通讯机构：
[Feng, C ] H;Hengyang Normal Univ, Coll Geog & Tourism, Hengyang 421002, Peoples R China.
关键词：
Event-based extreme precipitation;Time distribution pattern;Contribution rate of urbanization;Xiangjiang River Basin
摘要：
An in-depth understanding of event-based extreme precipitation (EEP), emphasizing precipitation process, can help to prevent the risk posed by regional high-intensity and persistent precipitation. The concept of time distribution pattern (TDP) is used to distinguish EEPs, which classifies EEPs according to the occurrence time of extreme precipitation. Furthermore, TDP1,2,3 is that the distribution of daily precipitation above the threshold is in the first half, in the second half, and both the first half and second half of EEP, respectively. We analyze temporal characteristics, spatial distribution, future trends of EEP, and the contribution rate of urbanization to EEP in this study. EEP thresholds exhibit a latitudinal gradient from central to northern and southern regions except for Nanyue Station (NY). TDP1 and TDP2 account for more than 60% among the total of EEPs. However, TDP3 is the dominant precipitation type observed at each station from the perspective of precipitation, intensity, duration, especially, in summer. EEP is less and TDP is unstable in autumn and winter. In general, there is an increasing trend in EEP and it is predicted that the trend of EEP will continue to rise. Moreover, the contribution rate of urbanization to EEP varies significantly, with a more pronounced inhibitory effect observed. The inhibitory effect of urbanization on the frequency and duration of TDP3 reached 60.83% and 72.77%, respectively. However, it is more significant on the extreme nature of TDP1 under urbanization, with a positive contribution rate of 9.63% and 21.83% to precipitation and intensity of TDP1, respectively. The results conclude that the higher the level of urbanization, the more pronounced the extreme trend of TDP1 becomes.
作者机构：
[Li, Suxun] Changan Univ, Sch Earth Sci & Resources, Xian 710054, Peoples R China.;[Feng, Chang; Yang, Liu; Li, Suxun] Hengyang Normal Univ, Coll Geog & Tourism, Hengyang 421002, Peoples R China.;[Feng, C] Hengyang Normal Univ, Coll Geog & Tourism, Hengyang 421002, Peoples R China.
通讯机构：
[Feng, C ] ;Hengyang Normal Univ, Coll Geog & Tourism, Hengyang 421002, Peoples R China.
关键词：
driving factors;evapotranspiration;MODIS;spatiotemporal patterns;standard deviation ellipse;Xiangjiang River Basin
摘要：
Evapotranspiration (ET) is a crucial parameter in the process of the hydrological cycle. It is of great significance for water resource management and the improvement of ecological systems in the Xiangjiang River Basin (XRB) to explore the spatial and temporal dynamic characteristics of ET. Based on MOD16, this study revealed the characteristics of spatial and temporal patterns of ET in the XRB from 2000 to 2020. We first applied land use data and change rate for overall trend analysis on ET. Then, we obtained spatiotemporal migration routes of ET through standard deviation ellipse (SDE). Furthermore, we demonstrated the effects of monsoon and urban expansion on ET change. Accordingly, we observed the following novel spatiotemporal patterns of ET: (1) while the ET of artificial surfaces decreased from 2000 to 2020, the change rate in most regions of the XRB was 8.83%, indicating that the overall trend of ET in the XRB was increasing. (2) At 10-year intervals, the SDE center of ET all migrated in a clockwise direction. (3) The correlation between precipitation and ET is more obvious than that between temperature and ET. (4) With the direct effects of monsoon on precipitation in East Asia, we found that the changes in precipitation are consistent with the ET change.
通讯机构：
[Feng, C ] H;Hengyang Normal Univ, Coll Geog & Tourism, Hengyang 421002, Peoples R China.
关键词：
river network system evolution;adaptation;urbanization;GTWR model;Xiangjiang River Basin
摘要：
<jats:p>The research focuses on the difficult problem of quantifying the adaptation state of river network system development under rapid urbanization. Based on the river network system data and remote sensing image data of the past 30 years, this study discusses the evolution of the river network system and its adaptability. The geographically and temporally weighted regression (GTWR) model was used to reveal the response of the river network system in the Xiangjiang River Basin to urbanization. The results suggest that the Xiangjiang River Basin has experienced a significant increase in urban land due to the strong disturbance by human activities in the last 25 years. The number indicators of river network system such as overall water surface rate and river network density have decreased by 10.04% and 13.99%, respectively. Drainage structure indicators such as tributary development coefficient and structural stability decreased by 6.89% and 4.40%, respectively. The influence of three-dimensional urbanization on the intensity of river network density change is spatiotemporal heterogeneity during 1995–2020. It shows that population factors have a significant negative impact on the upstream area. The regression coefficient between river network density and per capita GDP in the basin is positive. The regression coefficient of urban land is negative, indicating that urban expansion has a significant negative effect on river network density in Xiangjiang River basin. The analysis of the relationship between urbanization and river network system evolution by using the coordination degree model shows that: in the early stage, the level of urbanization is low, the adjustment capacity and carrying capacity of river network are strong, and the coordination degree of urbanization and river network system is small. The level of urbanization has reached a new height, especially in the upstream central cities such as Chang-Zhu-Tan from 2015 to 2020. At this time, the increase of coordination degree is characterized by the mutual promotion of urbanization and river network development, and the improvement of their adaptive development requirements. This study quantitatively reveals the changing characteristics and influencing factors of the adaptability of river network systems and urban spatial development, which can provide scientific support for regional human–water harmony, flood prevention and mitigation, and green urbanization development.</jats:p>
通讯机构：
[Yang, L ] H;Hengyang Normal Univ, Sch Geog & Tourism, Hengyang 421002, Peoples R China.
