
Shengbiao WuThe University of Hong Kong | HKU · Faculty of Architecture
Shengbiao Wu
PhD
About
57
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Introduction
Publications
Publications (57)
Greenspace plays a crucial role in urban ecosystems and has been recognized as a key factor in promoting sustainable and healthy city development. Recent studies have revealed a growing concern about urban greenspace exposure inequality; however, the extent to which urbanization affects human exposure to greenspace and associated inequalities over...
Quantification of large-scale leaf age-dependent leaf area index has been lacking in tropical and subtropical evergreen broadleaved forests (TEFs) despite the recognized importance of leaf age in influencing leaf photosynthetic capacity in this region. Here, we simplified the canopy leaves of TEFs into three age cohorts, i.e., young, mature and old...
Increasing exposure to heat stress threatens the health and well-being of urban residents. However, existing studies on measuring human thermal comfort exposure remain uncertain without considering fine-scale human-heat interaction and its long-term dynamics. To inform this issue, we proposed a population-weighted exposure assessment framework with...
Land surface albedo plays an important role in controlling the surface energy budget and regulating the biophysical processes of natural dynamics and anthropogenic activities. Satellite remote sensing is the only practical approach to estimate surface albedo at regional and global scales. It nevertheless remains challenging for current satellites t...
Intensifying wildfires and human settlement expansion have placed more people and infrastructure at the wildland–urban interface (WUI) areas under risk. Wildfire management and policy response are needed to protect ecosystems and residential communities; however, maps containing spatially explicit information on the distribution of WUI areas are li...
PlanetScope CubeSats data with a 3-m resolution, frequent revisits, and global coverage have provided an unprecedented opportunity to advance land surface monitoring over the recent years. Similar to other optical satellites, cloud-induced data missing in PlanetScope satellites substantially hinders its use for broad applications. However, effectiv...
The United Nations specified the need for “providing universal access to greenspace for urban residents” in the 11th Sustainable Development Goal. Yet, how far we are from this goal remains unclear. Here, we develop a methodology incorporating fine-resolution population and greenspace mappings and use the results for 2020 to elucidate global differ...
Greenspace exposure metrics can allow for comparisons of green space supply across time, space, and population groups, and for inferring patterns of variation in opportunities for people to enjoy the health and recreational benefits of nearby green environments. A better understanding of greenspace exposure differences across various spatial scales...
Anisotropic canopy reflectance plays a crucial role in estimating vegetation biophysical parameters, whereas soil reflectance anisotropy affects canopy reflectance. However, woodland canopy bidirectional reflectance distribution function (BRDF) models considering soil anisotropy are far from universal, especially for the BRDF models of mountain for...
Land surface albedo is a crucial variable of earth energy budget and global climate change. Rugged terrain significantly impacts surface Bidirectional Reflectance Distribution Function (BRDF) and the subsequent albedo retrieval using satellite remote sensing. Existing studies of estimating surface BRDF/albedo from satellite observations are limited...
Land surface temperature (LST) is listed as an essential climate variable (ECV) and supports quantitative estimates of the energy budget while serving as a proxy for measuring the effects of climate change and extreme events. Forested areas are considered a major land unit impacted by temperature rise; therefore, thorough monitoring is mandatory. A...
Tropical leaf phenology—particularly its variability at the tree-crown scale—dominates the seasonality of carbon and water fluxes. However, given enormous species diversity, accurate means of monitoring leaf phenology in tropical forests is still lacking. Time series of the Green Chromatic Coordinate (GCC) metric derived from tower-based red–greenb...
A comprehensive assessment of satellite-derived albedo products is undeniably essential for better use consideration and the further refinement of the retrieval algorithm. Although satellite albedo products have been extensively validated over spatially homogeneous areas, it remains a challenge to validate them over rugged terrain. Consequently, th...
A comprehensive assessment of satellite-derived albedo products is undeniably essential for better use consideration and the further refinement of the retrieval algorithm. Although satellite albedo products have been extensively validated over spatially homogeneous areas, it remains a challenge to validate them over rugged terrain. Consequently, th...
Disentangling the individual contributions from vegetation and soil in measured canopy reflectance is a grand challenge to the remote sensing and ecophysiology communities. Since Solar Induced chlorophyll Fluorescence (SIF) is uniquely emitted from vegetation, it can be used to evaluate how well reflectance-based vegetation indices (VIs) can separa...
