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Unlocking the full potential of Sentinel-1 for flood detection in arid regions 充分释放哨兵-1 在干旱地区洪水探测方面的潜力
IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Pub Date : 2024-10-09 DOI: 10.1016/j.rse.2024.114417
Shagun Garg , Antara Dasgupta , Mahdi Motagh , Sandro Martinis , Sivasakthy Selvakumaran
Climate change has intensified flooding in arid and semi-arid regions, presenting a major challenge for flood monitoring and mapping. While satellites, particularly Synthetic Aperture Radar (SAR), allow synoptically observing flood extents, accurately differentiating between sandy terrains and water for arid region flooding remains an open challenge. Current global flood mapping products exclude arid areas from their analyses due to the sand and water confusion, resulting in a critical lack of observations which impedes response and recovery in these vulnerable regions. This paper explores the full potential of Sentinel-1 SAR to improve near-real-time flood mapping in arid and semi-arid regions. By investigating the impact of various parameters such as polarization, temporal information, and interferometric coherence, the most important information sources for detecting arid floods were identified. Using three distinct arid flood events in Iran, Pakistan, and Turkmenistan, different scenarios were constructed and tested using RF to evaluate the effectiveness of each feature. Permutation feature importance analysis was additionally conducted to identify key elements that reduce computational costs and enable a faster response during emergencies. Fusing VV coherence and amplitude information in pre-flood and post-flood imagery proved to be the most suitable approach. Results also show that leveraging crucial features reduces computational time by 35% as well as improves flood mapping accuracy by 50%. With advancements in cloud processing capabilities, the computational challenges associated with interferometric SAR computations are no longer a barrier. The demonstrated adaptability of the proposed approach across different arid areas, offers a step forward towards improved global flood mapping.
气候变化加剧了干旱和半干旱地区的洪灾,给洪灾监测和绘图带来了重大挑战。虽然卫星,特别是合成孔径雷达(SAR)可以同步观测洪水范围,但要准确区分干旱地区洪水的沙地和水域仍是一个公开的挑战。目前的全球洪水测绘产品由于混淆了沙地和水域而将干旱地区排除在分析范围之外,导致观测数据严重不足,阻碍了这些脆弱地区的应对和恢复工作。本文探讨了哨兵-1合成孔径雷达在改善干旱和半干旱地区近实时洪水测绘方面的全部潜力。通过研究偏振、时间信息和干涉相干性等各种参数的影响,确定了探测干旱洪水最重要的信息源。利用在伊朗、巴基斯坦和土库曼斯坦发生的三次不同的干旱洪水事件,构建了不同的情景,并使用射频进行了测试,以评估每个特征的有效性。此外,还进行了排列特征重要性分析,以确定可降低计算成本并在紧急情况下做出更快响应的关键要素。事实证明,在洪水前和洪水后的图像中融合 VV 相干性和振幅信息是最合适的方法。结果还表明,利用关键特征可将计算时间减少 35%,并将洪水测绘精度提高 50%。随着云处理能力的进步,与干涉测量合成孔径雷达计算相关的计算挑战已不再是障碍。所提出的方法在不同干旱地区的适应性得到了证明,为改进全球洪水测绘迈出了一步。
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引用次数: 0
Improved phenology-based rice mapping algorithm by integrating optical and radar data 通过整合光学和雷达数据改进基于物候的水稻绘图算法
IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Pub Date : 2024-10-09 DOI: 10.1016/j.rse.2024.114460
Zizhang Zhao , Jinwei Dong , Geli Zhang , Jilin Yang , Ruoqi Liu , Bingfang Wu , Xiangming Xiao
Information on rice planting areas is critically important for food and water security, as well as for adapting to climate change. Mapping rice globally remains challenging due to the diverse climatic conditions and various rice cropping systems worldwide. Synthetic Aperture Radar (SAR) data, which is immune to climatic conditions, plays a vital role in rice mapping in cloudy, rainy, low-latitude regions but it suffers from commission errors in high-latitude regions. Conversely, optical data performs well in high-latitude regions due to its high observation frequency and less cloud contamination but faces significant omission errors in low-latitude regions. An effective integrated method that combines both data types is key to global rice mapping. Here, we propose a novel adaptive rice mapping framework named Rice-Sentinel that combines Sentinel-1 and Sentinel-2 data. First, we extracted key phenological phases of rice (e.g., the flooding and transplanting phase and the rapid growth phase), by analyzing the characteristic V-shaped changes in the Sentinel-1 VH curve. Second, we identified potential flooding signals in rice pixels by integrating the VH time series from Sentinel-1 with the Land Surface Water Index (LSWI) and Enhanced Vegetation Index (EVI) from Sentinel-2, utilizing the generated phenology phases. Third, the rapid growth signals of rice following its flooding phase were identified using Sentinel-2 data. Finally, rice fields were identified by integrating flooding and rapid growth signals. The resultant rice maps in six different case regions of the world (Northeast and South China, California, USA, Mekong Delta of Vietnam, Sakata City in Japan, and Mali in Africa) showed overall accuracies over 90 % and F1 scores over 0.91, outperforming the existing methods and products. This algorithm combines the strengths of both optical and SAR time series data and leverages biophysical principles to generate robust rice maps without relying on any prior ground truth samples. It is well-positioned for global applications and is expected to contribute to global rice monitoring efforts.
