Humid Regions Research Articles

Mathematical models for traffic-source PM2.5 dispersion in an urban street canyon considering the capture capability of roadside trees

Rapid urbanization increases the densely built-up blocks, the population and vehicles. Large amounts of particulate matter (PM), especially PM2.5 (PM with an aerodynamic diameter of 2.5μm or less), from vehicle exhaust are critical to human health. In typical street canyons in hot and humid regions, traffic-source PM usually diffuses to the densely built-up blocks through roadside trees. Roadside trees are a double-edged sword, serving as “guards” to absorb PM2.5 while may lead to PM2.5 gathering in street levels, thereby influencing the PM2.5 dispersion in the densely built-up blocks. To quantify the dispersion process, this study proposed traffic-source PM2.5 dynamic dispersion models considering the capture capability of roadside trees and built-up blocks based on the OSPM model. Due to the difficulty in obtaining the adsorption and deposition rate of the proposed models, the numerical simulations by ENVI-met software were used to solve and obtain the relationship between capture capability and characteristic index of roadside trees. Subsequently, The accuracy and effectiveness of the proposed traffic-source PM2.5 dynamic dispersion models were verified through field experimental data. Results show that the calculated PM2.5 concentration significantly linearly increased with the measured values with the determined coefficient (R2) of 0.98, and the first-order coefficient close to 1. It indicates that the proposed traffic-source PM2.5 dispersion model accurately quantified the impact of roadside trees on PM2.5 and its concentration dispersion process to the built-up blocks. This study provides suggestions for designing characteristic indexes of roadside trees and built-up blocks to improve the air quality of urban street canyons.

Revisiting the global distribution of the exponent of the power-function complementary relationship of terrestrial evaporation: Insights from an isenthalpic index

The complementary relationship (CR) of evaporation is one of widely-used approaches in estimating terrestrial evapration (E). However, the determination of the parameter values in CR-based models remains a difficult task. This is especially true for the new power-function complementary relationship (PCR) model developed recently, in which the key parameter that accounts for the effect of moisture advection over the drying land, b, must be well calibrated with consideration of an approporiate physical basis. Here, by proposing a new isenthalpic index that can be used for determining b directly without resorting to any a priori information of global E, this study found that the resulting b values (median = 1.64, standard deviation = 0.73) are generally smaller and display a narrower range than those reported recently by Kim et al. (2024). When applied with monthly input variables of 124 FLUXNET stations, the gridded b values improve upon E estimates that employ either i) a standard value of b (=2), or; ii) a calibrated value (same for all stations). The global distribution of the gridded b values –in contrast to those obtained by Kim et al. (2024) –aligns with its physical interpretation: low values (1 < b < 2) where the effect of moisture advection is weak (i.e., permanently/periodically wet, humid regions or regions far away from any significant external moisture source) and high ones (b > 2) when strong (i.e., warm arid/semi arid regions near a sea or high mountains of abundant moisture). The gridded b values improve the calibration-free PCR that employs a constant b (=2) and a Priestley-Taylor coefficient linked to the wet-environment air temperature.

Comprehensive analysis of HVAC control factors for elderly residents in hot and humid regions: A case study in Hong Kong

Occupant behavior significantly impacts energy consumption and indoor comfort through HVAC (Heating, Ventilation, and Air Conditioning) system operation. Existing behavioral models in building energy simulations mainly focus on environmental parameters, often overlooking physiological and social factors. This study introduces a multidimensional model that incorporates environmental perception, societal, economic, familial, physiological, and psychological factors. Data from 344 participants aged 60 and above were collected using questionnaires and indoor sensors during hot-weather months in 2021 and 2022. Logistic regression was employed to develop an HVAC usage model integrating physiological and environmental factors, revealing the explanatory power of diverse variables on HVAC operations. The results indicate that age, gender, income, housing size, family relationships, and sleep patterns have the highest explanatory capacity for air conditioner and fan usage. Non-physical factors are as significant as physical environmental factors for fan usage. The air conditioning model is most sensitive to income level. Low to moderate-income elderly individuals use air conditioning for much shorter durations compared to high-income counterparts, and aging reduces activation times, with a more pronounced effect in males. Additionally, hotter weather will amplify the gaps in expected air conditioning usage times due to income, age, and gender differences.

