Fine-scale evolutionary characteristics of Super Typhoon Doksuri (2023) revealed by multi-source observations

The variations in the track and intensity of a tropical cyclone (TC) are closely correlated with the fine-scale evolution of its structure. The fine-scale track, intensity, and structural evolution of TC can be comprehensively analyzed by combining multi-source observations. Based on observations from space-borne synthetic aperture radars (SARs), the Advanced Microwave Scanning Radiometer-2 (AMSR2), the Special Sensor Microwave Imager/Sounder (SSMIS), weather radars, in-situ buoys and island stations, an analysis was conducted on the fine-scale evolutionary characteristics of high-impact Super Typhoon Doksuri (2023). The results show that Doksuri (2023) experienced secondary eyewall formation (SEF), concentric eyewall maintenance (CEM), and eyewall replacement cycle (ERC) processes when entering the South China Sea and prior to landfall. These processes can be further delineated into three subsequent stages. In the first stage, the SEF phase, the secondary (outer) eyewall formed, exhibiting features that were non-concentric with the inner eyewall. Concurrently, the track of Doksuri (2023) displayed notable oscillations in both its forward translational direction and speed, accompanied by the emergence of two radial maxima centers of wind speed. Subsequently, during the second stage, the CEM phase, the geometric centers of the inner and outer eyewalls of Doksuri (2023) coincided, initiating a rapid intensification process characterized by an accelerated forward translational speed. Both the inner and outer eyewalls further contracted during this phase. In the third stage, the ERC phase, the asymmetry of the inner eyewall increased, and the outer eyewall gradually contracted while the inner eyewall dissipated until the replacement was completed prior to landfall. Accordingly, Doksuri (2023) experienced rapid weakening. With special attention been paid to the possible connection between the evolution of the typhoon structures and the changes in its track and intensity, it is found that the substantial track oscillations were closely associated with the asymmetric development of TC inner and outer eyewalls during the SEF, and, the rapid intensity changes were correlated with the CEM and ERC processes. These findings have the potential to enhance our understanding of the physical mechanisms governing the intricate structures of TCs at fine scales, bolstering the forecast accuracy of TC tracks and intensities.