水稻种植面积信息对于粮食和水安全以及适应气候变化至关重要。由于世界各地的气候条件各不相同,水稻种植系统也多种多样,因此绘制全球水稻地图仍具有挑战性。合成孔径雷达(SAR)数据不受气候条件的影响,在多云、多雨、低纬度地区的水稻测绘中发挥了重要作用,但在高纬度地区却存在误差。相反,光学数据由于观测频率高、云层污染少,在高纬度地区表现出色,但在低纬度地区却面临严重的遗漏误差。结合两种数据类型的有效综合方法是全球水稻测绘的关键。在此,我们提出了一种名为 Rice-Sentinel 的新型自适应水稻绘图框架,该框架结合了 Sentinel-1 和 Sentinel-2 数据。首先,我们通过分析 Sentinel-1 VH 曲线的特征性 V 形变化,提取了水稻的关键物候期(如淹水和插秧期以及快速生长期)。其次,我们利用生成的物候期,将 Sentinel-1 的 VH 时间序列与 Sentinel-2 的地表水指数(LSWI)和增强植被指数(EVI)进行整合,从而识别出水稻像素中潜在的洪涝信号。第三,利用 Sentinel-2 数据识别水稻在淹水阶段后的快速生长信号。最后,通过整合洪水和快速生长信号来识别稻田。在全球六个不同案例区域(中国东北和华南、美国加利福尼亚、越南湄公河三角洲、日本酒田市和非洲马里)绘制的水稻地图显示,总体准确率超过 90%,F1 分数超过 0.91,优于现有方法和产品。该算法结合了光学和合成孔径雷达时间序列数据的优势,并利用生物物理原理生成稳健的水稻地图,而无需依赖任何先验的地面实况样本。该算法可在全球范围内应用,有望为全球水稻监测工作做出贡献。
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引用次数: 0
Generation and evaluation of energy and water fluxes from the HOLAPS framework: Comparison with satellite-based products during extreme hot weather 从 HOLAPS 框架生成并评估能量和水通量:与极端炎热天气期间的卫星产品进行比较
IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Pub Date : 2024-10-09 DOI: 10.1016/j.rse.2024.114451
Almudena García-García, Jian Peng
Improving our understanding of the energy and water exchanges between the land surface and the lower atmosphere (i.e. land–atmosphere interactions), and how climate change may affect them, is crucial to predict changes in temperature and precipitation extremes. Observations of energy and water fluxes at the land surface are typically retrieved from the eddy covariance method, which presents limitations related to spatial and temporal gaps, and the non-closure of the energy and water balances. Meanwhile, soil moisture (SM) products derived from satellite data have been widely used at regional and global scales, but they are limited to capture only surface soil water content and variations. The combination of remote sensing (RS) data and modelling frameworks is called to be the solution to improve the spatial coverage and vertical resolution of land–atmosphere interactions data, ensuring the energy and water balance closure. Here, we explore the combination of remote sensing and meteorological data with a physical-based modelling framework, the High resOlution Land Atmosphere Parameters from Space (HOLAPS). We used HOLAPS to produce hourly consistent estimates of energy and water fluxes over Europe at 5 km resolution. HOLAPS and other satellite-based evapotranspiration and sensible heat flux products from the literature are evaluated against the water balance method and eddy covariance measurements. HOLAPS SM estimates together with other RS-modelling products are also evaluated against ground-based measurements at the surface and in the root zone. The evaluation of HOLAPS ET estimates show similar performance to the other products with Kling–Gupta efficiency (KGE) ¿ -0.41 in comparison with eddy covariance measurements from FLUXNET in all seasons but in boreal winter. The simulation of H is more uncertain than for ET with KGE values ranging from -2.5 to 0.8 along the products and stations at monthly scales. HOLAPS reaches slightly better results than the rest of ET and H products at daily scales in summer (KGE ¿ 0.3 for ET and KGE ¿ 0.0 for H) and during hot conditions (KGE ¿ 0.2 for ET and KGE ¿-0.2 for H), while the state-of-the-art products show KGE ¿ 0.1 for ET and KGE ¿ -0.41 for H in summer and KGE ¿ -0.1 for ET and KGE ¿ -0.6 for H during hot conditions. All products evaluated here yield a reasonable performance (KGE ¿-0.41 at most sites) in simulating SM at the surface and in the root zone. Our results expose the need for further investigating and improving product performances during extreme conditions. The good performance of HOLAPS together with its inherent advantages (RS data driven, high temporal and spatial resolution, spatial and temporal continuity, soil moisture at different depths and long-term consistent evapotranspiration and sensible heat flux estimates) support its use for agricultural and forest management activities as well as to study land–atmosphere interactions based on Earth Observations.