Increasing vulnerability of vegetation to Meteorological and Groundwater drought: A Case study in Argentina

Study RegionContinental Argentina, South America. Study FocusThis study integrates multiple data sources to analyze the response of vegetation to meteorological and groundwater drought events in Argentina. It utilizes GRACE satellite data to monitor water storage variations, the GLDAS hydrological model to track soil moisture levels, and NDVI to assess vegetation health, categorized by different vegetation types. Meteorological data facilitated the computation of drought severity using the Standardized Precipitation-Evapotranspiration Index (SPEI). Anomalies in groundwater storage, derived from these data, informed the calculation of the Grace Groundwater Drought Index (GGDI). A comprehensive statistical analysis was conducted to examine the impact of meteorological (SPEI) and groundwater (GGDI) droughts on various vegetation types. New Hydrological Insights for the RegionThe study reveals that from 2002 to 2022, GRACE-TWSA and GLDAS-TWSA displayed consistent trends in Argentina. Meteorological droughts, characterized by higher frequency and intensity, predominantly affect croplands and grasslands. Compared to lagged effects, the cumulative impact of droughts was found to be more significant. Shrublands demonstrated the greatest resistance to drought, whereas vegetation in humid regions showed lower drought tolerance. Notably, the duration associated with the lag effects of meteorological droughts decreased from 2.16 months in 2002–1.52 months in 2020, suggesting an increasing sensitivity of vegetation to these droughts. This underscores the urgency of developing targeted drought resilience and water resource management strategies.

Multifractal characterization of meteorological to agricultural drought propagation over India

Agricultural drought affects the regional food security and thus understanding how meteorological drought propagates to agricultural drought is crucial. This study examines the temporal scaling trends of meteorological and agricultural drought data over 34 Indian meteorological sub-divisions from 1981 to 2020. A maximum Pearson's correlation coefficient (MPCC) derived between multiscale Standardised Precipitation Index (SPI) and monthly Standardised Soil Moisture Index (SSMI) time series was used to assess the seasonal as well as annual drought propagation time (DPT). The multifractal characteristics of the SPI time series at a time scale chosen from propagation analysis as well as the SSMI-1 time series were further examined using Multifractal Detrended Fluctuation Analysis (MF-DFA). Results reveal longer average annual DPT in arid and semi-arid regions like Saurashtra and Kutch (~ 6 months), Madhya Maharashtra (~ 5 months), and Western Rajasthan (~ 6 months), whereas, humid regions like Arunachal Pradesh, Assam and Meghalaya, and Kerala exhibit shorter DPT (~ 2 months). The Hurst Index values greater/less than 0.5 indicates the existence of long/short-term persistence (LTP/STP) in the SPI and SSMI time series. The results of our study highlights the inherent connection among drought propagation time, multifractality, and regional climate variations, and offers insights to enhance drought prediction systems in India.

Increasing drought sensitivity of plant photosynthetic phenology and physiology

Understanding the impacts of drought on plant photosynthetic phenology and physiology is essential for accurately predicting annual gross primary productivity (GPP) and global carbon cycles. While droughts in different seasons can have different effects on plant growth and photosynthesis, a comprehensive understanding of how plant photosynthetic phenology and physiology respond to different seasons’ droughts and their temporal changes is lacking. Here, we comprehensively evaluated the drought sensitivities of plant photosynthetic phenology and physiology and their temporal trends in the past two decades, using the start/end of the photosynthetic seasons (SOS/EOS) and peak GPP (GPPmax) derived from FLUXNET ground observations since the 1990s and remote-sensing data (2001–2020) over the globe. Our results show that spring droughts leads to delayed SOS in arid ecosystems and advanced SOS in humid ecosystems. In contrast, droughts in summer and autumn generally advance EOS. In addition, spring droughts decrease GPPmax in arid regions but increase it in humid regions, whereas summer droughts lead to significant GPPmax reductions. More importantly, we observed significant increases in the drought sensitivity of SOS, EOS, and GPPmax over the last two decades, which is driven by long-term decreases in background soil moisture and increases in atmospheric water deficit under climate change. Furthermore, these increasing trends were projected to persist in the 21st century under Shared Socioeconomic Pathways 8.5 and 4.0. Overall, our findings underscore the critical role of drought timing in shaping ecosystem responses and highlight the growing vulnerability of ecosystem phenology and physiology to drought, which may restrict the increases in terrestrial carbon uptake under warming.

