期刊：
Journal of Hydrology: Regional Studies,2024年52:101690 ISSN：2214-5818
通讯作者：
Zhang, XP
作者机构：
[Xiao, Xiong; Rao, Zhiguo; Li, Jiajie; Zhang, Xinping; Dai, Junjie; He, Xinguang; Zhang, Cicheng] Hunan Normal Univ, Coll Geog Sci, Changsha, Peoples R China.;[Xiao, Xiong; He, Xinguang; Zhang, Xinping] Hunan Normal Univ, Key Lab Geospatial Big Data Min & Applicat Hunan P, Changsha, Peoples R China.;[Liu, Na] Hengyang Normal Univ, Coll Geog & Tourism, Hengyang, Hunan, Peoples R China.
通讯机构：
[Zhang, XP ] H;Hunan Normal Univ, Coll Geog Sci, Changsha, Peoples R China.
关键词：
Stable isotopes;Seasonal origin index;Xylem water;Leaf water;Soil water
摘要：
Study region: From 2017 to 2019, xylem and leaf samples of Cinnamomum camphora were sampled and soil water samples at 0-100 cm depth were sampled 65 times simultaneously in a typical East Asian monsoon region. Study focus: The seasonal origin of plant and soil water from precipitation was inferred based on the stable isotope techniques, including the evaporation line slope (SEL) estimations and the seasonal origin index (SOI) calculation. New hydrological insights for the region: The regression SEL of leaf water was close to the theoretical SELs estimated based on the Craig-Gordon model, but xylem water and soil water showed higher regression SELs than the theoretical SELs, this may be due to the seasonality of the precipitation isotopes and evaporative fractionation. The fractionation-compensated isotopic values calculated based on the theoretical SELs of different water types were close, with the differences within 2.4%o for 618O and 20.0%o for 62H of each other, and the uncertainty of the fractionationcompensated isotopic values was low enough in the calculation of SOI. The SOI results showed that summer precipitation was more prevalent in plant and soil water, and more winter precipitation may recharge runoff when evapotranspiration demand is weak. Overall, the leaf sampling and the theoretical method have the potential to infer the seasonal water origin over a relatively long period.
作者机构：
School of Geospatial Engineering and Science, Sun Yat-sen University, Guangzhou 510275, China;Author to whom correspondence should be addressed.;[Haibo Zhang] College of Geography and Tourism, Hengyang Normal University, Hengyang 421002, China;[Jiejie Li; Fanyi Zhang] Department of Intelligent Transportation and Spatial Informatics, School of Transportation, Southeast University, Nanjing 211102, China;Key Laboratory of Safety and Risk Management on Transport Infrastructures, Ministry of Transport, PRC, Nanjing 210000, China
通讯机构：
[Mi Jiang] S;School of Geospatial Engineering and Science, Sun Yat-sen University, Guangzhou 510275, China<&wdkj&>Author to whom correspondence should be addressed.
摘要：
The accurate estimation of forest aboveground biomass is of great significance for forest management and carbon balance monitoring. Remote sensing instruments have been widely applied in forest parameters inversion with wide coverage and high spatiotemporal resolution. In this paper, the capability of different remote-sensed imagery was investigated, including multispectral images (GaoFen-6, Sentinel-2 and Landsat-8) and various SAR (Synthetic Aperture Radar) data (GaoFen-3, Sentinel-1, ALOS-2), in aboveground forest biomass estimation. In particular, based on the forest inventory data of Hangzhou in China, the Random Forest (RF), Convolutional Neural Network (CNN) and Convolutional Neural Networks Long Short-Term Memory Networks (CNN-LSTM) algorithms were deployed to construct the forest biomass estimation models, respectively. The estimate accuracies were evaluated under the different configurations of images and methods. The results show that for the SAR data, ALOS-2 has a higher biomass estimation accuracy than the GaoFen-3 and Sentinel-1. Moreover, the GaoFen-6 data is slightly worse than Sentinel-2 and Landsat-8 optical data in biomass estimation. In contrast with the single source, integrating multisource data can effectively enhance accuracy, with improvements ranging from 5% to 10%. The CNN-LSTM generally performs better than CNN and RF, regardless of the data used. The combination of CNN-LSTM and multisource data provided the best results in this case and can achieve the maximum R2 value of up to 0.74. It was found that the majority of the biomass values in the study area in 2018 ranged from 60 to 90 Mg/ha, with an average value of 64.20 Mg/ha.
作者机构：
[Lian-Tong Zhou] Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China;College of Earth Sciences, University of Chinese Academy of Sciences, Beijing, China;Ningxia Key Laboratory for Meteorological Disaster Prevention and Reduction, Yinchuan, China;Ningxia Meteorological Observatory, Yinchuan, China;College of Geography and Tourism, Hengyang Normal University, Hengyang, China
通讯机构：
[Lian-Tong Zhou] C;Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
关键词：
Rainfall;North China;Meridional SST gradient
摘要：
The rainfall over North China (NC) in July 2021 was the most since 1980, and coincided with a meridional gradient of sea surface temperature anomaly (MGSSTA) in the Pacific. The present study shows that the gradient between the positive sea surface temperature anomaly (SSTA) over the northwestern Pacific and the negative SSTA over the tropical central Pacific was the main reason for the enhanced rainfall in NC in July 2021 because of its influence on the anomalous northward movements of the western North Pacific anticyclone (WNPAC) and its southern cyclone. The associated easterly wind anomalies along the southern flank of the WNPAC converged with the anomalous easterly along the north flank of the anomalous cyclone, transporting more moisture from south to NC. Meanwhile, the MGSSTA likely induced an anomalous reversed Hadley circulation accompanied by distinct southerly wind anomalies in the low troposphere. These anomalies favored a strong monsoon circulation, which is often accompanied by a rain band in a more northern location.