加深对陆地表面与低层大气之间的能量和水交换(即陆地-大气相互作用)以及气候变化可能对其产生的影响的了解,对于预测极端温度和降水的变化至关重要。对陆地表面能量和水通量的观测通常采用涡度协方差法,该方法存在时空差距以及能量和水量平衡不闭合等局限性。同时,从卫星数据中提取的土壤水分(SM)产品已在区域和全球范围内得到广泛应用,但它们仅限于捕捉地表土壤水分含量及其变化。遥感(RS)数据与建模框架的结合被认为是提高陆地-大气相互作用数据的空间覆盖率和垂直分辨率,确保能量和水分平衡闭合的解决方案。在此,我们探讨了遥感和气象数据与基于物理的建模框架--空间高分辨率陆地大气参数(HOLAPS)--的结合。我们利用 HOLAPS 以 5 千米的分辨率对欧洲的能量和水通量进行了每小时一致的估算。根据水平衡方法和涡度协方差测量结果,对 HOLAPS 和其他文献中基于卫星的蒸散和显热通量产品进行了评估。还根据地表和根区的地面测量结果对 HOLAPS SM 估计值和其他 RS 模拟产品进行了评估。与 FLUXNET 的涡度协方差测量结果相比,HOLAPS 的蒸散发估算结果在所有季节(寒带冬季除外)的表现都与其他产品相似,Kling-Gupta 效率 (KGE) ¿ -0.41。对 H 的模拟比对 ET 的模拟更不确定,在月尺度上,不同产品和站点的 KGE 值从-2.5 到 0.8 不等。在夏季(蒸散发的 KGE ¿ 0.3,蒸腾蒸发的 KGE ¿ 0.0)和炎热条件下(蒸散发的 KGE ¿ 0.2,蒸腾蒸发的 KGE ¿-0.2),HOLAPS 的日尺度结果略好于其他蒸散发和蒸腾蒸发产品,而最先进的产品在夏季蒸散发的 KGE ¿ 0.1,蒸腾蒸发的 KGE ¿ -0.41,在炎热条件下蒸散发的 KGE ¿ -0.1,蒸腾蒸发的 KGE ¿ -0.6。这里评估的所有产品在模拟地表和根区的土壤侵蚀时都有合理的表现(大多数地点的 KGE ¿-0.41)。我们的结果表明,有必要进一步研究和改进产品在极端条件下的性能。HOLAPS 的良好性能及其固有优势(RS 数据驱动、高时空分辨率、时空连续性、不同深度的土壤湿度以及长期一致的蒸散和显热通量估计值)支持将其用于农业和森林管理活动以及基于地球观测的土地-大气相互作用研究。
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引用次数: 0
An accuracy assessment of the surface reflectance product from the EMIT imaging spectrometer EMIT 成像光谱仪表面反射率产品的精度评估
IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Pub Date : 2024-10-07 DOI: 10.1016/j.rse.2024.114450
Red Willow Coleman , David R. Thompson , Philip G. Brodrick , Eyal Ben Dor , Evan Cox , Carlos Pérez García-Pando , Todd Hoefen , Raymond F. Kokaly , John M. Meyer , Francisco Ochoa , Gregory S. Okin , Daniela Heller Pearlshtien , Gregg Swayze , Robert O. Green
The Earth surface Mineral dust source InvesTigation (EMIT) is an imaging spectrometer launched to the International Space Station in July 2022 to measure the mineral composition of Earth’s dust-producing regions. We present a systematic accuracy assessment of the EMIT surface reflectance product in two parts. First, we characterize the surface reflectance product’s overall performance using multiple independent vicarious calibration field experiments with hand-held and automated field spectrometers. We find that the EMIT surface reflectance product has a standard error of ±1.0% in absolute reflectance units for temporally coincident observations. Discrepancies rise to ±2.7 % for spectra acquired at different dates and times of day, which we attribute mainly to changes in solar geometry. Second, we develop an error budget that explains the differences between EMIT and in-situ field spectrometer data. We find that uncertainties in spatial footprints, field spectroscopy, and the EMIT-reported measurement were sufficient to explain discrepancies in most cases. Our approach did not detect any systematic calibration or reflectance errors in the timespan considered. Together, these findings demonstrate that a space-based imaging spectrometer can acquire high-quality spectra across a wide range of observational and atmospheric conditions.
