Category: New Publications Page 1 of 4

Our new paper, “Compound heat and ozone pollution in the urban environment“, is published in Urban Climate (IF: 6.9).

The paper can be downloaded at https://doi.org/10.1016/j.uclim.2025.102511.

Authors: Chenghao Wang, Xiao-Ming Hu, Sarah Feron, Jessica Leffel, & Raúl R. Cordero

Abstract: Ground-level ozone pollution and extreme heat are closely linked environmental stressors that often peak during similar warm-season conditions. Their co-occurrence as compound events can significantly amplify negative health impacts, particularly in densely populated urban areas. In this study, we systematically characterized the frequency, duration, and cumulative intensity of warm-season compound heat and ozone pollution events across all urban areas and their rural surroundings in the contiguous U.S. (CONUS), using long-term, high-resolution daily air temperature and pollution datasets. We found that urban heat waves, defined using daily maximum air temperature, were generally more frequent, more intense, and longer lasting than their rural counterparts, primarily due to the daytime urban heat island effect. In contrast, over half of the U.S. cities experienced fewer, less intense, and shorter ozone pollution episodes than nearby rural areas, largely reflecting differences in ozone chemical regimes. Despite these contrasting patterns, compound heat and ozone pollution events were more frequent in 88.8 % of urban areas, with higher cumulative heat and ozone pollution intensities in 91.1 % and 88.1 % of cities, respectively. However, compound event durations tended to be shorter in urban environments. These findings highlight the dependence of such compound events on local factors such as precursor emissions, as well as background conditions such as regional meteorological patterns, emphasizing the need for tailored mitigation strategies to simultaneously reduce heat stress and ozone pollution. This study also lays the foundation for detailed regional numerical simulations to elucidate the mechanisms that drive urban–rural disparities during these compound events.

DOI: https://doi.org/10.1016/j.uclim.2025.102511

Our new paper, “Ultrafine-resolution urban climate modeling: Resolving processes across scales“, is published in Journal of Advances in Modeling Earth Systems (IF: 4.6).

The paper can be downloaded at https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2025MS005053.

Authors: Chenghao Wang, Yongling Zhao, Qi Li, Zhi-Hua Wang, & Jiwen Fan

Abstract: Recent advances in urban climate modeling resolution have improved the representation of complex urban environments, with large-eddy simulation (LES) as a key approach, capturing not only building effects but also urban vegetation and other critical urban processes. Coupling these ultrafine-resolution (hectometric and finer) approaches with larger-scale regional and global models provides a promising pathway for cross-scale urban climate simulations. However, several challenges remain, including the high computational cost that limits most urban LES applications to short-term, small-domain simulations, uncertainties in physical parameterizations, and gaps in representing additional urban processes. Addressing these limitations requires advances in computational techniques, numerical schemes, and the integration of diverse observational data. Machine learning presents new opportunities by emulating certain computationally expensive processes, enhancing data assimilation, and improving model accessibility for decision-making. Future ultrafine-resolution urban climate modeling should be more end-user oriented, ensuring that model advancements translate into effective strategies for heat mitigation, disaster risk reduction, and sustainable urban planning.

DOI: https://doi.org/10.1029/2025MS005053

Our new paper, “Enhancing climate-driven urban tree cooling with targeted nonclimatic interventions“, is published in Environmental Science & Technology (IF: 10.9).

The paper can be downloaded at https://pubs.acs.org/doi/10.1021/acs.est.4c14275.

Authors: Zhaowu Yu, Siheng Li, Wenjun Yang, Jiquan Chen, Mohammad A. Rahman, Chenghao Wang, Wenjuan Ma, Xihan Yao, Junqi Xiong, Chi Xu, Yuyu Zhou, Jike Chen, Kangning Huang, Xiaojiang Gao, Rasmus Fensholt, Qihao Weng, & Weiqi Zhou