关键词：
Payments for water -related ecosystem services;Green water management;Green water compensation;Game theory;Scenario analysis
摘要：
Green water describes precipitation that infiltrates into the unsaturated soil layer and returns to the atmosphere via plant transpiration and soil evaporation, which are two functions of the hydrological cycle. Green water provides the basis for timber growth, crop production, and ecosystem services. However, it has not been adequately accounted for in traditional payments for water-related ecosystem services (PWES), which pre-dominantly consider on blue water and hence underestimate the availability of all water resources. In this study, a new framework of payments for green water-related ecosystem services (PGWES) is proposed based on green water management (GWM) and green water compensation (GWC). This framework is constructed with game theory modelling, hydrological simulation and scenario evaluation. Then, the Xiangjiang River Basin (XRB) is used as a case study to test and evaluate the feasibility of the framework. The results of this study are as follows: (a) the framework of PGWES and its game payoff matrix and optimal payoff function are improved by adding the GWM scenarios. This approach can identify the GWC standard and Pareto optimal solution in different GWM scenarios, thereby optimizing the spatial allocation of blue and green water in the river basin and coordinating conflicts of interest between the upstream and downstream. (b) The average Pareto optimal payoffs of the XRB are increased by 4390 million CNY/year under different GWM and GWC scenarios compared to the baseline scenario, and the average GWC standard is 2.41 CNY/m3 or 1305.98 CNY/hm2. The case study indicates that the socioeconomic and ecological benefits for the whole XRB are expected to significantly improve under this framework. (c) Three aspects of managing water resources and conflict of interest issues noted during the study include "broadening water sources", "saving water resources" and "coordinating water conflict". Green water resources are an important component in broadening water sources; green water management provides a basic measurement tool for saving water resources; and green water compensation based on game theory offers a possible way to coordinate water conflicts and should be given more attention. In general, the PGWES framework provides a referenced methodology for the efficient development and equitable allocation of blue and green water resources in the river basin; furthermore, this study provides a scientific basis for the theory and methods of PWES, thus enriching this field of research.
摘要：
Given environmental or hydrological functions influenced by changing river networks in the development of rapid urbanization, a clear understanding of the relationships between comprehensive urbanization (CUB) and river network characteristics (RNC), storage capacity (RSC), and regulation capacity (RRC) is urgently needed. In the rapidly urbanized Tai Lake Plain (TLP), China, various methods and multisource data were integrated to estimate the dynamics of RNC, RSC, and RRC as well as their interactions with urbanization. The bivariate Moran's I methods were applied to detect and visualize the spatial dependency of RNC, RSC, or RRC on urbanization. Geographically weighted regression (GWR) model was set up to characterize spatial heterogeneity of urbanization influences on RNC, RSC and RRC. Our results indicated that RNC, RSC and RRC variables each showed an overall decreasing trend across space from 1960s to 2010s, particularly in those of tributary rivers. RNC, RSC, or RRC had globally negative correlations with CUB, respectively, but looking at local scale the spatial correlations between each pair were categorized as four types: high-high, high-low, low-low, and low-high. GWR was identified to accurately predict the response of most RNC, RSC, or RRC variables to CUB (R-2: 0.6-0.8). The predictive ability of GWR was spatially non-stationary. The obtained relationships presented different directions and strength in space. All variables except for the water surface ratio (Wp) were more positively affected by CUB in the middle eastern parts of TLP. Drainage density, RSC and RRC variables were more negatively influenced by CUB in the northeast compared to other parts. The quantitative results of spatial relationships between urbanization and RNC, RSC or RRC can provide location-specific guidance for river environment protection and regional flood risk management.
期刊：
Journal of Geophysical Research: Atmospheres,2021年126(21):e2021JD035009-null ISSN：2169-897X
通讯作者：
Xiao, Mu
作者机构：
[Yu, Xiaoqin; Han, Longfei; Li, Zhongwu; Lv, Dianqing] Hunan Normal Univ, Coll Geog Sci, Changsha, Peoples R China.;[Xu, Youpeng] Nanjing Univ, Sch Geog & Oceanog Sci, Nanjing, Peoples R China.;[Deng, Xiaojun] Zhejiang Univ Finance & Econ, Sch Econ, Hangzhou, Peoples R China.;[Yang, Liu] Hengyang Normal Univ, Coll City & Tourism, Hengyang, Peoples R China.;[Lv, Dianqing] Jiangsu Univ Technol, Sch Chem & Environm Engn, Changzhou, Jiangsu, Peoples R China.
