Yi-Shin Jang

Montane cloud forests (MCFs), ecosystems critically dependent on persistent cloud immersion and high moisture availability, have been presumed vulnerable to regional warming and atmospheric drying. Yet their microclimatic resilience under regional climate variability remains poorly understood. Here we show that MCFs maintain remarkably stable near-surface relative humidity (RH), despite sustained regional warming, using a 42-year (1980–2021) high-resolution (2-km, hourly) climate dataset from Taiwan. These forests also exhibit substantially lower interannual RH variability than adjacent non-cloud-forested regions. This persistence arises from an interplay of mechanisms, including local and nonlocal water vapor supply under variable rainfall regimes, cloud-mediated temperature moderation, and nonlinear thermodynamic regulation. Together, these processes buffer MCFs against atmospheric drying. Our results complement prevailing assessments of MCF vulnerability to changing climate, by revealing their retention of a stable microclimate amid regional climate fluctuations. This study advances understanding of how mountain ecosystems regulate their microclimate and provides a mechanistic framework for evaluating microclimate persistence in cloud forests worldwide.

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.

Vapor pressure deficit (VPD), a key indicator of atmospheric dryness, is strongly influenced by diurnal cycles of temperature ( T ) and relative humidity (RH). While these cycles are typically inversely locked in-phase, recent research has identified diurnal hysteresis, characterized by a time lag between T and RH; yet, its impact on VPD under changing climates remains poorly understood. In this study, we examine how diurnal T /RH hysteresis modulates VPD across different climates using observational data alongside high-resolution reanalysis and simulations. Here, we find that regions exhibiting strong diurnal T /RH hysteresis, especially in some waterside and montane regions, experience earlier daily VPD peaks. We also demonstrate that global warming weakens diurnal T /RH hysteresis, leading to amplified VPD increasing trends and greater ecosystem stress. These results highlight the need for improved representation of diurnal T /RH interactions in climate models to better predict atmospheric dryness and its impacts on land-atmosphere feedbacks, ecosystems, and regional water cycles.

Forests moderate the microclimate through evapotranspiration and biomass heat flux. However, understanding the contributions of dense forests remains challenging due to observational limitations. Our in-situ observations show that forests regulate the diurnal temperature range by approximately 2 °C compared to open fields. The Community Terrestrial System Model simulation reveal that latent heat and sensible heat fluxes are overestimated by around 10% during the daytime. The nighttime temperatures are underestimated when biomass heat storage (BHS) is excluded. Furthermore, the Single-Column Atmospheric Model indicates that the misestimated daytime heat flux leads to the slight overestimation of boundary layer height. Notably, BHS decreases daytime temperature by adjusting sensible heat flux through land–atmosphere interaction. The warming bias resulting from neglecting BHS reduces vegetation transpiration, further leading to an underestimation of daytime latent heat flux. Facing the threats of climate warming and deforestation, understanding BHS characteristics in models is pivotal for accurately representing land–atmosphere interactions.

Low‐clouds and fog moderate the diurnal temperature range (DTR) through radiative effects. Consequently, frequent foggy events make montane cloud forests (MCFs) stable and unique. However, high‐resolution observations in the forest understory are rare. To investigate the DTR variation in elevations, we surveyed the Central Cross‐Island Highway in central Taiwan along the altitude of 0–3,000 m across both the non‐cloud forest and MCFs. The results from paired weather stations revealed that the DTR increases significantly with altitude in open fields but not in the forest's understory. Furthermore, the continuous observations in altitude indicate that smaller DTRs were found in both open field and understory sites in the MCF compared with those in low‐ and high‐altitude sites. The DTR discontinuity highlights the indispensability of MCF for the mountain ecosystem. Further simulating the integrative effect of the climate and land‐use change on fog is crucial for the ecoclimate in mountainous regions.

Low-clouds and fog moderate the diurnal temperature range (DTR) through radiative effects. Consequently, frequent foggy events make montane cloud forests (MCFs) stable and unique. However, observat...

Low-clouds and fog moderate the diurnal temperature range (DTR) through radiative effects. Consequently, frequent foggy events make montane cloud forests (MCFs) stable and unique. However, observations in the understory of the forest are rare. To investigate the DTR variation in elevations, we surveyed the Central Cross-Island Highway in central Taiwan transects with MCFs. The results from paired weather stations revealed that the DTR increases significantly with altitude in open fields but not in the forest’s understory. Furthermore, the continuous observations in altitude across non-cloud forest and MCFs indicate that DTR decreases in both the open field and understory of MCFs. The DTR discontinuity highlights the indispensability of MCF for the mountain ecosystem. Further simulating the integrative effect of the climate and land-use change on fog is crucial for the ecoclimate in mountainous regions.