Vagner Ferreira

Hohai University · School of Earth Science and Engineering

Study Region: Africa, with its diverse climatic zones from the humid Congo Basin to the arid Sahara Desert, where groundwater is influenced by climate variability, land use, and human activities. Study Focus: The main objective is to estimate groundwater recharge across Africa from 2003 to 2023 using a novel approach that uses GRACE-derived groundw...

The study examines the impact of Ocean Tide Loading (OTL) on Interferometric Synthetic Aperture Radar (InSAR) measurements. Key findings include: (1) OTL causes long-wavelength errors in InSAR that are significant for large-scale applications. (2) OTL artifacts in interferograms increase along coastlines. (3) OTL introduces periodic signals in Sent...

The coarse spatial resolution of the Gravity Recovery and Climate Experiment (GRACE) dataset has limited its application in local water resource management and accounting. Despite efforts to improve GRACE spatial resolution, achieving high resolution downscaled grids that correspond to local hydrological behaviour and patterns is still limited. To...

Generating accurate monthly estimations of water level fluctuations in reservoirs and lakes is crucial for supporting effective water resource management and protection. The dual-satellite configuration of Sentinel-3 makes it possible to monitor water level changes with great coverage and short time intervals. However, the potential of Sentinel-3’s...

The coarse spatial resolution of the Gravity Recovery and Climate Experiment (GRACE) data has limited its application in the management of local-scale water resources. To address this limitation, we developed a new downscaling approach using predictors from regional and global hydrological models for a 15-year period (2002–2017) and tested it in th...

The GRACE and GRACE-FO satellite missions provide mass variations as a fundamentally new observation type for a broad spectrum of novel applications in Earth science disciplines, including oceanography, geophysics, hydrology, and hydrometeorology. Despite all the key findings in hydrology, the utility of GRACE-derived Terrestrial Water Storage Anom...

The two-dimensional steady-state Budyko framework, widely used to study water-energy dynamics in landscapes, primarily focused on the partitioning of precipitation into evapotranspiration (ET) and water yield. Though this framework has been extended by incorporating water storage changes into precipitation input for non-steady state conditions, the...

Global warming is emerging as an important predictor of water availability and future water supplies across the world through inducing the frequency and severity in hydrological extremes. These extremes (e.g., drought) have potential impacts on groundwater, environmental flows, as well as increase social inequalities (limited access to water by the...

In multi-frequency and multi-constellation BeiDou Navigation Satellite System (BDS), the observation type is increased, and the observation precision is inevitably different. Consequently, it is difficult to determine the variance factors of various observations. Variance component estimation can reasonably determine the weights of different types...

The availability of terrestrial water storage anomaly (TWSA) data from the Gravity Recovery and Climate Experiment (GRACE) supports many hydrological applications. Five TWSA products are operational and publicly available, including three based on mass concentration (mascon) solutions and two based on the synthesis of spherical harmonic coefficient...

A B S T R A C T Study Region: The Zambezi River Basin in southern Africa Study focus: Modelling global freshwater systems is difficult because of the complexities of climate and anthropogenic influence on hydrological systems, especially at local scales. The rapid changes in hydrological systems caused by the influence of global climate trigger c...

Total basin runoff has been estimated via satellite-hydrologic observations since 2000 due to the high maintenance cost of in situ runoff measurements and the existence of many ungauged river basins. Previous estimates of the satellite-hydrologic basin runoff have been done by simply averaging each gridded runoff within a river basin generated from...

Traditional machine learning algorithms are recently being replaced by integrated learning techniques in pattern recognitions and predictions. These updated tools (or techniques), which attempt to explore higher dimensions and uncover hidden patterns in considerably non-linear datasets are the new normal in small, medium and large dataset even in h...

Real-time precise point positioning (RT-PPP) is an effective method to retrieve precipitable water vapor (PWV), which has better timeliness compared with the European Center for Medium-Range Weather Forecasts Reanalysis (ERA5). The real-time service (RTS) required for RT-PPP broadcasted by network link may be affected by outages. The PPP-B2b servic...

Contemporary understanding of the impacts of climate change on global drought characteristics (e.g., intensities, extents) is still limited and not well understood. This knowledge is critical because projected changes in climate are expected to impact on future water availability as well as influence decisions on how water resources are allocated....

Extracting pylons from point cloud gathered by Unmanned Aerial Vehicle LiDAR systems (UAVLS) is challenging, particularly in complex environments. The difficulty arises due to the presence of nearby objects and vegetation, which are intertwined around the pylon legs and structures. In such situations, it is hard to identify pylon points from vegeta...