地球表面矿物尘源探测(EMIT)是 2022 年 7 月发射到国际空间站的成像光谱仪,用于测量地球产尘区的矿物成分。我们分两部分对 EMIT 表面反射率产品进行了系统的精度评估。首先,我们使用手持式和自动现场光谱仪进行了多个独立的替代校准现场实验,从而确定了表面反射率产品的整体性能。我们发现,对于时间上吻合的观测结果,EMIT 表面反射率产品的绝对反射率单位标准误差为 ±1.0±1.0%。在不同日期和时间获取的光谱,其差异上升到±2.7±2.7%,我们将其主要归因于太阳几何形状的变化。其次,我们制定了一个误差预算来解释 EMIT 和现场光谱仪数据之间的差异。我们发现,在大多数情况下,空间足迹、现场光谱仪和 EMIT 报告的测量值的不确定性足以解释差异。在所考虑的时间跨度内,我们的方法没有发现任何系统校准或反射误差。这些发现共同表明,天基成像光谱仪可以在广泛的观测和大气条件下获取高质量的光谱。
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引用次数: 0
Using river hypsometry to improve remote sensing of river discharge 利用河流湿度测量改进河流排泄量的遥感测量
IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Pub Date : 2024-10-07 DOI: 10.1016/j.rse.2024.114455
Michael Durand , Chunli Dai , Joachim Moortgat , Bidhyananda Yadav , Renato Prata de Moraes Frasson , Ziwei Li , Kylie Wadkwoski , Ian Howat , Tamlin M. Pavelsky
Remote sensing has the potential to dramatically advance river discharge monitoring globally, but precision of primary data (water surface elevation (WSE) and river width) remains a limiting factor. WSE can be measured from altimeters, and river width from imagers, but the measurements historically have not been made concurrently from space. This is changing with the advent of the Surface Water and Ocean Topography (SWOT) mission and is anticipated by the combination of high-resolution commercial imagery and DEMs from ArcticDEM. WSE and width respond to changing flow conditions as modulated by the three-dimensional structure of the river channel bed and banks. The relationship between WSE and width thus increases monotonically and is essentially the hypsometric curve of the river. In this study, we explore how simultaneous measurements of WSE and width, combined with the monotonic nature of the river hypsometric curve, can be used to improve measurements of river discharge. First, we present an algorithm to compute the river hypsometric curve from noisy measurements of WSE and width. Second, we demonstrate a method to compute estimates of WSE and width constrained to the river hypsometric curve, and we analyze the probability distribution function of the hypsometrically constrained WSE and width estimates. Specifically, we show that the variance of width and WSE is reduced by invoking a hypsometric constraint, at the cost of an induced correlation between the WSE and width errors. Third, we show that river discharge estimated with the hypsometrically constrained WSE and width is more precise than that without hypsometric constraint, and we predict the expected reduction in discharge error. Fourth, we look at six example river reaches measured by ArcticDEM. The WSE root mean square error had a median across the six reaches of 39.3 cm, which was improved to 33.4 cm across the six reaches using the hypsometric constraint. The discharge predictions were similarly improved: the constrained height and width produce more accurate discharge estimates for five of the six reaches and show reduced variation among flow laws. With the launch of SWOT, river hypsometry constraints applied to simultaneous measurement of WSE and width will support new discharge estimates globally.
遥感技术有可能在全球范围内极大地推动河流排放监测工作,但主要数据(水面高程(WSE)和河宽)的精确度仍然是一个限制因素。水面高程可以通过测高仪测量,河宽可以通过成像仪测量,但这些测量历来无法同时从太空进行。随着地表水和海洋地形图(SWOT)任务的到来,这种情况正在发生变化,预计高分辨率商业图像和 ArcticDEM 的 DEMs 将结合使用。在河床和河岸三维结构的调节下,WSE 和宽度会随着水流条件的变化而变化。因此,WSE 和宽度之间的关系是单调递增的,基本上就是河流的吸水性曲线。在本研究中,我们探讨了如何利用同时测量 WSE 和宽度以及河流吸水性曲线的单调性来改进河流排水量的测量。首先,我们提出了一种根据 WSE 和宽度的噪声测量值计算河流测湿曲线的算法。其次,我们演示了一种计算受河流吸水曲线约束的 WSE 和宽度估计值的方法,并分析了受吸水曲线约束的 WSE 和宽度估计值的概率分布函数。具体而言,我们表明,通过引用吸水性约束条件,宽度和 WSE 的方差减小了,但代价是 WSE 和宽度误差之间存在诱导相关性。第三,我们证明了使用受湿度约束的 WSE 和宽度估算的河流排放量比不使用湿度约束的更精确,并预测了排放量误差的预期减小。第四,我们以 ArcticDEM 测量的六条河流为例。六条河段的 WSE 均方根误差中位数为 39.3 厘米,使用湿度测量约束后,六条河段的 WSE 均方根误差中位数提高到 33.4 厘米。排泄量预测也得到了类似的改善:在六个河段中,有五个河段的高度和宽度约束条件下得出的排泄量估计值更为准确,并且流量规律之间的差异也有所减小。随着 SWOT 的推出,应用于同时测量 WSE 和宽度的河流湿度测量约束将支持全球范围内新的排放量估算。
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引用次数: 0
Individual tree species classification using low-density airborne multispectral LiDAR data via attribute-aware cross-branch transformer 通过属性感知交叉枝变换器利用低密度机载多光谱激光雷达数据进行单个树种分类
IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Pub Date : 2024-10-05 DOI: 10.1016/j.rse.2024.114456
Lanying Wang , Dening Lu , Linlin Xu , Derek T. Robinson , Weikai Tan , Qian Xie , Haiyan Guan , Michael A. Chapman , Jonathan Li
