Enhanced Calibration Assessment of Chinese Ground-based Polarimetric Radars Using a Refined GPM DPR Volume-matching Method

Accurate calibration of China’s new generation ground-based polarimetric radar (GR) network is crucial yet challenging. Despite the application of the Global Precipitation Measurement Core Observatory’s Dual-frequency Precipitation Radar (GPM DPR) for GR assessment is well-established, current methodologies suffer from inherent limitations. Focusing on three GRs in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA), strategically selected for their high overlapping coverage (>65%) and distinct from single GR or less dense coverage studies, this work introduces key refinements by integrating innovative enhancements into the volume-matching method (VMM), reflecting a systematic approach to mitigating potential error sources. Specifically, we integrate: 1) a novel frequency correction method adaptive to DPR-observed precipitation phase and type, replacing assumption-based polynomial fitting; and 2) a precise beam time-difference matching approach (accuracy < 1s) to minimize temporal mismatch errors, improving upon coarser time averaging. Furthermore, systematic sensitivity analyses evaluating 11 quality control factors like precipitation type, bright band effects, and attenuation correction limitations informed the development of statistically robust, optimized threshold criteria. These criteria establish an enhanced protocol designed to minimize errors arising from instrumental, frequency, and scanning differences. Applying this enhanced methodology to the GBA GRs (2021–2023) yielded significantly improved matching accuracy (Correlation Coefficient, CC: 0.90–0.95; Standard Deviation, STD: 1.2–1.6 dB). A unique contribution is the quantitative estimation of historical calibration errors and operational stability achieved by linking VMM results with operational GR calibration and maintenance records. This analysis revealed decreasing STD trends and identified specific calibration-related events, such as a potential ~2.43 dB underestimation identified for the Shenzhen radar following its 2023 calibration. Consequently, the refined methodology provides a robust framework for ongoing GR network monitoring and offers a validated pathway for the authenticity verification of China’s Fengyun-3G (FY-3G) satellite precipitation measurement radar (PMR) data.