PlanetScope satellite data with a 3-m resolution and near-daily global coverage have been increasingly used for land surface monitoring, ranging from land cover change detection to vegetative biophysics characterization and ecological assessments. Similar to other satellite data, effective screening of clouds and cloud shadows in PlanetScope images...
The microclimate dynamics under forest crown fundamentally drive plant community responses to global warming. The understory air and soil temperatures are two of the most important components of forest understory microclimate. However, there is rare method to reasonably evaluate the joint effects of forest cover on the understory air and soil tempe...
Climatic drivers for canopy leaf shedding and flush of evergreen broadleaved forest biome are still unclear at the continental scale across tropical and subtropical region. This imposes a challenge for modeling pantropical photosynthesis seasonality in Earth system models. Here, we examined three potential climatic triggers, vapor pressure deficit–...
Relationships among productivity, leaf phenology, and seasonal variation in moisture and light availability are poorly understood for evergreen broadleaved tropical/subtropical forests, which contribute 25% of terrestrial productivity. On the one hand, as moisture availability declines, trees shed leaves to reduce transpiration and the risk of hydr...
Abstract Droughts cause extreme anomalies in tropical forest growth, but the direction and magnitude of tropical forests in response to droughts are still widely debated. Here, we used four satellite‐based canopy growth proxies (CGPs), including three optical and one passive microwave, and in situ fluxes observations from eddy covariance (EC) measu...
Leaf trait relationships are widely used to predict ecosystem function in Terrestrial Biosphere Models (TBMs), in which leaf maximum carboxylation capacity (Vc,max), an important trait for modelling photosynthesis, can be inferred from other easier-to-measure traits. However, whether trait-Vc,max relationships are robust across different forest typ...
The estimation of satellite-based albedo highly depends on the surface reflectance (SR). In mountainous areas, three types of SRs [i.e., the virtual SR (VSR) that is retrieved from the atmospheric correction model, the topographically corrected SR (TCSR) that is retrieved from the atmospheric and topographic correction model, and the sloping SR (SS...
In temperate forests, autumn leaf phenology signals the end of leaf growing season and shows large variability across tree-crowns, which importantly mediates photosynthetic seasonality, hydrological regulation, and nutrient cycling of forest ecosystems. However, critical challenges remain with the monitoring of autumn leaf phenology at the tree-cro...
Most surface-atmosphere radiative transfer models (RTMs) work only for flat surfaces, with the exception being time-consuming 3-D scene-based models. The deficiency of flat-surface RTMs that do not consider topographic effects is that their applications in earth observation and simulation studies are impaired because rugged terrains make up approxi...
Leaf optical spectra reflect the combination of leaf biochemical, morphological and physiological properties, and play an important role in many ecological and Earth system processes. Radiative transfer models are widely used to simulate leaf spectra by quantifying photon transfer processes of reflection, transmission and absorption within a plant...
Topographic and angular corrections on Sentinel-2 imagery are crucial for the generation of consistent surface reflectance. We propose a novel topographic-angular integrated normalization approach based on the combination of the path length correction (PLC) and C-factor approaches. The PLC-C normalization approach is a semiphysical method with limi...
In tropical forests, leaf phenology-particularly the pronounced dry-season green-up-strongly regulates bio-geochemical cycles of carbon and water fluxes. However, uncertainties remain in the understanding of tropical forest leaf phenology at different spatial scales. Phenocams accurately characterize leaf phenology at the crown and ecosystem scales...
Topographic correction is a prerequisite for generating radiometrically consistent Landsat 8 OLI vegetation reflectances in support of temporally continuous and spatially mosaicked applications. Path length correction (PLC) is a physically solid topographic correction method that avoids the involvement of any empirical parameter and is therefore su...
Semi-empirical, kernel-driven linear BRDF models are widely used to characterize vegetation reflectance anisotropy and provide land surface BRF products at the regional and global scales. However, these models usually imply an assumption of spherical leaf inclination. The effects of such an ideal assumption on simulating surface BRF remain few quan...
As an essential climate variable (ECV), land surface albedo plays an important role in the Earth surface radiation budget and regional or global climate change. The Tibetan Plateau (TP) is a sensitive environment to climate change, and understanding its albedo seasonal and inter-annual variations is thus important to help capture the climate change...
Validation of remote sensing albedo products involves comparisons between point-scale in situ observations and footprint-scale satellite retrievals. However, the observed differences between product and in situ observations are not only attributable to intrinsic errors of satellite products but also to inadequate spatial representativeness of in si...