Soil Quality Assessment and Influencing Factors of Different Land Use Types in Red Bed Desertification Regions: A Case Study of Nanxiong, China

Soil environmental issues in the red bed region are increasingly conspicuous, underscoring the critical importance of assessing soil quality for the region’s sustainable development and ecosystem security. This study examines six distinct land use types of soils—agricultural land (AL), woodland (WL), shrubland (SL), grassland (GL), bare rock land (BRL), and red bed erosion land (REL)—in the Nanxiong Basin of northern Guangdong Province. This area typifies red bed desertification in South China. Principal component analysis (PCA) was employed to establish a minimum data set (MDS) for calculating the soil quality index (SQI), evaluating soil quality, analyzing influencing factors, and providing suggestions for ecological restoration in desertification areas. The study findings indicate that a minimal data set comprising soil organic matter (SOM), pH, available phosphorus (AP), exchangeable calcium (Ca2+), and available copper (A-Cu) is most suitable for evaluating soil quality in the red bed desertification areas of the humid region in South China. Additionally, we emphasize that exchangeable salt ions and available trace elements should be pivotal considerations in assessing soil quality within desertification areas. Regarding comprehensive soil quality indicators across various land use types, the red bed erosion soils exhibited the lowest quality, followed by those in bare rock areas and forest land. Within the minimal data set, Ca2+ and pH contributed the most to overall soil quality, underscoring the significance of parent rock mineral composition in the red bed desertification areas. Moreover, the combined effects of SOM, A-Cu, and AP on soil quality indicate that anthropogenic land management and use, including fertilization methods and vegetation types, are crucial factors influencing soil quality. Our research holds significant implications for the scientific assessment, application, and enhancement of soil quality in desertification areas.

Urbanization Effect on Regional Thermal Environment and Its Mechanisms in Arid Zone Cities: A Case Study of Urumqi

Urumqi is located in the arid region of northwestern China, known for being one of the most delicate ecological environments and an area susceptible to climate change. The urbanization of Urumqi has progressed rapidly, yet there is a lack of research on the urbanization effect (UE) in Urumqi in terms of the regional climate. This study investigates the UE of Urumqi (urban built-up area) on the regional thermal environment and its mechanisms for the first time, based on the WRF (Weather Research and Forecasting) model (combined with the Urban Canopy Model, UCM) simulation data of 10 consecutive years (2012–2021). The results show that the UE on surface temperature (Ts) and air temperature at 2 m (T2m) is strong (weak) during the night (daytime) in all seasons, and the UE on these is largest (smallest) in spring (winter). In addition, the maximum UE on both Ts and T2m is present over southern Urumqi in winter, whereas the maximum UE is identified over the northern Urumqi in other seasons. The maximum UE on Ts occurred in northwestern Urumqi at 18 LST (Local Standard Time, i.e., UTC+6) in autumn (reaching 5.2 °C), and the maximum UE on T2m occurred in northern Urumqi at 4 LST in summer (reaching 2.6 °C). Urbanization showed a weak cooling effect during daytime in summer and winter, reflecting the unique characteristics of the UE in arid regions, which are different from those in humid regions. The maximum cooling of Ts occurred in northern Urumqi at 11 LST in summer (reaching −0.4 °C), while that of T2m occurred at 10 LST in northern and northwestern Urumqi in winter (reaching −0.25 °C), and the cooling effect lasted for a longer period of time in summer than in winter. The UE of Urumqi causes the increase of Ts mainly through the influence of net short-wave radiation and geothermal flux and causes the increase of T2m through the influence of sensible heat flux and net long-wave radiation. The UE on the land surface energy balance in Urumqi can be used to explain the seasonal variation and spatial differences of the UEs on the regional thermal environment and the underlying mechanism.