Traditional forest inventory supplies essential data for forest monitoring and management, including tree species, but obtaining individual tree-level information is increasingly crucial. Airborne Light Detection and Ranging (LiDAR) with multispectral observation offers rich information for improved forest inventory mapping with reliable individual tree attributes. Although deep learning techniques have shown promise in tree species classification, they are not sufficiently explored for individual tree-level classification using low-density (less than 30 point/m2) Airborne Multispectral LiDAR (AML) data. This study therefore explores the feasibility of using a deep learning (DL) framework for processing low-density AML point clouds to enhance tree species classification in challenging forest environments. A point-based deep learning network with a dual-branch mechanism combined Cross-Branch Attention modules named Attribute-Aware Cross-Branch (AACB) Transformer is designed for AML data to better differentiate tree species from delineated individual trees. In addition, a channel merging approach is introduced, which is suited to prepare the training samples of deep learning networks and reduces the computational costs. This study was tested with an average 9 points/m2 AML point cloud for 6 tree species including Populus tremuloides, Larix laricina, Acer saccharum, Picea abies, Pinus resinosa, and Pinus strobus from a Canadian mixed forest. The overall accuracies achieved 83.1 %, 85.8 %, and 95.3 % at species, genus, and leaf-type levels, respectively. The comparison between the proposed method and other widely used tree species classification methods demonstrates the effectiveness of the proposed approach in enhancing tree species classification accuracy. We discuss potentials and remaining challenges, and our findings allow to further improve tree species classification of low-density AML point clouds by DL technology.
传统的森林资源清查为森林监测和管理提供了包括树种在内的重要数据,但获取单棵树木级别的信息越来越重要。带有多光谱观测功能的机载光探测与测距(LiDAR)可提供丰富的信息,通过可靠的单棵树木属性改进森林资源清查制图。虽然深度学习技术在树种分类方面已显示出良好的前景,但在使用低密度(小于 30 点/平方米)机载多光谱激光雷达(AML)数据进行单棵树木级分类方面,还没有进行充分的探索。因此,本研究探索了使用深度学习(DL)框架处理低密度 AML 点云的可行性,以增强具有挑战性的森林环境中的树种分类。针对 AML 数据设计了一种基于点的深度学习网络,该网络具有双分支机制,结合了名为 "属性感知交叉分支(AACB)转换器 "的交叉分支注意模块,以便更好地从划定的单个树木中区分树种。此外,还引入了一种通道合并方法,该方法适用于准备深度学习网络的训练样本,并可降低计算成本。这项研究使用平均每平方米 9 个点的 AML 点云对加拿大混交林中的 6 个树种进行了测试,这些树种包括震颤杨(Populus tremuloides)、Larix laricina、糖槭(Acer saccharum)、枞树(Picea abies)、树脂松(Pinus resinosa)和石松(Pinus strobus)。在种、属和叶片类型层面,总体准确率分别达到 83.1%、85.8% 和 95.3%。该方法与其他广泛使用的树种分类方法进行了比较,证明了该方法在提高树种分类准确性方面的有效性。我们讨论了该方法的潜力和仍然存在的挑战,我们的发现有助于通过 DL 技术进一步改进低密度 AML 点云的树种分类。
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引用次数: 0
Surface energy balance-based surface urban heat island decomposition at high resolution 基于地表能量平衡的高分辨率地表城市热岛分解
IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Pub Date : 2024-10-05 DOI: 10.1016/j.rse.2024.114447
Fengxiang Guo , Jiayue Sun , Die Hu
Urban heat island (UHI) is among the most pronounced human impacts on Earth. To formulate locally adapted mitigation strategies, a comprehensive understanding of the influencing mechanisms of UHI at high resolution is imperative. Based on surface energy balance, we attributed surface UHI (SUHI) into five biophysical terms (surface radiation, anthropogenic heat, convection, evapotranspiration and heat storage term) using Sentinel-2 and Landsat-8 images in Beijing. The simulated SUHI intensity, derived by combining all five contribution terms, exhibited a good consistency but a higher spatial resolution, than SUHI intensity extracted from Landsat-8 land surface temperature product. SUHI intensity tended to decrease from the old city to outsides, attributed to the decrease of evapotranspiration, solar radiation and anthropogenic heat term. The convection and heat storage term play a positive role in reducing SUHI. Among urban morphological blocks, low-rise and high-density blocks had the strongest SUHI, with the evapotranspiration term contributing the most. The results highlighted the capacity of the urban surface to evaporate water in affecting Beijing SUHI. The proposed method provides one useful tool to analyze the drivers of SUHI from the aspect of heat formation, which can be potentially applied worldwide for large-scale comparisons of how urbanization affects UHI.
