Regional discrepancies in the microphysical attributes of summer season rainfall over Taiwan using GPM DPR.

Taiwan, an island located in the northwest Pacific region, is influenced by heavy rainfall events during warm seasons, particularly from June to August. Interaction of precipitating clouds with the complex topography results in inhomogeneous and intense rainfall over Taiwan. Hence, the present study investigates the regional discrepancies in the microphysical characteristics of summer season rainfall over (north, south, east, and central) Taiwan using 9 years (2014-2022) of GPM DPR measurements. The results showed clear distinctions in the precipitation and raindrop size distributions over the north, south, east, and central Taiwan. The contoured frequency by altitude diagrams (CFADs) of radar reflectivity, rainfall rate, drop diameter, and concentration clearly infer the dominance of large-size super cooled liquid and ice particles above the melting layer and rain particles below the melting layers in the south and central Taiwan. Central (north) Taiwan is dominated by large-size (small) drops among four regions. Higher concentrations of large drops over central Taiwan (principally from convective precipitation) and south Taiwan (primarily from stratiform precipitation) is attributed to higher rainfall amounts over these two regions than the north and east Taiwan. Furthermore, irrespective of precipitation type and geographic region, summer monsoon rainfall over Taiwan is dominated by coalescence and breakup processes. The microphysical characteristics of summer season rainfall addressed in this study could assist in refining the cloud modeling simulations over complex topography in Taiwan.

An insight into the microphysical attributes of northwest Pacific tropical cyclones.

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.

An assessment of tropical cyclones rainfall erosivity for Taiwan.

Rainfall erosivity (or water erosion) has severe implications on agriculture, water, and land use management. Though, there were Rainfall erosivity studies on regional and global scale, tropical cyclones' Rainfall erosivity is poorly assessed and have not been documented for one of the most cyclones affecting regions of the world like Taiwan. Here, using 15-years of raindrop size distributions (RSD) and 60-years of hourly rain gauges data, we estimated cyclones (also called typhoons) rainfall erosivity over Taiwan, and establish that typhoons' mean rainfall erosivity is higher than the global mean rainfall erosivity. Moreover, regional variability of typhoons rainfall erosivity showed an increasing pattern from north to south (Taipei to Pingtung), with relatively higher values over eastern and southern parts of Taiwan. The annual mean erosivity of typhoons rainfall showed raising trends over eastern and southern Taiwan during 1958-2017. Our results provide an insight in assessing the land use and agricultural management for Taiwan.

The relationship between typhoons' peripheral circulation and ground-level ozone concentrations in central Taiwan.

Surface data of meteorological parameters (wind speed, wind direction, and mixing height) and air pollutant concentrations (O3, NO, and NO2) were collected for a 92-day period associated with typhoon formation in 2005. The influence of typhoons on O3 concentration were defined by azimuth and distance from Taiwan, and Types A, B, and C correspond to typhoons less than 1,500 km from Taiwan and located between azimuths 45° and 135°, 135° and 225°, and 225° and 45°, respectively. Type D corresponds to typhoons more than 1,500 km from Taiwan. Titration reactions were conducted at three temporal phases: 2000-0700, 0800-1100, and 1200-1400 LST (Local Standard Time). The air pollution model (TAPM) was used to simulate wind fields and trajectories of air masses. It was determined that typhoon position affected O3 concentration, temporal and spatial patterns of O3 titration and vertical meteorological characteristics, which were not all at the statistically significant level.

Relationships between cold-temperature indices and all causes and cardiopulmonary morbidity and mortality in a subtropical island.

This study aimed to identify optimal cold-temperature indices that are associated with the elevated risks of mortality from, and outpatient visits for all causes and cardiopulmonary diseases during the cold seasons (November to April) from 2000 to 2008 in Northern, Central and Southern Taiwan. Eight cold-temperature indices, average, maximum, and minimum temperatures, and the temperature humidity index, wind chill index, apparent temperature, effective temperature (ET), and net effective temperature and their standardized Z scores were applied to distributed lag non-linear models. Index-specific cumulative 26-day (lag 0-25) mortality risk, cumulative 8-day (lag 0-7) outpatient visit risk, and their 95% confidence intervals were estimated at 1 and 2 standardized deviations below the median temperature, comparing with the Z score of the lowest risks for mortality and outpatient visits. The average temperature was adequate to evaluate the mortality risk from all causes and circulatory diseases. Excess all-cause mortality increased for 17-24% when average temperature was at Z=-1, and for 27-41% at Z=-2 among study areas. The cold-temperature indices were inconsistent in estimating risk of outpatient visits. Average temperature and THI were appropriate indices for measuring risk for all-cause outpatient visits. Relative risk of all-cause outpatient visits increased slightly by 2-7% when average temperature was at Z=-1, but no significant risk at Z=-2. Minimum temperature estimated the strongest risk associated with outpatient visits of respiratory diseases. In conclusion, the relationships between cold temperatures and health varied among study areas, types of health event, and the cold-temperature indices applied. Mortality from all causes and circulatory diseases and outpatient visits of respiratory diseases has a strong association with cold temperatures in the subtropical island, Taiwan.