Compound hot–dry events greatly prolong the recovery time of dryland ecosystems

ABSTRACT Compound hot–dry events cause more severe impacts on terrestrial ecosystems than dry events, while the differences in recovery time (ΔRT) between hot–dry and dry events and their contributing factors remain unclear. Both remote sensing observations and eddy covariance measurements reveal that hot–dry events prolong the recovery time compared with dry events, with greater prolongation of recovery time in drylands than in humid regions. Random forest regression modeling demonstrates that the difference in vapor pressure deficit between hot–dry and dry events, with an importance score of 35%, is the major factor contributing to ΔRT. The severity of stomatal restriction exceeds that of non-stomatal limitation, which restricts the vegetation productivity that is necessary for the recovery process. These results emphasize the negative effect of vapor pressure deficit on vegetation recovery during hot–dry events and project an extension of drought recovery time considering elevated vapor pressure deficit in a warming world.

Investigation of Cu Corrosion Defects Induced by Humidity Imbalance in the Cu Damascene Process of Semiconductors

As integrated circuit design rules shrink in semiconductor, Copper (Cu) has been employed as the back end of line (BEOL) interconnect metal to enhance device performance through reduced resistivity and resistive-capacitive delay.[1] However, Cu metal lines are prone to degradation caused by Cu oxidation-induced defects, including extrusions and voids, owing to their inherent properties.[2] Consequently, it becomes essential to regulate the oxidation rate during the chip fabrication process, particularly when the Cu metal line is exposed during the Damascene process. This control is crucial for ensuring long-term reliability and achieving a higher yield.[3]From the learning of earlier technological nodes, we are aware to and already precisely controlling both process queue time and wafer surface humidity. We must exercise control over the queue time, addressing both inter-process intervals and in-process queuing. [4] This underscores the importance of managing queue time and maintaining low environmental humidity to mitigate wafer surface defects when the FOUP (Front Opening Unified Pod) is opened at the EFEM (Equipment Front End Module).[5] Those humidity and queue times related Cu corrosion defects have been mitigated by N2 purge in FOUP and reducing the wafer quantity. However, dividing the lot, typically consisting of 25 wafers, by half or less to reduce queue times leads to an imbalance in low humidity due to N2 purging. This occurs when the FOUP is opened in EFEM.This paper examines Cu corrosion under low humidity conditions in a FOUP with a small quantity of wafers, specifically examining the influence of queue time during N2 purging in the EFEM. Through simulation of the interaction between the inlet air entering the EFEM and the purged N2 gas, a vulnerable area is identified where copper oxidation takes place. In addition, we propose an arrangement to mitigate high humidity, supported by experiments conducted under real equipment conditions.Fig. 1 shows Cu corrosion defects after ILD etching at around 20% RH in the FOUP. This defect is only observed in the lower slot of the FOUP on the N2 purged load port. Figure 2 illustrates a chart depicting the humidity inside the FOUP under various conditions. The humid region within the FOUP when opened on the N2 purged load port without wafers. (Fig.2a) While the extent of the humid area is contingent upon the flow rate of the N2 purge and the intake of air through the Fan Filter Unit (FFU), the vortex of the inlet air from the cleanroom (<42% RH) is notably observed at the bottom and front side of the FOUP. Therefore, wafers stored in the lower slot of the FOUP face an increased risk of Cu corrosions when subjected to elevated humidity levels during processes like ILD etching and subsequent cleaning. Specifically, an extended queue time amplifies the probability of Cu defects occurring in this high-humidity slot compared to slots with lower humidity. We observed an unintended increase to 28.2% RH in specific configurations when reducing the quantity of wafers to minimize queue time. (Fig. 2b)Hence, we propose an arrangement for wafers that maintains low humidity with small quantity. When placing 12 wafers in the FOUP, an arrangement with equal spacing from the first slot to the 25th slot ensures uniform N2 flow, thereby reducing the highest humidity from 28.2% RH to 14.0% RH by half. (Fig.3a) Alternatively, positioning all wafers on the upper section is another method. (Fig.3b) Therefore, by halving the quantity of wafers and reducing the process wait time by half, and applying the optimal wafer arrangement that maintains low humidity balance even with a small number of wafers, we confirmed the absence of Cu corrosion.