Satellite-based video enables potential vehicle monitoring and tracking for urban traffic management. However, due to the tiny size of moving vehicles and cluttered background, it is difficult to distinguish actual targets from random noise and pseudo-moving objects, resulting in low detection accuracy. In contrast to the currently overused deep-le...

Parameters of hydrologic models are typically calibrated using in situ runoff observations. This calibration strategy cannot be implemented when runoff observations are not available. Additionally, the high accuracy of runoff simulation does not guarantee high simulation accuracy of other hydrologic variables, such as evaporation (ET) and terrestri...

The rapid acceleration of the global water cycle caused by changes in global climate trigger complex processes that make conventional machine learning techniques limited in assessing impacts of such changes on terrestrial water storage (TWS). This study introduces an assimilated deep learning neural network to improve the modeling of TWS dynamics....

The poor horizontal reference frame in Nigeria lacks the integrity of a twenty-first century geodetic frame because the traditional techniques, which were used in developing them had limited accuracy and are now obsolete. These geodetic controls are still in use today, especially in the execution of local geodetic operations around the country. To...

Several tropical regions of the world, including West Africa are strong climatic hotspots where increase in extreme climatic events (e.g., droughts) impact water resources and hydro-ecological systems. Even though the West African Sahel has been widely studied, reports on the rainfall climatology of coastal West Africa are considerably limited. Ass...

We propose an optimization algorithm to speed up the computation of a high-frequency geoid based on the surface integral of Stokes’s formula. Stokes’s integral computes high-frequency geoid undulations from the terrestrial gravity data. The global geopotential model (GGM) provides the respective low-frequency component of the geoid solution. The co...

Study Region: Frequent drought episodes in the arid and semi-arid parts of the South African region suggest the impact of climate change and the need for a sustainable framework for groundwater level assessments. Study focus: In this study, we developed a machine learning modelling framework based on the deep belief network (DBN) to predict the ch...

The terrestrial water storage anomaly (TWSA) from the previous Gravity Recovery and Climate Experiment (GRACE) covers a relatively short period (15 years) with several missing periods. This study explores the boosted regression trees (BRT) and the artificial neural network (ANN) to reconstruct the TWSA series between 1982 and 2014 over the Yangtze...

Study region The Upper East Region, Ghana, West Africa, lies within the Volta Basin, floods annually, and contributes substantially to Ghana’s food production. Study focus We assessed precipitation (P), evapotranspiration (ET), and total water storage anomalies from GRACE (TWSA) and GLDAS-Noah (TWCA) to study the influence of the UER’s climate on...

Understanding the impacts of climate on surface water hydrology is required to predict consequences and implications on freshwater habitats, ecological assets, and wetland functions. Although the Congo basin is considered a freshwater‐rich region, largely characterized by numerous water resources after the similitude of the Amazon basin, recent acc...

Il est nécessaire de comprendre les impacts du climat sur l'hydrologie des eaux de surface pour prévoir les conséquences et les implications sur les habitats d'eau douce, les actifs écologiques et les fonctions des zones humides. Bien que le Bassin du Congo soit considéré comme une région riche en eau douce, largement caractérisée par de nombreuses...

Previous studies have shown the feasibility of point-mass modellings for deriving terrestrial water storage (TWS) from the harmonic solutions of the Gravity Recovery And Climate Experiment (GRACE) mission at regional scales (e.g., Greenland and Antarctica). However, a thorough assessment of point-mass modelling approaches at the global and river ba...

Nowadays, SAR instruments such as ESA’s Sentinel-1 constellation, ICEYE’s constellation of small and agile radar satellites, and the upcoming ALOS-4 and NASA/ISRO SAR missions provide new opportunities for near-real-time monitoring of geohazards with enhanced spatiotemporal resolution. Sequential dynamic adjustment model is regarded as an effective...

Tunnel deformation monitoring is a crucial task to evaluate tunnel stability during the metro operation period. Terrestrial Laser Scanning (TLS) can collect high density and high accuracy point cloud data in a few minutes as an innovation technique, which provides promising applications in tunnel deformation monitoring. Here, an efficient method fo...

Study region The Niger River basin (NRB) at Niamey, West Africa. Study focus Two approaches to estimate the cross-section of rivers based solely on satellite imagery (or digital elevation model, DEM) and altimetry for a large data-deficient region are proposed. These approaches are the "lateral-method" (LM), which directly provides the cross-secti...

The effective extraction and elimination of the Global Positioning System's (GPS) common mode error (CME) is of great significance to improving the signal-to-noise ratio of the coordinate time series and accurately estimating the characteristics of the crustal deformation. In this study, the principal component analysis (PCA), Karhunen–Loeve expans...