Comprehensively evaluating the accuracy of the digital elevation model (DEM) upscaling methods is significant for us to choose the DEM upscaling method reasonably, master the DEM upscaling law, and construct a new DEM upscaling model. However, the current researches on DEM accuracy evaluation are still not sufficient to meet the requirements of pra...
The anisotropic scattering behavior of land surface is characterized by its bidirectional reflectance-distribution function (BRDF). However, a physically consistent BRDF definition is still lacking for heterogeneous and rugged terrain that accounts for approximately 24% of Earth's land surface. In this study, we revisited current BRDF definitions a...
Rugged terrain complicates the BRDF modeling mainly by the modulation of sun-target-sensor geometry and shadowing effects. An improved kernel-driven BRDF model coupled with topography (KDCT) is put forward by combining the RTLSR model used in the algorithm for MODIS bidirectional reflectance anisotropies of land surface (AMBRALS) and the anisotropi...
To study regional climate change and sea surface temperature (SST) variations in the South China Sea, three tree-ring width index chronologies (whole ring width, earlywood width and latewood width) of the Pinus massoniana from Changting, Fujian, in Southeast China were built. A correlation analysis was conducted between the chronologies and climate...
This paper presents a simple radiative transfer model based on spectral invariant properties (SIP). The canopy structure parameters, including the leaf angle distribution and multi-angular clumping index, are explicitly described in the SIP model. The SIP model has been evaluated on its bidirectional reflectance factor (BRF) in the angular space at...
Accurately estimating the spatial-temporal distribution of downward surface shortwave radiation (DSSR) is essential for terrestrial ecological modeling and climate change research. The accurate georegistration of digital elevation model (DEM) has become one of the significant bottlenecks for improving the DSSR accuracy over rugged terrain. To clear...
Presents corrections to the paper, “Algorithms for calculating topographic parameters and their uncertainties in downward surface solar radiation (DSSR) estimation,” (Wu, S., et al), IEEE Geosci. Remote Sens. Lett., vol. 15, no. 8, pp. 1149–1153, Aug. 2017.
Topographic effects on canopy reflectance play a pivotal role in the retrieval of surface biophysical variables over rugged terrain. In this paper, we proposed a new canopy anisotropic reflectance model for discrete forests, Geometric Optical and Mutual Shadowing and Scattering-from-Arbitrarily-Inclined-Leaves model coupled with Topography (GOSAILT...
Rugged terrain distorts optical remote sensing signals, and land-cover classification and biophysical parameter retrieval over mountainous regions must account for topographic effects. Therefore, topographic correction is a prerequisite for many remote sensing applications. In this study, we proposed a semi-physically based and simple topographic c...
The importance of the bidirectional reflectance distribution function (BRDF) has been well documented in quantitative remote sensing. The semiempirical, kernel-driven BRDF model is widely used to generate operational BRDF/albedo products due to its simplicity and accuracy. However, the effect of topography is rarely coupled with a kernel-based BRDF...
In situ albedo measurement over sloped surfaces is pivotal to a wide range of remote sensing applications, such as the estimation and evaluation of surface energy budget at regional and global scales. However, existing albedo measurements over rugged terrain are limited and controversial and remain a major challenge. In this paper, two commonly mea...
The scale effect is a common phenomenon in geography that restricts the development of space science, such as remote sensing. Scale issues have elicited increasing attention from scientists due to the development of quantitative remote sensing. Developing a reasonable scaling method to promote the extensive application of remote sensing technology...
Downward surface solar radiation (DSSR) plays an important role in the earth's surface energy budget. However, it has significant spatial-temporal heterogeneity over the rugged terrain. To accurately capture DSSR, many analytical terrain parameter algorithms based on digital elevation models (DEMs) have been proposed. However, the uncertainties of...
Heterogeneous terrain significantly complicates signals received by airborne or satellite sensors. It has been demonstrated that both solar direct beam and diffuse skylight illumination conditions are significant factors influencing the anisotropy of reflectance over mountainous areas. Several models and methods have been developed to account for t...
Rugged terrain, including mountains, hills, and some high lands are typical land surfaces around the world. As a physical parameter for characterizing the anisotropic reflectance of the land surface, the importance of the bidirectional reflectance distribution function (BRDF) has been gradually recognized in the remote sensing community, and great...
