@ The University of Oklahoma

Category: New Publications

New paper on moisture sources of precipitation in the Tibetan Plateau published in Hydrology and Earth System Sciences

Our new paper, “Spatial distribution of oceanic moisture contributions to precipitation over the Tibetan Plateau“, is published in Hydrology and Earth System Sciences (IF: 6.617).

The paper and its supplement can be downloaded at https://hess.copernicus.org/articles/26/6413/2022/.

Authors: Ying Li, Chenghao Wang, Ru Huang, Denghua Yan, Hui Peng, and Shangbin Xiao

Abstract: Evaporation from global oceans is an important moisture source for glaciers and headwaters of major Asian rivers in the Tibetan Plateau (TP). Although the accelerated global hydrological cycle, the altered sea–land thermal contrast and the amplified warming rate over the TP during the past several decades are known to have profound effects on the regional water balance, the spatial distribution of oceanic moisture contributions to the vast TP remains unclear. This hinders the accurate quantification of regional water budgets and the reasonable interpretation of water isotope records from observations and paleo archives. Based on historical data and moisture tracking, this study systematically quantifies the absolute and relative contributions of oceanic moisture to long-term precipitation in the TP. Results show that the seasonal absolute and relative oceanic contributions are generally out of phase, revealing the previously underestimated oceanic moisture contributions brought by the westerlies in winter and the overestimated moisture contributions from the Indian Ocean in summer. Quantitatively, the relative contribution of moisture from the Indian Ocean is only ∼30 % in the south TP and further decreases to below 10 % in the northernmost TP. The absolute oceanic contribution exhibits a spatial pattern consistent with the dipole pattern of long-term precipitation trends across the Brahmaputra Canyon region and the central-northern TP. In comparison, relative oceanic contributions show strong seasonal patterns associated with the seasonality of precipitation isotopes across the TP.

DOI: https://doi.org/10.5194/hess-26-6413-2022

Fig. 8. Locations of the precipitation isotope monitoring stations and the relationship between the monthly relative IO moisture contributions (blue lines) and the precipitation isotope observations (dotted lines). Sites 1–13, 14–17 and 18–19 represent stations located within the monsoon domain, transition domain and westerlies domain, respectively. Blue lines show the mean IO moisture contributions based on three simulations, while the shadings show the range (detailed seasonal variations of three simulations are shown in Fig. S14). Note that for consistency, oceanic contributions below 10% and above 50% are not shown for sites 12 and 18.

New paper on vegetation response to climate change and human activities published in Ecological Indicators

Our new paper, “Vegetation dynamics influenced by climate change and human activities in the Hanjiang River Basin, central China“, is published in Ecological Indicators (IF: 6.263).

The Share Link to download a copy of our paper is https://authors.elsevier.com/sd/article/S1470-160X(22)01059-7 (valid until Dec 11, 2022).

Authors: Shaokang Yang, Ji Liu, Chenghao Wang, Te Zhang, Xiaohua Dong, and Yanli Liu

Abstract: Assessing the dynamics of vegetation and its response to environmental changes is essential to understanding ecosystem changes and the sustainable use of natural resources. In this study, we investigated the impacts of climate change and human activities on vegetation growth in the Hanjiang River Basin. We classified the basin into the portion mainly affected by climate change (VClimate) and the portion affected by both climate change and anthropogenic activities (VClimate+Human). Using an improved residual trend method that considers both lag effect and nonlinear response, we analyzed the relative contributions of climate change and human activities to observed NDVI changes. Results suggest that the basin experienced a statistically significant increase in growing-season NDVI during 2001–2016 (0.047 decade-1). Precipitation was the dominant climatic factor for NDVI change in VClimate+Human, whereas precipitation and temperature were nearly equally important for NDVI change in VClimate. On average, both climate change and human activities promoted vegetation growth during the study period, and their average contributions were 41.4 % and 15.5 %, respectively. In particular, climate change and human activities in general enhanced vegetation growth in non-urban areas, while human activities mainly reduced vegetation growth in urban areas. The findings of this study can benefit regional ecological restoration and environmental management projects.

DOI: https://doi.org/10.1016/j.ecolind.2022.109586

Fig. 8. Contributions of climate change and human activities to growing-season NDVI dynamics in the HJRB in 2001–2016: (a) contribution of precipitation and temperature change (C1 in both VClimate and VClimate+Human), (b) contribution of changes in climatic factors other than precipitation and temperature (C2 in VClimate), (c) contribution of changes in all climatic factors (C1 and C2 in VClimate and C1 in VClimate+Human), and (d) contribution of human activities (C2 in VClimate+Human). Solid circles in black (with names) in (d) are cities. The inset in each subplot shows the distribution of contributions.

