A case study on synoptic analysis using the Korea Analysis System (KAS) to enhance severe weather monitoring over the Korean Peninsula

The occurrence of severe weather events has shown increasing frequency and intensity due to global climate change. The Korean Peninsula, characterized by complex inland orography and surrounded by seas on three sides, exhibits diverse meteorological phenomena significantly influenced by seasonal wind regimes. While forecasters traditionally analyze synoptic conditions using locally available observations, the irregular spatial and temporal distribution of these observations limits their ability to conduct comprehensive three-dimensional analyses. Furthermore, although global model analysis fields have been widely used for operational forecasting, their coarse spatial and temporal resolutions constrain the real-time analysis of localized severe weather events. To address these limitations and enhance nowcasting capabilities, the Korea Meteorological Administration (KMA) has implemented the Korea Analysis System (KAS) since May 2024, a real-time analysis system that utilizes a high-resolution regional model to provide rapid updates of current atmospheric conditions essential for monitoring and predicting mesoscale weather phenomena.

This study evaluates KAS's effectiveness in reproducing real-time atmospheric phenomena and its practical utility for severe weather analysis through extensive synoptic case studies. KAS generates hourly three-dimensional nowcast analysis fields at 3 km resolution by integrating 15 categories of synoptic and non-synoptic observational data with the operational Korean Integrated Model-regional (KIM-regional) forecast fields, assimilating observations up to 15 minutes past each hour to provide near real-time atmospheric conditions. The system demonstrated remarkable capability in capturing critical meteorological features across various weather regimes. During summer, KAS effectively identified precursors of convective precipitation by analyzing real-time low-level convergence zones, dewpoint depression fields, high equivalent potential temperature areas, and vertical p-velocity distributions. The system's skew T-log P diagrams revealed significant Convective Available Potential Energy (CAPE) values, providing quantitative measures of atmospheric instability and potential for convective cloud development and subsequent precipitation in specific regions. In winter scenarios, KAS accurately depicted strong wind variations, including northwesterly cold air flows and easterly winds associated with orographic precipitation. Notably, the system's thermal advection analysis fields effectively identified regions of warm air advection and their interaction with cold air masses, providing crucial indicators for potential snowfall accumulation zones, particularly in areas where warm maritime air masses encounter pre-existing cold air.

The results validate KAS's capability to provide forecasters with coherent three-dimensional nowcast analyses, overcoming the limitations of traditional forecasting methods based on irregularly distributed observations and coarse-resolution global model analyses. This advancement establishes a foundation for improved real-time severe weather detection and forecast accuracy across the Korean Peninsula and East Asia region.

Acknowledgement: This work was supported by Development of Numerical Weather Prediction and Data Application Techniques (KMA2018-00721).