Tailoring TPTRS for Operational Thermodynamic Retrieval in the Complex Terrain of Korea

The Korea Meteorological Administration Weather Radar Center (WRC) has collaborated with Taiwan National Central University (NCU) and ported the multiple-Doppler radar wind field retrieval technique (WISSDOM) and thermodynamic variable retrieval technique. WISSDOM utilizes a variational method to overcome the limitations of conventional wind retrieval techniques. It determines the optimal wind vector from radial velocities of multiple weather radars through iterative calculations of control variables (horizontal and vertical wind components) to minimize the cost function of dynamic constraints. Consequently, WISSDOM produces a 3D wind field that satisfies the physical equations and reflects the influence of observational data. WRC has tuned the algorithm to suit the complex terrain of Korea, enabling real-time operation. As a next step, we aim to develop a radar wind field-based thermodynamic variable retrieval technique called the Terrain-Permitting Thermodynamic Retrieval Scheme (TPTRS). TPTRS retrieves thermodynamic variables such as pressure, temperature, and water vapor mixing ratio using a 3D wind field synthesized from multiple Doppler radars in complex terrain. To address the challenges posed by complex terrain, TPTRS applies the Immersed Boundary Method to constrain the flow of fluids on the ground and utilizes a cost function composed of momentum and thermodynamic equations. By iteratively minimizing the cost function, TPTRS retrieves significant 3D thermodynamic variables. In this study, we implemented a radar-based TPTRS algorithm suitable for the complex terrain of Korea and analyzed its results. We conducted experiments to determine the optimal number of iterations for real-time operation and obtained meaningful results with over 1000 iterations. A case study was conducted on a heavy rainfall event that occurred on 31 July 2019, analyzing the potential temperature, mixing ratio, and pressure fields. In the cross-section of the developing major precipitation system, we observed an increase in potential temperature with altitude, accompanied by high and thick mixing ratios. This aligns with the characteristics of a developing system and is considered a significant result. We plan to develop a system for retrieving thermodynamic variables across the entire Korean Peninsula in the future.

This research was supported by the " Development of radar based severe weather monitoring technology (KMA2021-03121)" of "Development of integrated application technology for Korea weather radar" project funded by the Weather Radar Center, Korea Meteorological Administration.