Natural Capping Enhancing the Resilience of Earthen Heritage Under Rainfall Impacts

ABSTRACT Soft capping has proven effective in enhancing masonry ruins in humid regions. To-date, there are limited studies on the use of soft capping for earthen heritage in arid and semi-arid regions. Considering the diverse climatic conditions and the presence of vegetation on the Northern China earthen sites, there is an urgent need to study the effect of these vegetations on earthen heritage sites. As the plant species used in the previous studies are mainly based on artificial selection, we propose to use native plant species that are typically found in the study site and define the application of native plant species as ‘natural capping’. Taking the Ming dynasty Shanxi Great Wall sections as case study, four scale-down rammed earth test walls were subjected to rainfall tests under four patterns of rainfall once. Results showed that native plants excel in Northern climates. Under moderate rainfall, the moisture at the wall head of natural capping walls is nearly constant. However, when subjected to heavy and extreme rainfall, natural capping walls reduced inner wall moisture infiltration by 5.56%–7.52% and material loss by 58.24%–75.04%. Post-rainfall monitoring demonstrated that natural capping has sustainable benefits for temperature and moisture reduction in summer.

Diversity and seasonality of horse flies (Diptera: Tabanidae) in Amazon Forest fragments of Monte Negro, Rondônia, Western Amazon.

Tabanidae are considered a nuisance to humans, wild animals, and livestock due to their painful, annoying, and insistent biting. Tabanids transmit some pathogens and parasites biologically and mechanically. In humans, there are relatively few pathogens transmitted regularly. Still, tabanids serve as vectors of a number of disease agents of animals, including viruses, bacteria, protozoans, and nematodes. They are more abundant in tropical and humid regions, and their seasonal patterns are affected by habitat changes such as deforestation and fragmentation. Here, we analyze the tabanid fauna in Monte Negro, a central municipality of Rondônia, Brazil, comparing abundance, richness, and diversity in forest and pasture habitats. Traps were set for 5days a month for 12 consecutive months. We also examined how abiotic factors (humidity, temperature, and rainfall) affected the abundance, diversity, and richness and the effectiveness of Malaise and Nzi traps as sample methods. The influence of climatic variables on the richness and abundance of the species was tested using generalized linear models, and we used non-parametric dimensional scaling (nMDS) for analysis of species composition and diversity in different traps and environments. We collect 1032 specimens of 25 species. The most abundant species were Tabanus antarcticus, Dichelacera tetradelta, Tabanus mucronatus, and Leucotabanus albovarius. Forest habitats had the highest number of tabanids, followed by pasture and the anthropized area, and there was no significant difference regarding the effectiveness of the Malaise and Nzi traps. The study provides new information on the distribution and ecology of tabanids in Brazil.

Kinetic and cracking analysis of paddy rice drying using refrigeration-assisted air dehumidification system

The presence of high relative air humidity in regions characterized by a humid climate results in a slow drying process and the rehydration of paddy. To address this issue, the utilization of a liquefied petroleum gas refrigeration system for the purpose of dehumidifying the ambient air has been shown to reduce drying time and enhance the quality of the final product. In the present investigation, the impact of ambient air dehumidification on the quality and moisture reduction of the Hashemi rice variety was examined. The drying of paddy was modeled and optimized using the Response Surface Method, taking into consideration three key factors: temperature (40, 45, and 50 °C), air velocity (1.7, 2.2, and 2.7 m/s), and relative air humidity (70, 80, and 90 %) as the variables in the conducted experiments. The findings of this study revealed that under dehumidification conditions, samples with a moisture content of 6 % exhibited the lowest cracking rate of 2 %. Moreover, the use of liquefied petroleum gas resulted in a 13 % reduction in cracking and drying times, ranging from 22.3 % to 68.9 %, depending on the experimental conditions. Irrespective of whether dehumidification was employed or not, the temperature was identified as the most influential parameter, impacting the experimental responses by 73.29 % and 73.09 % for the non-dehumidified and dehumidified conditions, respectively. Under optimal conditions, a cracking rate of 2 % was attained during dehumidification at a temperature of 40 °C, a relative air humidity of 80 %, and an air velocity of 1.7 m/s, yielding a desirability index of 0.958. The Response Surface Method, when applied in the dehumidification case, displayed an excellent fit between the experimental and predicted data for both the moisture content (R2 = 0.99) and the cracking index (R2 = 0.98). These results demonstrate the efficacy of the refrigeration system that employs liquefied petroleum gas inefficiently drying paddy in humid regions, rendering it applicable in industrial settings.