Abstract: Urban trees play a pivotal role in mitigating heat, yet the global determinants and patterns of their cooling efficiency (CE) remain elusive. Here, we quantify the diel CE of 229 cities across four climatic zones and employ a machine-learning model to assess the influence of variables on CE. We found that for every 10% increase in tree cover, surface temperatures are reduced by 0.25 °C during the day and 0.04 °C at night. Trees in humid regions exhibit the highest daytime CE, while those in arid zones demonstrate the greatest cooling effect at night. This can be explained by the difference in canopy density between the humid and arid zones. During the day, the high canopy density in the humid zone converts more solar radiation into latent heat flux. At night, the low canopy density in the arid zone intercepts less longwave radiation, which favors surface cooling. While climatic factors contribute nearly twice as much to CE as nonclimatic ones, our findings suggest that optimizing CE is possible by managing variables within specific thresholds due to their nonlinear effects. For instance, we revealed that in arid regions, an impervious surface coverage of approximately 60% is optimal, whereas in humid areas, reducing it to around 40% maximizes cooling benefits. These insights underscore the need for targeted management of nonclimatic factors to sustain tree cooling benefits and offer practical guidance for designing climate-resilient, nature-based urban strategies.

DOI: https://doi.org/10.1021/acs.est.4c14275

Our new paper, “Satellite-driven evidence of forest-induced temperature variability and its biophysical and biogeochemical pathways across latitudes“, is published in Ecological Indicators (IF: 7.0).

The paper can be downloaded at https://www.sciencedirect.com/science/article/pii/S1470160X25004753.

Authors: Zhaowu Yu, Mingchuan Shao, Wenjuan Ma, Chenghao Wang, & Jiachuan Yang

Abstract: Forests significantly influence local temperature dynamics, although the specifics of their impacts and mechanisms exhibit global variability. This study investigates the cooling or warming effects of global forests from 2001 to 2021 using multi-satellite data. The results indicate that (1) boreal forests exhibit a significant warming effect of +1.99 °C. Temperate forests exhibit nighttime warming but notable daytime cooling effect, resulting in a net daily cooling effect (−0.48 °C in the northern hemisphere, −0.91 °C in the southern hemisphere). The daily cooling effects peak in summer and gradually rise from spring to autumn, with winter exhibiting a warming inclination. Tropical forests consistently provide a cooling effect year-round (−2.11 °C). (2) Over the study period, tropical forests consistently revealed robust and stable cooling effects. Temperate forests displayed modest fluctuations in cooling effects, while the warming effect of boreal forest showed a slow trend upwards at a rate of +0.03 °C per year. (3) The warming effect of boreal forests is primarily due to NEE (net ecosystem exchange) and ET pathways (indirect effect: +0.253 and +0.392), while tropical forest cooling is driven by increased evapotranspiration (indirect effect: −0.938). As for temperate zones, annual cooling is primarily led by the NEE pathway (NH: −0.055 and SH: −0.415). (4) A robust annual coherence emerges between forests’ temperature regulation effects and ΔNEE, ΔET, and Δalbedo, where augmented ET and albedo significantly amplify cooling effects synchronously. The decrease in NEE exhibits a positive but non-synchronous impact on cooling at the local scale, while showing a strong and synchronous relationship with ΔLST at the global scale. These findings highlight the crucial role of forests in local temperature regulation, necessitating targeted management strategies.

DOI: https://doi.org/10.1016/j.ecolind.2025.113545

Our new paper, “Observation and simulation of methane plumes during the morning boundary layer transition“, is published in Journal of Geophysical Research: Atmospheres (IF: 3.8).

The paper can be downloaded at https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024JD042317.

Authors: Xiao-Ming Hu, Wesley Honeycutt, Chenghao Wang, Binbin Weng, Bowen Zhou, & Ming Xue

Abstract: Methane (CH₄) contributes significantly to global warming. However, accurate identification of CH₄ sources for reducing CH₄ emissions is often hampered by inadequate accuracy and spatiotemporal coverage of CH₄ detection, and lack of accurate CH₄ forward modeling used in top-down inversion systems. In this study, a field experiment was conducted in Pampa, Texas using two CH₄ sensors (LI-COR and OGI camera) to detect CH₄ releases. We investigated whether high-resolution simulations using the Weather Research and Forecasting (WRF) model with greenhouse gases (WRF-GHG) could accurately simulate the CH₄ plumes in the presence of evolving atmospheric boundary layer from sunrise to noon. CH₄ plumes showed substantial variation in time. At a release rate of ∼17.5 kg hr⁻¹, the maximum enhancement of CH₄ measured by LI-COR was 2.6 ppm at sunrise (7:36 a.m.), 250 m from the release location. Within half an hour after sunrise, this enhancement decreased to 0.3–0.4 ppm. The enhancement was 0.2 ppm by 10:00 a.m. and further dropped to less than 0.1 ppm after 11:30 a.m. Due to the low temperature at sunrise, the OGI camera failed to detect the CH₄ plume. The WRF-GHG large-eddy simulation (LES) with 32 m grid spacing successfully reproduced these CH₄ enhancements. In situ measurements together with numerical simulations illustrate the impact of the transition from a stable boundary layer in the early morning to a convective boundary layer at noon on the dispersion of CH₄ plumes. Additionally, CH₄ plumes from a cattle farm in Oklahoma are briefly examined using the same modeling approach.