通讯机构：
[Xiao, Mu] A;Arizona State Univ, Sch Sustainable Engn & Built Environm, Tempe, AZ 85281 USA.
关键词：
urban heat island;long-term urbanization;WRF;Yangtze River Delta (YRD)
摘要：
In this study, we examined the summertime climatic effects of urban expansion during 1990–2010 in the Yangtze River Delta (YRD) region by analyzing station observations and performing numerical simulations with the Weather Research and Forecast (WRF) model. Long-term observations showed that urban area experienced a larger increase in summertime 2-m air temperature than rural part during 1980–2018, and the influence of urbanization on the urban-rural contrast was greater in the late stage (after 2000) than the early stage (before 2000). We applied the WRF model incorporated with historical land surface cover data (year 1990, 2000, and 2010) to further evaluate the climatic effects of long-term urbanization. On average, urban expansion over 1990–2010 led to 0.75°C increase in daily average temperature (1.06°C in daily minimum and 0.45°C in daily maximum) during the summer. The summertime daily temperature range decreased by 0.61°C in urban environment during the same period. Compared to the warming effect of urbanization in the 1990s, both the magnitude and affected area have increased after the millennium. Also, urban expansion reduced moisture in low-level atmosphere, and this urban dry island (UDI) effect was enhanced in the late stage. Less moisture in the atmosphere offset heat stress index induced by the warming temperature. We also found that the partitioning of net radiation between sensible and latent heat was the key factor that controlled urban warming effect.
Long-term urbanization-induced climate effects in Yangtze River Delta urban agglomeration region were examined based on analyzing observations and performing numerical simulations
Warming effect of urbanization was enhanced in both the magnitude and affected area in the late stage of urbanization
Altered energy partitioning between sensible and latent heat fluxes by urban expansion was the key factor of warming atmosphere
Urbanization is a long-term dynamic process, while the dynamic climatic effect of urbanization was seldom investigated. In this study, we used both long-term observations and simulations to examine the urban effect on summer climate in Yangtze River Delta. We found that urban daily average temperature increased by 0.75°C, and urban warming effect was greater in the late stage (after 2000) than the early stage (before 2000). Urbanization also caused air humidity loss, which made urban area drier and was known as urban dry island (UDI) effect. The change of heat stress was relatively small due to UDI effect. Urbanization resulted in increased sensible heat fluxes and reduced latent heat fluxes, which determined the urban warming effect. This study provides insights to understand warming air temperature in humid urban agglomeration.
期刊：
FRONTIERS IN EARTH SCIENCE,2021年9:677191 ISSN：2296-6463
通讯作者：
Yang, Liu
作者机构：
[Feng, Chang; Yang, Liu] Hengyang Normal Univ, Coll Geog & Tourism, Hengyang, Peoples R China.;[Han, Longfei] Hunan Normal Univ, Sch Geog Sci, Changsha, Peoples R China.
通讯机构：
[Yang, Liu] H;Hengyang Normal Univ, Coll Geog & Tourism, Hengyang, Peoples R China.
关键词：
Water Resources;Blue water;Green water;Climate Change;Parallel parameter calibration method;Prediction uncertainty;SWAT
摘要：
<jats:p>Green water resources, which are fundamental for plant growth and terrestrial ecosystem services, reflect precipitation that infiltrates into the unsaturated soil layer and returns to the atmosphere by plant transpiration and soil evaporation through the hydrological cycle. However, green water is usually ignored in water resource assessments, especially when considering future climate impacts, and green water modeling generally ignores the calibration of evapotranspiration (ET), which might have a considerable impact on green water resources. This study analyzes the spatiotemporal variations in blue and green water resources under historical and future climate change scenarios by applying a distributed hydrological model in the Xiangjiang River Basin (XRB) of the Yangtze River. An improved model calibration method based on remotely sensed MODIS ET data and observed discharge data is used, and the results show that the parallel parameter calibration method can increase the simulation accuracy of blue and green water while decreasing the output uncertainties. The coefficients (<jats:italic>p-factor</jats:italic>, <jats:italic>r-factor</jats:italic>, <jats:italic>KGE</jats:italic>, <jats:italic>NSE</jats:italic>, <jats:italic>R</jats:italic><jats:sup><jats:italic>2</jats:italic></jats:sup>, and <jats:italic>PBIAS</jats:italic>) indicate that the blue and green water projections in the calibration and validation periods exhibit good performance. Blue and green water account for 51.9 and 48.1%, respectively, of all water resources in the historical climate scenario, while future blue and green water projections fluctuate to varying degrees under different future climate scenarios because of uncertainties. Blue water resources and green water storage in the XRB will decrease (5.3–21.8% and 8.8–19.7%, respectively), while green water flow will increase (5.9–14.7%). Even taking the 95% parameter prediction uncertainty (95 PPU) range into consideration, the future increasing trend of the predicted green water flow is deemed satisfactory. Therefore, incorporating green water into future water resource management is indispensable for the XRB. In general, this study provides a basis for future blue and green water assessments, and the general modeling framework can be applied to other regions with similar challenges.</jats:p>
