@ The University of Oklahoma

Month: March 2024

New paper on urban irrigation published in Nature Communications

Our new paper, “The potential of urban irrigation for counteracting carbon-climate feedback“, is published in Nature Communications (IF: 16.6).

The paper and its supplement can be downloaded at https://www.nature.com/articles/s41467-024-46826-3.

Authors: Peiyuan Li, Zhi-Hua Wang, and Chenghao Wang

Abstract: Global climate changes, especially the rise of global mean temperature due to the increased carbon dioxide (CO2) concentration, can, in turn, result in higher anthropogenic and biogenic greenhouse gas emissions. This potentially leads to a positive loop of climate–carbon feedback in the Earth’s climate system, which calls for sustainable environmental strategies that can mitigate both heat and carbon emissions, such as urban greening. In this study, we investigate the impact of urban irrigation over green spaces on ambient temperatures and CO2 exchange across major cities in the contiguous United States. Our modeling results indicate that the carbon release from urban ecosystem respiration is reduced by evaporative cooling in humid climate, but promoted in arid/semi-arid regions due to increased soil moisture. The irrigation-induced environmental co-benefit in heat and carbon mitigation is, in general, positively correlated with urban greening fraction and has the potential to help counteract climate–carbon feedback in the built environment.

DOI: https://doi.org/10.1038/s41467-024-46826-3

Fig. 2: Governing mechanisms on carbon exchange of urban greenery. a A diagram showing carbon exchange of plants in the built environment with UHI, higher background CO2 concentration, and management (irrigation). b Irrigation-induced change of urban gross primary productivity (dGPPu), led by decrease of air temperature and increase of soil water content. c Irrigation-induced change of urban ecosystem respiration (dRu), led by decrease of soil temperature and increase of soil water content. d Irrigation-induced change of urban net ecosystem exchange (dNEEu), resulting from the combinations of dGPPu and dRu. e Urban ecosystem respiration as a function of soil temperature and soil water content. The light gray lines in b–d show all possible combinations lead to various types of outcomes. The black solid lines indicate pathway to the strong co-benefit effect. The red dashed lines indicate the pathway to the strong tradeoff effect. Circles in (e) indicate the average Ru before (hollow) and after (solid) irrigation. Arrows indicate the direction of change.

New paper on the cooling dynamics of urban vegetation published in Remote Sensing of Environment

Our new paper, “Enhanced observations from an optimized soil-canopy-photosynthesis and energy flux model revealed evapotranspiration-shading cooling dynamics of urban vegetation during extreme heat“, is published in Remote Sensing of Environment (IF: 13.5).

The paper and its supplement can be downloaded at https://www.sciencedirect.com/science/article/pii/S0034425724001093. The Share Link to download a copy is https://authors.elsevier.com/c/1ikad7qzT3Dj5 (valid through Apr 30, 2024).

Authors: Zhaowu Yu, Jiaqi Chen, Jike Chen, Wenfeng Zhan, Chenghao Wang, Wenjuan Ma, Xihan Yao, Siqi Zhou, Kai Zhu, and Ranhao Sun

Abstract: Previous studies on the cooling of urban vegetation mainly focused on its transpiration or shading effect separately, neglecting to explore the combined evapotranspiration-shading cooling. Further, accurate quantification of evapotranspiration-shading cooling remains challenging due to heterogeneity of urban landscapes, which limits understanding of its high-resolution spatiotemporal patterns. Here, we integrate high-precision remote sensing data and the Soil-Canopy-Observations of Photosynthesis and Energy Fluxes (SCOPE) model to propose an optimized quantitative approach. The approach was used to investigate changes in evapotranspiration-shade cooling during extreme heat. Taking Shanghai metropolitan as case, the results show: (1) The cooling capacity of urban vegetation in nighttime (18:00–6:00) is enhanced during extreme heat, which is attributed to accumulated effect of shading and enhanced evapotranspiration due to elevated vapor-pressure deficit. (2) In densely built-up areas with limited vegetation, there is a significant lack of thermal regulation, especially in the early morning (7:00) and late evening (17:00), thus exacerbating thermal stress. (3) At midday (11:00–13:00) there was a slight decrease in evaporative cooling, probably caused by the behaviour of the stomatal closure at high temperatures. Concurrently, high radiation causes the shading effect of vegetation to become more prominent, amplifying the cooling contrast between areas with dense and sparse vegetation cover. Moreover, the study also highlights that grassland with >50% cover can provide cooling effects similar to that of forest land. Overall, our study not only enhances the understanding of urban vegetation’s cooling effects but also underscores the importance of strategic urban vegetation planning in mitigating urban heat, particularly under the escalating frequency and intensity of heat waves.

DOI: https://doi.org/10.1016/j.rse.2024.114098

Fig. 5. Distribution patterns of urban vegetation evapotranspiration-induced cooling at typical moments of the daily cycle during heat waves in Shanghai.

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