城市热岛(UHI)是人类对地球最明显的影响之一。要制定因地制宜的减缓战略,就必须以高分辨率全面了解 UHI 的影响机制。基于地表能量平衡,我们利用 Sentinel-2 和 Landsat-8 图像将地表 UHI(SUHI)归结为五个生物物理项(地表辐射、人为热量、对流、蒸散和蓄热项)。与从 Landsat-8 陆面温度产品中提取的 SUHI 强度相比,综合所有五个贡献项得出的模拟 SUHI 强度具有良好的一致性,但空间分辨率更高。SUHI 强度从老城区向城外呈下降趋势,这归因于蒸散、太阳辐射和人为热量项的减少。对流和蓄热项在降低 SUHI 方面发挥了积极作用。在城市形态区块中,低层和高密度区块的 SUHI 最大,蒸散项的贡献最大。结果凸显了城市地表水蒸发能力对北京 SUHI 的影响。所提出的方法为从热量形成的角度分析 SUHI 的驱动因素提供了一个有用的工具,可在全球范围内用于大规模比较城市化如何影响 UHI。
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引用次数: 0
Satellite-based estimation of monthly mean hourly 1-km urban air temperature using a diurnal temperature cycle model 利用昼夜温度周期模型对城市 1 公里每小时月平均气温进行卫星估算
IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Pub Date : 2024-10-04 DOI: 10.1016/j.rse.2024.114453
Fan Huang , Wenfeng Zhan , Zihan Liu , Huilin Du , Pan Dong , Xinya Wang
Cities worldwide face escalating climate change risks, underscoring the need for spatially and temporally resolved urban air temperature (Ta) data. While satellite-derived land surface temperature (LST) data have been widely used to estimate Ta, high-resolution hourly Ta estimation in urban areas remains underexplored. Traditional methods typically rely on LST data from geostationary satellites and continuous 24-h Ta observations from weather stations. To address these limitations, we introduce a method that combines a diurnal temperature cycle (DTC) model with a random forest model to estimate monthly mean hourly urban Ta at 1-km resolution. This approach leverages a limited number of diurnal Ta observations from weather stations, MODIS LST data, and ancillary information. The core idea of the proposed method is to transform the estimation of monthly mean hourly 1-km Ta into estimating 1-km DTC model parameters, primarily daily maximum and minimum Ta values. This method capitalizes on MODIS LST's ability to estimate daily Ta extremes and requires only four diurnal Ta observations within a daily cycle to estimate monthly mean hourly 1-km Ta. Station-based five-fold cross-validation yields overall RMSE values consistently below 1.0 °C across nine cities with diverse geographic and climatic contexts. The accuracy achieved with only four diurnal Ta observations rivals that obtained using continuous 24-h Ta observations. Even with a limited training set of ten stations, the overall RMSE remains below 1.0 °C for most cities. The proposed method proves effective for both single-city and multi-city modeling and can estimate daily hourly 1-km Ta under clear-sky conditions. In conclusion, this study offers a feasible, efficient, and versatile method for accurately estimating monthly mean hourly 1-km Ta, which can be readily applied to other cities and holds potential for various applications.
全世界的城市都面临着不断升级的气候变化风险,这就更加需要具有空间和时间分辨率的城市气温(Ta)数据。虽然源自卫星的陆地表面温度(LST)数据已被广泛用于估算气温,但城市地区的高分辨率每小时气温估算仍未得到充分开发。传统方法通常依赖于地球静止卫星的 LST 数据和气象站连续 24 小时的 Ta 观测数据。为了解决这些局限性,我们引入了一种将昼夜温度周期(DTC)模型与随机森林模型相结合的方法,以 1 千米的分辨率估算城市每小时的月平均 Ta 值。这种方法利用了气象站有限数量的昼夜气温观测数据、MODIS LST 数据和辅助信息。该方法的核心思想是将估算月平均每小时 1 公里 Ta 值转化为估算 1 公里 DTC 模型参数,主要是每日最大和最小 Ta 值。该方法利用了 MODIS LST 估算日极端 Ta 值的能力,只需在一个日周期内进行四次昼夜 Ta 观测,即可估算月平均每小时 1 公里 Ta 值。在地理和气候环境各异的九个城市中,基于站点的五倍交叉验证得出的总体 RMSE 值始终低于 1.0 °C。仅使用四个昼夜Ta观测数据所获得的准确度,可与使用连续24小时Ta观测数据所获得的准确度相媲美。即使使用有限的 10 个站点的训练集,大多数城市的总体 RMSE 仍低于 1.0 ℃。事实证明,所提出的方法对单个城市和多个城市的建模都很有效,并能在晴空条件下估算每日每小时 1 公里的 Ta 值。总之,本研究为精确估算月平均每小时 1 千米 Ta 值提供了一种可行、高效和通用的方法,该方法可随时应用于其他城市,并具有多种应用潜力。
{"title":"Satellite-based estimation of monthly mean hourly 1-km urban air temperature using a diurnal temperature cycle model","authors":"Fan Huang ,&nbsp;Wenfeng Zhan ,&nbsp;Zihan Liu ,&nbsp;Huilin Du ,&nbsp;Pan Dong ,&nbsp;Xinya Wang","doi":"10.1016/j.rse.2024.114453","DOIUrl":"10.1016/j.rse.2024.114453","url":null,"abstract":"<div><div>Cities worldwide face escalating climate change risks, underscoring the need for spatially and temporally resolved urban air temperature (T<sub>a</sub>) data. While satellite-derived land surface temperature (LST) data have been widely used to estimate T<sub>a</sub>, high-resolution hourly T<sub>a</sub> estimation in urban areas remains underexplored. Traditional methods typically rely on LST data from geostationary satellites and continuous 24-h T<sub>a</sub> observations from weather stations. To address these limitations, we introduce a method that combines a diurnal temperature cycle (DTC) model with a random forest model to estimate monthly mean hourly urban T<sub>a</sub> at 1-km resolution. This approach