New paper on urban thermal stress modeling published in Renewable and Sustainable Energy Reviews

Our new paper, “Realistic representation of city street-level human thermal stress via a new urban climate-human coupling system“, is published in Renewable and Sustainable Energy Reviews (IF: 16.799). This paper is from the collaboration with the Healthy Cities Laboratory at The University of Hong Kong.

The Share Link to download a copy of our paper is https://authors.elsevier.com/a/1flIY4s9Hw6370 (valid until Nov 03, 2022).

Authors: Xinjie Huang, Jiyun Song, Chenghao Wang, and Pak Wai Chan

Abstract: Urban overheating aggravated by climate change and rapid urbanization poses a severe threat to thermal health of urban residents. To more realistically represent street-level heat stress, we propose a new urban climate-human coupling system by integrating an advanced urban canopy model (UCM) with a new human-environment adaptive thermal stress (HEATS) module. The coupled UCM-HEATS system features a state-of-the-art solution to complicated human-street radiative exchanges and incorporates dynamic human thermoregulatory responses to microclimatic changes. The UCM-HEATS system was evaluated in a typical hot and humid city, Hong Kong, and then applied to investigate street-level thermal stress in various urban settings and under different personal conditions. By explicitly resolving shading effects of buildings and trees on human radiation budgets, our study emphasizes the marked effectiveness of active shade management using green and gray infrastructure on daytime heat mitigation, proposing a “right shade, right place, right time” paradigm for regulating important street canyon geometries (building height, road width, and tree crown width) and orientations. Additionally, human evaporative heat dissipation can be hindered by urban moisture islands and wind impediments; thus, a detailed urban ventilation strategy is suggested considering different temperature-humidity combinations. For personal heat protection, we identified an evident cooling effect of high-albedo clothing and a thermal-comfort-optimal walking speed. Special attention is paid to heat-vulnerable groups, especially older people who suffer from notably higher heat risks during pandemics with facemask-induced heat burden. Bridging urban climate and human ergonomics, this study aims to advance human-centric urban design toward future smart, resilient, and inclusive cities.

DOI: https://doi.org/10.1016/j.rser.2022.112919

Fig. 2. Schematic of the Urban Canopy Model-Human-Environment Adaptive Thermal Stress (UCM-HEATS) model.

New paper on causal urban climate network published in Journal of Environmental Management

Our new paper, “Detecting the causal influence of thermal environments among climate regions in the United States“, is published in Journal of Environmental Management (IF: 8.910). This paper is from the collaboration with the Urban Environment Research Group at Arizona State University (ASU). The first author, Xueli Yang, is a Ph.D. candidate at ASU. Congratulations to Xueli!

The Share Link to download a copy of our paper is https://authors.elsevier.com/c/1fepj14Z6tlDl~ (valid until Oct 15, 2022).

Authors: Xueli Yang, Zhi-Hua Wang, Chenghao Wang, and Ying-Cheng Lai

Abstract: The quantification of cross-regional interactions for the atmospheric transport processes is of crucial importance to improve the predictive capacity of climatic and environmental system modeling. The dynamic interactions in these complex systems are often nonlinear and non-separable, making conventional approaches of causal inference, such as statistical correlation or Granger causality, infeasible or ineffective. In this study, we applied an advanced approach, based on the convergent cross mapping algorithm, to detect and quantify the causal influence among different climate regions in the contiguous U.S. in response to temperature perturbations using the long-term (1901–2018) climatology of near surface air temperature record. Our results show that the directed causal network constructed by convergent cross mapping algorithm, enables us to distinguish the causal links from spurious ones rendered by statistical correlation. We also find that the Ohio Valley region, as an atmospheric convergent zone, acts as the regional gateway and mediator to the long-term thermal environments in the U.S. In addition, the temporal evolution of dynamic causality of temperature exhibits superposition of periodicities at various time scales, highlighting the impact of prominent low frequency climate variabilities such as El Niño–Southern Oscillation. The proposed method in this work will help to promote novel system-based and data-driven framework in studying the integrated environmental system dynamics.

DOI: https://doi.org/10.1016/j.jenvman.2022.116001

Fig. 3. Comparison of the correlation and causality networks for the nine CONUS climate regions: (a) the matrix of connectivity determined by undirected statistical correlation, (b) the matrix of connectivity determined by directed causality, and (c) graphic representation of causal and spurious links resulted from (a) and (b), with a threshold strength of 0.5. Cells with dashed boxes in (a) and (b) represent causally (above the threshold) connected pairs. The gray dashed lines represent the spurious link between different regions, and lines with an arrow the directed causal influence with strength denoted by different colors (the same scale as in (b)).

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