The adaptability of Garut sheep grazing on oil palm and rubber plantations in tropical conditions of Indonesia.

The productivity of sheep in humid tropical plantation areas relies on their ability to adapt. Oil palm plantations serve as potential grazing lands for livestock. This study aimed to identify Garut sheep adaptations in oil palm and rubber plantations of the Garut district, West Java, Indonesia. The total number of sheep used was 103 as the object of this study. Each individual of sheep was used for several different observations, including: Physiological assessment using 24 sheep of various ages, molecular analysis of heat stress using 31 sheep, worm egg count using 59 sheep, and for morphological assessment using 98 sheep. A general linear model was employed to analyze rectal temperature (RT), heart rate (HR), respiratory rate, number of eggs in each gram of sample feces, body weight (BW), body condition score, and morphometric measurements according to age and sex. Forage was compared between oil palm and rubber plantations during the vegetation analysis. RT, HR, and panting frequency were significantly (p < 0.05) affected by the age and sex of the sheep. The mutation was found in the coding region of the HSP70 gene, which is approximately 232 bp long. Fecal eggs were found in 99% of the fecal samples, consisting of 100% Strongyle eggs and 1.75% Moniezia eggs. BW, body condition score, shoulder height, body length, pelvic height, chest circumference, and number of eggs were significantly affected (p < 0.05) by the age and sex of the sheep. The average fresh matter of vegetation under the plantation was 248.69 ± 120.94 g/m2 and 718.15 ± 249.93 g/m2 for oil palm and rubber plantations, respectively. Garut sheep were adapted to oil palm and rubber plantations in the humid tropical region. Plantations are potential sources of sheep grazing and roughage. Further research is needed regarding the consumption of forages in oil palm and rubber plantations.

Recycling Selected Wetlands’ Sediments for a Vegetable Crop Cultivation in Terrestrial Ecosystem of a Humid Region

This study aimed to evaluate the selected wetlands' sediments regarding physicochemical attributes including heavy metals (HMs), and their potentiality to be used in crop cultivation with or without mixing with different generic farmers' field soils in the upland. Forty geo-referenced sediment samples were collected from each study site (n=3), and mixed to get three separate composite samples for mineral nutrients, HMs analyses and experimentation. Two pot experiments were conducted following Completely Randomized Design (CRD) with three replicates using farmers’ field soils (FFS) Gleysols and Cambisols to grow amaranth. The treatments were: T0: FFS; T1: FFS + wetland sediment of hilly area I (1:1); T2: FFS + wetland sediment of hilly area II (1:1); T3: FFS + wetland sediment of a floodplain area (1:1); T4: wetland sediment of hilly area I; T5: wetland sediment of hilly area II; T6: wetland sediment of a floodplain area. Regarding nutrient elements, exchangeable K, extractable P, Ca, and Zn were observed higher in wetland sediment of hilly area II except organic carbon (OC). Only Cd, Pb, and Ni were individually found higher than the maximum permissible addition for all wetland sediments, but all HMs collectively posed no “ecological risk”. The highest values of the plant growth index of amaranth were observed for T5 treatment. Moreover, the highest total fresh and dry biomasses were found in T5 treatment. The highest nutrient uptake was observed in T5 treatment for the most of nutrients. Studied wetlands’ soil materials, OC, and nutrients could be used to benefit upland crop cultivation.

