale of the mesocyclone was relatively smaller and left-mover.

In this study,cloud base height(CBH) and cloud top height(CTH) observed by the Ka-band(33.44 GHz) cloud radar at the Boseong National Center for Intensive Observation of Severe Weather during fall 2013(September-November) were verified and corrected.For comparative verification,CBH and CTH were obtained using a ceilometer(CL51) and the Communication,Ocean and Meteorological Satellite(COMS).During rainfall,the CBH and CTH observed by the cloud radar were lower than observed by the ceilometer and COMS because of signal attenuation due to raindrops,and this difference increased with rainfall intensity.During dry periods,however,the CBH and CTH observed by the cloud radar,ceilometer,and COMS were similar.Thin and low-density clouds were observed more effectively by the cloud radar compared with the ceilometer and COMS.In cases of rainfall or missing cloud radar data,the ceilometer and COMS data were proven effective in correcting or compensating the cloud radar data.These corrected cloud data were used to classify cloud types,which revealed that low clouds occurred most frequently.

This study provides a comparative analysis of cloud top heights observed by a Ka-band cloud radar and the Communication, Ocean and Meteorological Satellite (COMS) at Boseong National Center for Intensive Observation of severe weather (NCIO) from May 25, 2013 (1600 UTC) to May 27. The rainfall duration is defined as the period of rainfall from start to finish, and the no rainfall duration is defined as the period other than the rainfall duration. As a result of the comparative analysis, the cloud top heights observed by the cloud radar have been estimated to be lower than that observed by the COMS for the rainfall duration due to the signal attenuation caused by raindrops. The stronger rainfall intensity gets, the more the difference grows. On the other hand, the cloud top heights observed by the cloud radar have been relatively similar to that observed by the COMS for the no rainfall duration. In this case, the cloud radar can effectively detect cloud top heights within the range of its observation. The COMS indicates the cloud top heights lower than the actual ones due to the upper thin clouds under the influence of ground sur-face temperature. As a result, the cloud radar can be useful in detecting cloud top heights when there are no precipitation events. The COMS data can be used to correct the cloud top heights when the radar gets beyond the valid range of observation or there are precipitation events.

In contrast to the normal seasons that are classified by the distribution of temperature and precipitation, this study defines a new concept of the water abundant season (WAS) when water is more abundant than in other seasons. We investigated its characteristics on 60 stations in Korea, and compared it with Changma (the rainy season). In this study, Available Water Resources Index (AWRI), which is a summed daily precipitation accumulated for more than 365 days with a time-dependent reduction function and reflects the current water condition, was used to quantify the water amount. In addition, the median value of 30 year’s daily AWRI was used as the criterion value dividing WAS from other seasons. The results show that the terminologies on water resources have changed from qualitative concepts such as abundance, deficit, and continuous rainfall, to quantitative values using AWRI. In detail, it was known that the WAS in Korea starts on 2 July and ends on 25 December, lasting for 176 days. The onset date of WAS in Korea is getting earlier, with a trend of 2.9 days/decade. The end date does later with a delay of 7.5 days/decade, and the duration is increasing at 10.4 days/decade. We looked at the WAS by stations and saw, on average, that 14 June was the earliest onset date in Seogwipo and 29 July was the latest one in Sokcho, representing a difference of 45 days. The earliest end date was in Tongyeong at 5 December and the latest one is in Uljin at 16 January of the following year, a difference of 41 days. Tongyeong had the shortest (166 days) WAS duration and Uljin had the longest (207 days) on average. The big spatial differences of the criterion values per station were detected and quantified. The largest criterion value for WAS were recorded in Seongsan with 270.7 mm, which is almost double of the smallest value, which was recorded in Uiseong (135.9 mm). Comparing WAS with the Changma (the rainy season in Korea) showed that the onset date of WAS is close to that of Changma, but the end date shows a big difference. It is also known that WAS was more useful than Changma in detecting and demonstrating both of the season’s progress and the seasonal state of water climates.

ABSTRACTThis study found a positive correlation between the August rainfall in North Korea and Antarctic Oscillation (AAO) in August. Causes of increasing rainfall in the positive AAO phase are (1) the increasing frequency of tropical cyclones that land in or affect the Korean Peninsula, (2) the reinforcement of Australian high (AH) in the Southern Hemisphere, and (3) atmospheric instability at all levels in August in North Korea. The reinforcement of AH forms an anomalous cross‐equatorial flow in the western Pacific and plays a decisive role in the northward development of the subtropical western North Pacific high (SWNPH). Furthermore, large volumes of warm and humid air are supplied to North Korea owing to this development. As a result, atmosphere in North Korea becomes unstable, and it is found that the reinforcement of anomalous warm sea surface temperature (SST) in the middle latitude of East Asia is another cause of the instability.

The characteristics of the drought occurrence in North Korea over a period of 56 years (1952–2007) were analyzed by region, compared with those of South Korea, and graphed as a drought map for easy detection of the drought’s history. To assess them, the Effective Drought Index (EDI), which was calculated from the daily precipitation data for 109 grids of the Korean Peninsula, was used. The daily precipitation data were extracted from the Asian Precipitation Highly Resolved Observational Data Integration towards Evaluation of Water Resources (APHRODITE). The characteristics of the drought occurrence in North Korea were summed up in the following five points. First, North Korea was divided into four drought sub-regions: the Northeastern region (G1), the Northern region (G2), the Central region (G3), and the Southern region (G4). Second, droughts occurred most frequently in G1 (28) and G4 (28 events) and least frequently in G3 (15 events). Third, in all sub-regions, short-term droughts lasting less than 100 days were the most frequent (53 % or higher) and the longest drought lasted 2,911 days (June 30, 1973 to June 20, 1981), which occurred in G3. Fourth, short-term droughts occurred mainly in spring, mid-term droughts (100–500 days) in spring and summer, and long-term droughts (over 500 days) in summer. Fifth, a dry period (monthly mean EDI <0) appeared in all sub-regions between 1973 and 1981 and between 1990 and 1993, and a strong negative precipitation anomaly appeared during each of these periods. When compared to the droughts in South Korea, those in North Korea were less frequent, but the mean duration was longer. Until 1979, droughts occurred almost at the same time in North Korea as South Korea, but beginning in 1980, the time differences between two regions became larger. Thus, the characteristics of the drought occurrence in North and South Korea differ.