leverages a limited number of diurnal T<sub>a</sub> observations from weather stations, MODIS LST data, and ancillary information. The core idea of the proposed method is to transform the estimation of monthly mean hourly 1-km T<sub>a</sub> into estimating 1-km DTC model parameters, primarily daily maximum and minimum T<sub>a</sub> values. This method capitalizes on MODIS LST's ability to estimate daily T<sub>a</sub> extremes and requires only four diurnal T<sub>a</sub> observations within a daily cycle to estimate monthly mean hourly 1-km T<sub>a</sub>. Station-based five-fold cross-validation yields overall RMSE values consistently below 1.0 °C across nine cities with diverse geographic and climatic contexts. The accuracy achieved with only four diurnal T<sub>a</sub> observations rivals that obtained using continuous 24-h T<sub>a</sub> observations. Even with a limited training set of ten stations, the overall RMSE remains below 1.0 °C for most cities. The proposed method proves effective for both single-city and multi-city modeling and can estimate daily hourly 1-km T<sub>a</sub> under clear-sky conditions. In conclusion, this study offers a feasible, efficient, and versatile method for accurately estimating monthly mean hourly 1-km T<sub>a</sub>, which can be readily applied to other cities and holds potential for various applications.</div></div>","PeriodicalId":417,"journal":{"name":"Remote Sensing of Environment","volume":"315 ","pages":"Article 114453"},"PeriodicalIF":11.1,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142374397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Observation-based quantification of aerosol transport using optical flow: A satellite perspective to characterize interregional transport of atmospheric pollution 利用光流对气溶胶迁移进行基于观测的量化:从卫星角度描述区域间大气污染传输特征
IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Pub Date : 2024-10-03 DOI: 10.1016/j.rse.2024.114457
Tianhao Zhang , Yu Gu , Bin Zhao , Lunche Wang , Zhongmin Zhu , Yun Lin , Xing Chang , Xinghui Xia , Zhe Jiang , Hongrong Shi , Wei Gong
Interregional transport plays a significant role in haze formation with varying and disputable contribution extent. Current research on quantitatively analyzing interregional atmospheric pollution transport has mainly relied on meteorological and chemical models. However, these models are typically affected by uncertainties due to the assumptions and simplifications inherent in the numerical simulations and source emission estimations. In this study, a comprehensive optical flow framework is developed to offer a new perspective on quantitative characterization of interregional transport of atmospheric pollution based on synergistic observations from geostationary and sun-synchronous satellites. In this framework, the high-frequency continuous aerosol observing images are regarded as video in computer vision, and an aerosol dynamic optical flow algorithm is proposed by incorporating aerosol-specific assumptions and constraints, overcoming the limitation that traditional optical flow methods are typically confined to rigid bodies. Results demonstrate that the developed optical flow framework could distinguish the aerosol transport process from other dynamic processes of aerosol development and accurately capture the fast-changing details of transport processes. Moreover, the satellite-based optical flow framework achieves aerosol transport results comparable to those of widely accepted model-based methods, demonstrating the physical interpretation of pixel-based optical flow results and highlighting its effectiveness in quantitative characterization of the atmospheric pollution transport process via the Aerosol Transport Index (ATI). Furthermore, a case analysis of long-term assessments of interregional transport of atmospheric pollution indicates that Beijing acts as a “sink” of atmospheric pollution, and a downward trend could be found from the annually averaged transported aerosol net loadings due to the emission reduction policy. Compared with model-based methods, the satellite-based optical flow framework is directly grounded in observations and does not rely on emission inventories that take years to update. Therefore, it not only helps improve understanding the patterns of atmospheric pollution interregional transport, but also provides a more efficient and economical way to assess the effectiveness of regional joint control policy.