DOI: https://doi.org/10.1029/2024JD042317

Our new paper, “Assessment of convection-permitting hydroclimate modeling in urban areas across the contiguous United States“, is published in Urban Climate (IF: 6.0). This work was led by undergraduate student Liam Thompson. Congratulations, Liam!

The paper can be downloaded at https://www.sciencedirect.com/science/article/pii/S2212095525000914.

Authors: Liam Thompson, Chenghao Wang, Cenlin He, Tzu-Shun Lin, Changhai Liu, and Jimy Dudhia

Abstract: Accurate representation of urban areas in weather and climate models is crucial for simulating interactions between urban surfaces and the atmospheric boundary layer, especially in high-resolution regional models that resolve deep convection. However, many continental-scale simulations use simplified urban parameterizations, raising questions about their ability to reproduce urban hydroclimate. This study evaluates CONUS404—a recent USGS-NCAR 4-km convection-permitting hydroclimate modeling dataset—in urban areas across the contiguous United States (CONUS). We assessed hourly near-surface air temperature, dewpoint, and wind speed simulations at 208 urban and 342 non-urban station locations from 2011 to 2020 using observations. Results show that CONUS404 performs better for air temperature in urban areas, with a slight mean warm bias (0.08 °C) at urban stations and a mean cold bias (−0.52 °C) at non-urban stations. Dewpoint simulations exhibit stronger dry biases at urban stations, suggesting underrepresented evapotranspiration from urban vegetation. Wind speed is generally underestimated, with average biases of −0.74 m s⁻¹ at urban and −0.35 m s⁻¹ at non-urban stations. Seasonal analyses reveal larger model errors for wintertime temperature and dewpoint that strongly depend on urban fraction. These findings highlight the limitations of the bulk urban parameterization in CONUS404, underscoring the need for enhanced urban representations to improve continental-scale hydroclimate simulations.

DOI: https://doi.org/10.1016/j.uclim.2025.102375

Our new paper, “Impact of urban trees on carbon dioxide exchange: Mechanistic pathways, environmental controls, and feedback“, is published in Journal of Environmental Management (IF: 8.0).

The paper can be downloaded at https://www.sciencedirect.com/science/article/pii/S0301479725000040.

Authors: Zhi-Hua Wang, Peiyuan Li, Chenghao Wang, & Xueli Yang

Abstract: The increase of carbon dioxide (CO2) concentration in the atmosphere is held responsible for global climate changes. To meet the objective of achieving carbon neutrality and keeping global warming in check, many cities, as hotspots of CO2 emissions, have been promoting the use of urban greenery, urban trees in particular, to mitigate carbon emissions from the built environment. However, there remain large uncertainty and divergence of the potential of urban trees for carbon mitigation, with the underlying mechanisms poorly understood. In this study, we conducted a comprehensive survey of the biophysical functions, their environmental controls, and possible heat-carbon-water feedback that mechanistically govern the CO2 exchange processes of trees in the built environment. This review helps to clarify some disparities and enables us to gain clearer insights into the participatory role of urban trees in the dynamics of CO2 exchange. In addition, we proposed a few guidelines for urban planning and management strategies of using trees to promote the sustainability of urban ecosystems.

DOI: https://doi.org/10.1016/j.jenvman.2025.124028

Our new paper, “CHUWD-H v1.0: a comprehensive historical hourly weather database for U.S. urban energy system modeling“, is published in Scientific Data (IF: 5.8).

The paper can be downloaded at https://www.nature.com/articles/s41597-024-04238-4.

