Chao‐Tzuen Cheng

Cloud‐fog formation substantially reduces near‐surface solar radiation and modulates land‐atmosphere interactions, but quantifying such reduction is limited by sparse mountain observations. Using a 1‐km geostationary satellite‐retrieved product, we apply the Reduction Ratio of Solar Radiation (RR _SR ), an empirical normalized metric that quantifies near‐surface solar radiation deficits relative to a local maximum solar radiation baseline. Applying RR _SR over Taiwan reveals a strong seasonal contrast. Summer RR _SR exhibits a distinct land‐type gradient (montane cloud forests > other forests > non‐forests), peaking within the mid‐elevations (500–2,500 m a.s.l.). In winter, prevailing northeasterly flow overrides local land‐type influences. Strong northeasterly events enhance RR _SR > 1.5‐fold in windward lowlands (SR provides a practical diagnostic for ecohydrology and surface energy budgets, although its uncertainties are larger under cloudy or foggy conditions in complex terrain.

Fog is a vital component of montane climates, providing essential moisture for cloud forests and supporting the productivity of high‐value crops. This life‐sustaining feature, however, is increasingly vulnerable to disruption from rapid urbanization and climate change. To investigate the individual and combined impacts of these two drivers on fog dynamics, we employed a high‐resolution weather model and a full factorial design, excluding the effect of aerosols. Our results reveal that urbanization shifts the fog belt upward, reducing fog occurrence in lowlands while enhancing it at mid‐elevations. In contrast, warming‐induced circulation changes reduce fog in the west of the Central Mountain Range (CMR) but promote fog formation in the east. The complex interplay among local terrain, urbanization, and climate warming resulted in asymmetric changes in mountain fog, which can worsen the water stress differential between the western and eastern flanks of the CMR in Taiwan.

Convective afternoon rainfall (CAR) is a significant summer rainfall feature in Taiwan. This study investigates the projected uncertainties in summer CAR in Taiwan, using a dynamical downscaling approach with the Weather Research and Forecasting Model (WRF) and the High-Resolution Atmospheric Model (HiRAM). The projections were driven by four different sea surface temperature (SST) categories derived from CMIP5 model simulations under the RCP8.5 scenario. All projections indicate a reduced frequency but increased intensity of CAR over Taiwan by the end of the 21st century. However, notable differences in the degree of CAR changes were observed among simulations with varying degrees of Pacific SST warming. These variations in potential future changes in CAR frequency and intensity can be attributed to the variations in daytime thermal instability, local inland wind convergence, and moisture flux convergence over Taiwan. Furthermore, this study explored the linkage between local thermodynamic conditions and projected large-scale circulation patterns.

This study seeks to understand the impact on the forest biomass of different kinds of environmental disturbance, including high winds from typhoons, land‐use/land‐cover changes (LULCC), and CO₂ fertilization. A series of factorial experiments addressing the impact of different types of environmental disturbance on the forest biomass in Taiwan was conducted using the advanced ORCHIDEE‐CAN land surface model with a recently developed wind‐throw module. The climatic forcing driving the ORCHIDEE‐CAN land surface model was first simulated by an atmospheric general circulation model, then dynamically downscaled to a more satisfactory spatial and temporal resolution. The initial and boundary conditions applied in the numerical simulations were based on the long‐term CO₂ concentration and LULCC reconstruction, respectively. The model simulation showed an increase in the aboveground wood volume from 209 m³ ha⁻¹ in 1979 to 229 m³ ha⁻¹ in 2017, and the dynamics were consistent with those recorded in the national forest inventory. The annual average carbon sequestration rate over the past 39 years was 0.5 m³ ha⁻¹ yr⁻¹ for a forested area of 2.4 M ha. The most surprising finding was the contribution of the wind disturbance to wood loss, which was at almost the same level as the annual carbon sequestration rate. The LULCC experiment showed a trade‐off between afforestation and deforestation in forest biomass accumulation in Taiwan from 1979 to 2017. The CO₂ fertilization effect contributed to an enhancement of forest biomass stock of around 39%, while the CO₂ concentration increased from 296 to 406 ppm over 39 years.

Summer rainfall in Taiwan is composed of four types of rain events: tropical cyclone (TC), frontal convection (FC), diurnal convection (DC), and other southerly convection (SC) that propagates from the nearby ocean. In this study, we accessed the present‐day simulation (1979–2003) and future projection (2075–2099, the Representative Concentration Pathway 8.5 scenario) of rainfall in Taiwan by using the regional Weather Research and Forecasting model driven by the global High Resolution Atmospheric Model. The results indicated that the dynamical downscaling process adds value to the present‐day simulation of summer rainfall in Taiwan and the contribution of different types of rain events. It was found that summer rainfall in Taiwan will increase in a warmer future and that this change was mainly due to an increase in SC rainfall (i.e., light rainfall event). The following trends in Taiwan rainfall were also predicted in a warmer future: (1) SC rainy days will increase because the intensified monsoonal flow facilitates the propagation of more SC toward Taiwan, (2) TC rainy days will decrease as the Western North Pacific subtropical high extends southwestward and prevents TC systems from passing over Taiwan, (3) DC rainy days will decrease in response to the increased local thermal stability, and (4) FC rainy days will show no significant changes. Moreover, all types of rainfall are projected to become more intense in the future due to the increased moisture supply in a warmer climate. These findings highlight how the rainfall characteristics in East Asia may change in response to climate change.