An insight into the microphysical attributes of northwest Pacific tropical cyclones (original) (raw)

Northwestern Pacific (NWP) tropical cyclones (TCs) impose a severe threat to the life and economy of the people living in East Asian countries. The microphysical features, mainly the raindrop size distributions (RSD) of TCs that improve the modeling simulation and rainfall estimation algorithms, are limited to case studies, and an extensive understanding of TCs' RSD is still scarce over the northwest Pacific. Here, we examine a comprehensive outlook on disparities in microphysical attributes of NWP TCs with radial distance and storm type, using sixteen years of disdrometer, ground-based radar, and reanalysis datasets in north Taiwan. We find that dominant stratiform precipitation in the inner rainbands leads to the occurrence of more bigger drops in the inner rainbands than the inner core and outer rainbands. Moreover, a decrease in mass-weighted mean diameter and rainfall rate with radial distance is associated with a reduction in moisture availability for various circumstances, and this association is deceptive in intense storms. Our findings give an insight into crucial processes governing microphysical inequalities in different regions of NWP TCs, with implications for the ground-based and remote-sensing rainfall estimation algorithms. The Northwestern Pacific (NWP) Tropical cyclones (TCs) (also called typhoons) associated with torrential rainfall attribute a severe threat to the life and economy of people living in East Asian countries 1-3 , and are accountable for floods and earth surface processes 4-7 , which emphasizes the significance of acquiring an enhanced understanding of rain and cloud microphysics of TCs for the accurate prediction of rainfall and intensity 8. The precipitation microphysics of TCs, especially the raindrop size distribution (RSD), has been a paramount consideration in advancing the radar rainfall estimation algorithms and microphysical parameterization 9-12. Owing to the significant contribution of TC RSDs in hydrometeorology and earth surfaces process, there has been increasing interest in exploring the RSD information of TCs from different oceanic regions 11,13-17. Conversely, most previous observations were conducted with RSD samples using a limited number of TCs or a portion of TC rainbands. Studies performed with numerical simulations and remote sensing data demonstrated the disparities in convection and precipitation distribution with radial distance from the TC center 18-24. In addition, despite the limited number of TCs measurements, recent studies have hinted at the inequalities in TC's RSD with radial distance 16,17. Nonetheless, up to now, an extensive framework that emphasizes the RSD features of TCs with their radial distance and intensity is yet to be known. Therefore, it is imperative to study the RSD of TCs in a long-term perspective to deduce their robust characteristics at different radial distances and category types. In this work, using long-term ground-based (disdrometer and radar) and re-analysis data sets, we elucidate the microphysical processes liable for the RSD changes with TCs radial distance and intensity. The results depict a decrease in rainfall rate and mass-weighted mean diameter with radial distance from the TC center, with a substantial decreasing pattern for intense TCs (CAT15) than the tropical storm category TCs. The microphysical attributions and rainfall retrieval relations disclosed for different intensities and radial distances can improve the TCs modeling simulations and radar precipitation estimation algorithms. The results present in this study provide conceivable microphysical attributes responsible for the RSDs variations at different radial distances and offer possible implications for the rain retrieval algorithms of ground-based and remote sensing radars.