区域间传输在灰霾形成过程中扮演着重要角色,其贡献程度各不相同,且存在争议。目前,定量分析区域间大气污染传输的研究主要依赖气象和化学模型。然而,由于数值模拟和源排放估算中固有的假设和简化,这些模型通常会受到不确定性的影响。本研究基于地球静止卫星和太阳同步卫星的协同观测,建立了一个全面的光流框架,为定量描述大气污染的区域间传输提供了一个新的视角。在这一框架中,高频连续气溶胶观测图像被视为计算机视觉中的视频,通过纳入气溶胶特定的假设和约束条件,提出了气溶胶动态光学流算法,克服了传统光学流方法通常局限于刚体的局限性。结果表明,所开发的光学流框架能将气溶胶迁移过程与气溶胶发展的其他动态过程区分开来,并能准确捕捉迁移过程中快速变化的细节。此外,基于卫星的光学流框架所获得的气溶胶传输结果可与广泛接受的基于模型的方法相媲美,证明了基于像素的光学流结果的物理解释能力,并突出了其通过气溶胶传输指数(ATI)定量表征大气污染传输过程的有效性。此外,对区域间大气污染传输长期评估的案例分析表明,北京是大气污染的 "汇",从年均传输气溶胶净负荷中可以发现减排政策带来的下降趋势。与基于模型的方法相比,基于卫星的光流框架直接以观测数据为基础,不依赖于需要多年更新的排放清单。因此,它不仅有助于更好地理解大气污染的区域间传输模式,还为评估区域联合控制政策的有效性提供了一种更高效、更经济的方法。
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引用次数: 0
TIRVolcH: Thermal Infrared Recognition of Volcanic Hotspots. A single band TIR-based algorithm to detect low-to-high thermal anomalies in volcanic regions. TIRVolcH:火山热点热红外识别。一种基于单波段热红外的算法,用于探测火山区域从低到高的热异常。
IF 11.1 1区 地球科学 Q1 ENVIRONMENTAL SCIENCES Pub Date : 2024-10-03 DOI: 10.1016/j.rse.2024.114388
S. Aveni , M. Laiolo , A. Campus , F. Massimetti , D. Coppola
Detecting early signs of impending eruptions and monitoring the evolution of volcanic phenomena are fundamental objectives of applied volcanology, both essential for timely assessment of associated hazards. Thermal remote sensing proves to be a cost-effective, yet reliable, information source for these purposes, especially for the hundreds of volcanoes still lacking conventional ground-based monitoring networks. In this work, we present an innovative and effective single band TIR-based (11.45 μm) algorithm (TIRVolcH), capable of detecting thermal anomalies in a broad range of volcanic settings, from low-temperature hydrothermal systems to high-temperature effusive events. Based on the processing of Visible Infrared Imaging Radiometer Suite (VIIRS) scenes, the algorithm offers an unprecedented trade-off between spatial (375 m) and temporal resolution (multiple acquisitions per day), having the potential to detect thermal anomalies for pixel-integrated temperatures as low as 0.5 K above the background, while maintaining a false positive rate of ∼1.8 %. The analysis of decadal time series of VIIRS data (2012−2023), acquired at three different volcanoes, reveals how the algorithm can: (i) detect hydrothermal crises at fumarolic fields (Vulcano, Italy), (ii) unveil thermal unrest preceding dome extrusions and explosive eruptions (Agung, Indonesia), and (iii) spatially trace lava flows extent and quantify their advancement rate, as well as track their long-term cooling behaviour (La Palma, Spain).
We envisage that the algorithm will prove instrumental for detecting early signs of volcanic activity and following the evolution of eruptive phenomena, providing a useful tool for hazard management and risk reduction applications. Furthermore, the compilation of statistically robust multidecadal thermal datasets will provide novel insights and new perspectives into volcano monitoring, laying the ground for forthcoming higher-resolution TIR missions.
探测即将喷发的早期迹象和监测火山现象的演变是应用火山学的基本目标,对于及时评估相关危害都至关重要。事实证明,热遥感是实现这些目标的一种经济而可靠的信息来源,特别是对于仍然缺乏传统地面监测网络的数百座火山而言。在这项工作中,我们提出了一种创新而有效的基于可见光红外波段(11.45 μm)的单波段算法(TIRVolcH ),能够探测从低温热液系统到高温喷出事件等各种火山环境中的热异常。该算法以可见红外成像辐射计套件(VIIRS)场景处理为基础,在空间分辨率(375 米)和时间分辨率(每天多次采集)之间进行了前所未有的权衡,有可能探测到像素积分温度比背景低 0.5 千帕的热异常,同时保持 1.8%的误报率。对在三座不同火山获取的 VIIRS 数据十年时间序列(2012-2023 年)进行的分析揭示了该算法如何能够:(我们预计,该算法将被证明有助于探测火山活动的早期迹象和跟踪喷发现象的演变,为灾害管理和降低风险应用提供有用的工具。此外,统计上可靠的十年期热数据集的汇编将为火山监测提供新的见解和新的视角,为即将到来的更高分辨率热成像仪任务奠定基础。
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Remote Sensing of Environment
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