摘要
2021年7月, 华北地区的降水量突破1980年以来的极值, 这与太平洋海温异常的经向梯度相吻合. 研究表明, 西北太平洋正海温异常与热带中太平洋负海温异常之间的梯度是2021年7月华北地区降水异常偏多的主要原因, 该梯度使得西北太平洋反气旋及其南部的气旋北移, 汇合的偏东风将大量水汽从海洋输送到华北地区, 使得华北地区降水偏多. 同时, 太平洋海温异常的经向梯度可能在对流层低层触发异常的反向哈德利环流, 伴随着南风异常, 使得季风环流增强, 雨带偏北.
关键词：
western North Pacific summer monsoon;tropical central-western Pacific;SST;interdecadal change
摘要：
This study reveals the strengthened interdecadal relationship between the western North Pacific summer monsoon (WNPSM) and tropical central-western Pacific sea surface temperature anomaly (SSTA) in summer after the early 1990s. In the first period (1979-91, P1), the WNPSM-related precipitation anomaly and horizontal wind anomaly present themselves as an analogous Pacific-Japan (PJ)-like pattern, generally considered to be related to the Nino-3 index in the preceding winter. During the subsequent period (1994-2019, P2), the WNPSM-related precipitation anomaly presents a zonal dipole pattern, correlated significantly with the concurrent SSTA in the Nino-4 and tropical western Pacific regions. The negative (positive) SSTA in the tropical western Pacific and positive (negative) SSTA in the Nino-4 region, could work together to influence the WNPSM, noting that the two types of anomalous SSTA configurations enhance (weaken) the WNPSM by the positive (negative) phase PJ-like wave and Gill response, respectively, with an anomalous cyclone (anticyclone) located in the WNPSM, which shows obvious symmetry about the anomalous circulation. Specifically, the SSTA in Nino-4 impacts the WNPSM by an atmospheric Gill response, with a stronger (weaker) WNPSM along with a positive (negative) SSTA in the Nino-4 region. Furthermore, the SSTA in the tropical western Pacific exerts an influence on the WNPSM by a PJ-like wave, with a stronger (weaker) WNPSM along with a negative (positive) SSTA in the tropical western Pacific. In general, SSTAs in the tropical western Pacific and Nino-4 areas could work together to exert influence on the WNPSM, with the effect most likely to occur in the El Nino (La Nina) developing year in P2. However, the SSTAs in the tropical western Pacific worked alone to exert an influence on the WNPSM mainly in 2013, 2014, 2016, and 2017, and the SSTAs in the Nino-4 region worked alone to exert an influence on the WNPSM mainly in Central Pacific (CP) La Nina developing years. The sensitivity experiments also can reproduce the PJ-like wave/Gill response associated with SSTA in the tropical western Pacific/Nino-4 regions. Therefore, the respective and synergistic impacts from the Nino-4 region and the tropical western Pacific on the WNPSM have been revealed, which helps us to acquire a better understanding of the interdecadal variations of the WNPSM and its associated climate influences.
作者机构：
[Deng, Zhiwei; Quan, Bin] Hengyang Normal Univ, Coll Geog & Tourism, Hengyang 421002, Peoples R China.;[Quan, Bin] Hengyang Base Int Ctr Space Technol Nat & Cultural, Hengyang 421002, Peoples R China.
通讯机构：
[Quan, B ] H;Hengyang Normal Univ, Coll Geog & Tourism, Hengyang 421002, Peoples R China.;Hengyang Base Int Ctr Space Technol Nat & Cultural, Hengyang 421002, Peoples R China.
关键词：
land use and land cover change;Intensity Analysis;change detection;Chang-Zhu-Tan Metropolitan Region
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.
关键词：
water storage;spatiotemporal change;driving factors;cryosphere;Three-River Headwaters Region
摘要：
Water storage (WS) is a crucial terrestrial ecosystems service function. In cold alpine regions (CAR), the cryosphere elements are important solid water resources, but the existing methods for quantitatively assessing WS usually ignore cryosphere elements. In this study, a revised Seasonal Water Yield model (SWY) in the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST), which considers the effects of frozen ground (FG) and snow cover (SC) on WS, was employed to estimate the spatiotemporal distribution and changes in WS in the Three-Rivers Headwaters region (TRHR) from 1981 to 2020. Sensitivity analyses were conducted to understand the overall effects of multiple factors on WS, as well as the dominant driving factors of WS change at the grid scale in the TRHR. The results show that (1) the WS in the TRHR generally increased from 1981 to 2020 (0.56 mm/year), but the spatial distribution of WS change varied greatly, with a significant increasing trend in the northwest part and a significant decreasing trend in the southeast part. (2) In the last 40 years, increased precipitation (Pre) positively affected WS, while increased potential evapotranspiration (ET0) reduced it. Increased permeability caused by degradation of frozen ground increased WS, while snow cover and LULC changes reduced it. (3) In the TRHR, Pre primarily affected the WS with the largest area ratio (32.62%), followed by land use/land cover (LULC) (19.69%) and ET0 (18.49%), with FG being fourth (17.05%) and SC being the least (6.64%). (4) The highly important and extremely important zones generally showed a decreasing trend in WS and should be treated as key and priority conservation regions. It is expected that this research could provide a scientific reference for water management in the TRHR.