Hydrochemical and isotopic characteristics on the southern and northern slopes of the Himalayas: spatio-temporal controls and source apportionment

Water-soluble ions, inorganic nitrogen, and stable isotopes in precipitation were assessed from the southern (Koshi Tappu and Khandbari) and northern slopes (Lhasa and SET) of the Himalayas to understand the sources, chemistry of regional precipitation, and climatic processes. Water soluble ions showed distinct seasonal variation, with higher concentrations in the non-monsoon. The concentration of ionic species was highest in Koshi Tappu, followed by Lhasa, SET, and Khandbari. The sources were from the terrigenous (Ca2+, HCO3−), marine (Na+ and Cl−), anthropogenic (SO42−, NO3−, and NH4+), terrigenous and marine (Mg2+), and biomass-burning (K+). The southern slope, relative to the northern, was more prone to anthropogenic emissions with higher deposition. Among all sites, inorganic nitrogen deposition at Koshi Tappu was higher than the threshold value (10 kg ha−1 y−1). The isotopic composition during the study period was higher in non-monsoon, started declining from June, and depleted in July and August compared to other months, i.e., the monsoon mature phase, along the south-to-north transect. The diminished value of stable isotopes in precipitation with increasing altitude underlines the evidence of the orographic effect in isotopic composition. Our study delineated that the higher/lower d-excess value increased with altitude on the southern/northern slope of the Himalayas. The backward trajectory analysis and the National Centers for Environmental Prediction's Final (NCEP FNL) datasets identified that most of the trajectories arrived from warm and humid low-latitude regions during monsoon and westerlies in non-monsoon. Thus, the chemical characteristics and stable isotopic composition of precipitation differed on the southern and northern slopes of the Himalayas by orographic effect and various sources. This study provides new insights into the atmospheric environment and climatic control of stable isotopes in the Himalayan Tibetan Plateau and facilitates monitoring of transboundary air pollution.

Assessing the winter indoor environment with different comfort metrics in self-built houses of hot-humid areas: Does undercooling matter for the elderly?

Thermal comfort in housing is vital for well-being. Despite hot and humid regions experiencing shorter cold periods compared to heatwaves, vulnerable populations are susceptible to threats from cold snaps. However, existing research overlooks undercooling risks in hot regions during winter. This study examines self-built houses in densely populated, hot and humid areas, mainly occupied by elderly residents. We conducted an on-site measurement recording hourly indoor air temperature, humidity, and black globe temperature during wintertime. Two thermal comfort metrics (aPMV and adaptive regression model) and two resilience metrics (SET degree-hour, Hours of Safety) were used to quantify thermal conditions during cold periods under current and future climate conditions. The results show that undercooling hours in recent years exceed 90 % of wintertime using aPMV index and adaptive regression models. Under future climate scenarios (Representative Concentration Pathways), undercooling hours only decrease by 10 %–25 % from 2020 to 2100 across all metrics. Extreme cold events in 2018 saw SET degree-hours double the thermal resilience threshold, while they pose health risks to the elderly for up to 21 days according to the HOS metrics. This study aims to identify the importance of addressing winter thermal comfort in hot and humid regions and to assess the risk posed by cold snaps to vulnerable populations. By quantifying these risks, the study contributes to better decision-making regarding hot-humid region housing thermal retrofit strategies for architects, engineers, and other stakeholders.

Spatiotemporal patterns in persistent precipitation extremes of the Chinese mainland (1961–2022) and association with the dynamic factors