Authors: Chenghao Wang, Chengbin Deng, Henry Horsey, Janet L. Reyna, Di Liu, Sarah Feron, Raúl R. Cordero, Jiyun Song, & Robert B. Jackson

Abstract: Reliable and continuous meteorological data are crucial for modeling the responses of energy systems and their components to weather and climate conditions, particularly in densely populated urban areas. However, existing long-term datasets often suffer from spatial and temporal gaps and inconsistencies, posing great challenges for detailed urban energy system modeling and cross-city comparison under realistic weather conditions. Here we introduce the Historical Comprehensive Hourly Urban Weather Database (CHUWD-H) v1.0, a 23-year (1998–2020) gap-free and quality-controlled hourly weather dataset covering 550 weather station locations across all urban areas in the contiguous United States. CHUWD-H v1.0 synthesizes hourly weather observations from stations with outputs from a physics-based solar radiation model and a reanalysis dataset through a multi-step gap filling approach. A 10-fold Monte Carlo cross-validation suggests that the accuracy of this gap filling approach surpasses that of conventional gap filling methods. Designed primarily for urban energy system modeling, CHUWD-H v1.0 should also support historical urban meteorological and climate studies, including the validation and evaluation of urban climate modeling.

DOI: https://doi.org/10.1038/s41597-024-04238-4

Database DOI: https://doi.org/10.17605/OSF.IO/5DP8E

Interactive Data Platform: https://arcg.is/COWWe

Our new paper, “Cooling efficacy of trees across cities is determined by background climate, urban morphology, and tree trait“, is published in Communications Earth & Environment (IF: 8.1).

The paper can be downloaded at https://www.nature.com/articles/s43247-024-01908-4.

Authors: Haiwei Li, Yongling Zhao, Chenghao Wang, Diana Ürge-Vorsatz, Jan Carmeliet, & Ronita Bardhan

Abstract: Urban planners and other stakeholders often view trees as the ultimate panacea for mitigating urban heat stress; however, their cooling efficacy varies globally and is influenced by three primary factors: tree traits, urban morphology, and climate conditions. This study analyzes 182 studies on the cooling effects of urban trees across 17 climates in 110 global cities or regions. Tree implementation reduces peak monthly temperatures to below 26 °C in 83% of the cities. Trees can lower pedestrian-level temperatures by up to 12 °C through large radiation blockage and transpiration. In tropical, temperate, and continental climates, a mixed-use of deciduous and evergreen trees in open urban morphology provides approximately 0.5 °C more cooling than a single species approach. In arid climates, evergreen species predominate and demonstrate more effective cooling within compact urban morphology. Our study offers context-specific greening guidelines for urban planners to harness tree cooling in the face of global warming.

DOI: https://doi.org/10.1038/s43247-024-01908-4

Our new paper, “Rapid decline in extratropical Andean snow cover driven by the poleward migration of the Southern Hemisphere westerlies“, is published in Scientific Reports (IF: 3.8).

The paper can be downloaded at https://www.nature.com/articles/s41598-024-78014-0.

Authors: Raúl R. Cordero, Sarah Feron, Alessandro Damiani, Shelley MacDonell, Jorge Carrasco, Jaime Pizarro, Cyrus Karas, Jose Jorquera, Edgardo Sepulveda, Fernanda Cabello, Francisco Fernandoy, Chenghao Wang, Alia L. Khan, & Gino Casassa

Abstract: Seasonal snow in the extratropical Andes is a primary water source for major rivers supplying water for drinking, agriculture, and hydroelectric power in Central Chile. Here, we used estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) to analyze changes in snow cover extent over the period 2001–2022 in a total of 18 watersheds spanning approximately 1,100 km across the Chilean Andes (27–36°S). We found that the annual snow cover extent is receding in the watersheds analyzed at an average pace of approximately 19% per decade. These alarming trends have impacted meltwater runoff, resulting in historically low river streamflows during the dry season. We examined streamflow records dating back to the early 1980s for 10 major rivers within our study area. Further comparisons with large-scale climate modes suggest that the detected decreasing trends in snow cover extent are likely driven by the poleward migration of the westerly winds associated with a positive trend in the Southern Annular Mode (SAM).

DOI: https://doi.org/10.1038/s41598-024-78014-0