Topography complicates the modeling and retrieval of land surface albedo due to shadow effects and the redistribution of incident radiation. Neglecting topographic effects may lead to a significant bias when estimating land surface albedo over a single slope. However, for rugged terrain, a comprehensive and systematic investigation of topographic e...
The issue for the validation of land surface remote sensing albedo products over rugged terrain is the scale effects between the reference albedo measurements and coarse scale albedo products, which is caused by the complex topography. This paper illustrates a multi-scale validation strategy specified for coarse scale albedo validation over rugged...
Geometric-optical (GO) model suitable for forest plantation (GOFP) is a GO model for forest plantations at the stand level developed in this study based on a four-scale GO model a Geometric-Optical Model for Sloping Terrains-II (GOST2), which simulates the bidirectional reflectance distribution function (BRDF) for natural forest canopies. In most p...
Current bidirectional reflectance distribution function (BRDF) inversions using ordinary least squares (OLS) criterion can be easily contaminated by observations with residual cloud and undetected high aerosols, which leads to abrupt fluctuations in the normalized difference vegetation index (NDVI) time series. The OLS criterion assumes the noise h...
The development of near-surface remote sensing requires the accurate extraction of leaf area index (LAI) from networked digital cameras under all illumination conditions. The widely used directional gap fraction model is more suitable for overcast conditions due to the difficulty to discriminate the shaded foliage from the shadowed parts of images...
Projects
Projects (3)
Special Issue Information
https://www.mdpi.com/journal/remotesensing/special_issues/Surface_Biophysical_Parameter_Retrieval
Dear Colleagues,
Surface biophysical parameters across leave (e.g., leaf chlorophyll nitrogen and water contents, leaf mass per area, and leaf inclination angle), canopy (e.g., canopy leaf area index, height and biomass, and tree crown area, and diameter at breast height), and landscape (e.g., surface albedo, temperature, and radiative budget) scales are crucial for modeling terrestrial processes, monitoring agricultural ecosystems, and quantifying many human–environment interactions. Remote sensing has become the mainstream technology for retrieving and mapping large-scale and long-term biophysical surface parameters. Their successful retrievals using remote sensing rely on accurate physical models, robust retrieval approaches, high-quality data observations, and reliable validation strategies. Therefore, advances are needed to better monitor the biophysical surface parameters, and to also improve our understanding and modeling of terrestrial ecosystems processes and human–nature relationships.
This Special Issue aims to report on the state-of-the-art in the monitoring of biophysical surface parameters with remote sensing. Related articles are welcome, including, but not limited to, the following topics:
Physical models (e.g., 1-D and 3-D) across multi-scales (e.g., leaf, canopy, individual tree-crown, ecosystem, landscape, and rugged terrain) for modeling remote sensing signals integrated with surface biophysical parameters.
Experimental sources of inaccuracy when retrieving surface biophysical parameters from remote sensing observations: atmosphere conditions, geometric configuration of observation, directional and neighborhood effects, 3-D architecture of the studied landscape, etc.
Retrieval approaches (e.g., empirically based, physically based, and machine learning and deep learning approaches) across multi-scale observation platforms (e.g., smartphone, wireless sensor network (WSN), tower-based cameras, unmanned aerial vehicle (UAV), airborne, and satellite) for retrieving surface biophysical parameters.
New proposed or improved operational algorithms for recent satellite missions (e.g., Himawari-8, DSCOVR EPIC, Landsat-8, Sentinel-2, Worldview, PlanetScope, and PRISMA) to large-scale map surface biophysical parameters.
Rapid estimation approaches using the cloud-computing platforms (e.g., Google Earth Engine (GEE), Amazon Web Services (AWS), and Microsoft Azure).
Multi-source data fusion techniques (e.g., optical and LIDAR) for improving satellite data quality by minimizing artifact effects (e.g., clouds, topography, reflectance anisotropy, and satellite orbit drift effects), filling data gaps, and reconstructing time-series observations.
Calibration and validation strategies for assessing the accuracy and uncertainty of remote sensing biophysical parameter products.
Long-time spatial and temporal analysis of surface biophysical products, with the underlying drivers and implications for terrestrial ecosystems process and human–nature interactions.
Original research and review articles are welcome. Review articles are suggested to cover one or more of the above topics.
Deadline for manuscript submissions: 31 July 2022.
Dr. Shengbiao Wu
Dr. Baodong Xu
Prof. Dr. Gaofei Yin
Prof. Dr. Jean-Philippe Gastellu-Etchegorry