Previous studies on extreme precipitation events have primarily focused on the intensity of such events during fixed periods, without considering the entirety of extreme precipitation events and conducting a comprehensive examination of the intensity and frequency of more disastrous persistent extreme precipitation (PEP) events. In this paper, persistent extreme precipitation indices (PEPIs) related to intensity, frequency, duration, and contribution rates were constructed, utilizing a gridded daily precipitation dataset and atmospheric circulation indices data from China for the period 1961–2022 to analyze the spatial distribution, spatiotemporal trends, and seasonal patterns and variations of PEPIs across different regions of China and the potential impact of the dynamic factors on the spatiotemporal variations of PEPIs. The results are crucial for effectively predicting future changes and informing planning for adaptation strategies: From 1961 to 2022, (1) China's PEP pattern displays distinct regional variations. PEP has been prevalent in Western Arid (Semi-Arid) Zone (WAS) and Qinghai-Tibet Plateau (QT) regions, with higher occurrence frequency, duration, and contribution rates to total extreme precipitation (44.91% and 42.01%) and overall precipitation (26.35% and 29.08%). Conversely, the humid eastern regions exhibit greater event intensity. (2) Intensity-related PEPIs show a significant increase, while the frequency and contribution rate-related PEPIs tend to decrease, indicating less frequent but more concentrated PEP events. (3) Seasonal distribution of PEP events shows a primary concentration in QT, North China (N), the Eastern arid zone (EA), and Northeast China (NE) from June to September and they occur more frequently during spring and summer in Central (C) and South China (S) regions. Summer variations predominantly account for annual PEP variability and trends. (4) WPSHII, SCSSHII, WPWPSII, APVII, NHPVII, NINO3 predominantly affect the WAS, QT, NE, C, and S regions, with WPSHII having the broadest impact, notably on the QT, C, S, and NE regions. In the WAS region during autumn, the interaction of NAO and WPSHII explains 72% of the intensity of PEP events.

Effects of Design Factors and Multi-Stage Environmental Factors on Hydrological Performance of Subtropical Green Roofs

Environmental and design factors determine the stormwater management capacity of green roofs; however, the design and environmental factors that impact their hydrological performance in subtropical humid regions are poorly understood. In particular, meteorological factors have received little attention. Meteorological factors vary greatly at different stages of a rainfall event (e.g., during the rainfall and outflow). Therefore, the impact of meteorological factors at different stages on hydrological performance should be considered separately to obtain a more accurate picture of their effects on hydrological performance. In this study, experimental green roofs were established based on four substrate types and two depths. For the first time, this study systematically explored the effects of design factors for the substrate (type and depth) and multi-stage environmental factors on the hydrological performance of green roofs. Environmental factors, including meteorological factors, from three critical stages (before and during a rainfall event and during the outflow), and rainfall characteristics (e.g., rainfall depth and rainfall duration) were incorporated to determine the variation in hydrological performance. The effects of multi-stage environmental factors on retention and peak reduction were analyzed, with a ranking of each factor’s relative importance. Environmental factors played a leading role in determining hydrological performance. However, the impact of multi-stage environmental factors was not as important as that of rainfall depth and antecedent volumetric water content. Differences in hydrological performance were compared across combinations of design factors. No significant differences were observed across substrate types and depths. However, potential interactive effects might exist, though these were not significant compared to environmental factors (e.g., rainfall depth and rainfall duration). These results confirmed that the meteorological factors in the different event-related stages significantly impacted the hydrological performance. Quantifying the effects of design and environmental factors is critical for hydrological performance evaluation. The results provided a broader perspective on understanding influence mechanisms of hydrological performance and highlighted the impact of microclimates on hydrological performance.

A unified runoff generation scheme for applicability across different hydrometeorological zones

Runoff generation in humid and semi-arid regions are usually dominated by saturation-excess mechanism and infiltration-excess mechanism, respectively. However, both mechanisms can co-exist in semi-humid regions. Therefore, we proposed a unified runoff generation scheme to represent the single and mixed runoff generation processes, making it applicable for different hydrometeorological conditions. The saturation-excess runoff generation scheme of the Xin'anjiang model was integrated with a modified Horton infiltration scheme at the grid cell scale. By substituting the original runoff generation scheme of the grid-Xin'anjiang (GXAJ) with the integrated scheme, we developed a new distributed hydrological model called grid-Xin'anjiang-infiltration-excess (GXAJ-IE) model. GXAJ-IE was tested in four watersheds and compared with two benchmark models with single runoff generation mechanism. The results indicate that GXAJ-IE model has higher flexibility and robustness in reproducing flood hydrographs under different rainfall conditions in semi-humid watersheds and has comparable performances with the benchmark models in humid and semi-arid regions.