Rivers in tropical systems across the world are well known for their strong connections with floodplain wetlands. However, increased water needs and changing climate could drive water-management policy that leads to major changes in flow or surface water availability. These changes could have deleterious effects on ecological functions and ecosyste...

The Gravity Recovery and Climate Experiment (GRACE) mission makes it possible to infer the land water storage, albeit at a scale of ~300 km. Land water storage can also be inverted from the Global Navigation Satellite System (GNSS) at the cost of a dense network, which is feasible for wealthier nations. Here, the concept of a single GNSS site as a...

Risk-management solutions that increase opportunities for adaptation plans and resilience to climate change require an understanding of climate change processes, and the trickle-down effects of droughts and floods on hydrological and socio-economic systems. To guide future expectations about droughts, this study aims to assess large-scale variabili...

In the so-called point-mass modeling, surface densities are represented by point masses, providing only an approximated solution of the surface integral for the gravitational potential. Here, we propose a refinement for the point-mass modeling based on Taylor series expansion in which the zeroth-order approximation is equivalent to the point-mass s...

Few studies have used crustal displacements sensed by the Global Positioning System (GPS) to assess the terrestrial water storage (TWS), which causes loadings. Furthermore, no study has investigated the feasibility of using GPS to image TWS over South America (SA), which contains the world’s driest (Atacama Desert) and wettest (Amazon Basin) region...

Interest in region-specific assessments of droughts and the need to optimise water resources planning and allocation on a local scale via additional investments in water infrastructures is emerging as novel management initiatives to build drought resilience. In this study, a novel two-step regularization procedure that combines statistical rotation...

The poor investments in gauge measurements for hydro-climatic research in Africa has necessitated the need to investigate how decision makers can leverage on sophisticated space-borne measurements to improve knowledge on surface water hydrology that can feed directly into water accounting processes and risk assessment from extreme droughts and its...

Modelling continental freshwater dynamics is expected to be challenging in regions with considerable influence of multi-scale global climatic drivers. An assessment of the interplay between these climatic drivers (e.g. El-Niño Southern Oscillation-ENSO) that influence hydro-climatic conditions and hydrological processes is therefore required to opt...

The hydrology of the Third Pole, Asia's freshwater tower, has shown considerable sensitivity to the impacts of climate change and human interventions, which affect the headwaters of many rivers that originate therein. For example, the Yangtze River has its basin (YRB) experiencing wetness of terrestrial water storage (TWS), which rainfall seems to...

The underlying uncertainties in the prediction of freshwater evolutions in some regions can be induced by several unmitigated human actions, multi-scale climatic drivers, and dynamic physical processes. These factors have enduring hydro-ecological effects on the environments and combine to limit our understanding of large-scale hydrological process...

The Global Positioning System (GPS) permanent stations at the equatorial and southern sub-tropical hydrobelts of South America undergo the highest seasonality on the Earth due to hydrological loadings. Fortunately, there are products that account for such variations, although some of them have not been properly evaluated. For instance, global solut...

The need for ideal drought metrics to explore the impacts of climate variability drivers on drought intensity and characteristics is essential to provide support that leads to optimizing existing templates on risk mitigation in drought-prone regions. The main aim of this study therefore is to improve contemporary understanding on the evolutionary p...

Abstract There are small pieces of evidence, suggesting that South America’s hydrological cycle is changing, which impacts its water availability and, consequently, the Earth’s surface due to its elastic response to the surface mass loading/unloading. Therefore, we analyzed 3 to 15 years of vertical crustal displacements (VCDs) due to mass loadings...

Masonry structures commonly composed of a large amount of bricks or stones. Making an inventory of bricks in masonry walls is of great importance in the fields of building documentation, change detection and pattern recognition. This paper explores the problem of brick shape extraction for point cloud data with outliers as gathered by a laser scann...

A considerable number of independent case studies have shown the explicit role of rainfall and soil moisture as drivers of surface vegetation dynamics. However, the weak relationship exhibited by rainfall and soil moisture with vegetation productivity in some semi-arid and humid ecosystems of Africa due to a complex combination of social and enviro...

Few studies have used crustal displacements sensed by the Global Positioning System (GPS) to assess the terrestrial water storage (TWS), which causes loadings. Furthermore, no study has investigated the feasibility of using GPS to image TWS over South America (SA), which contains the world’s driest (Atacama Desert) and wettest (Amazon Basin) region...

Remotely sensed terrestrial water storage changes (TWSC) from the past Gravity Recovery and Climate Experiment (GRACE) mission cover a relatively short period (≈15 years). This short span presents challenges for long-term studies (e.g., drought assessment) in data-poor regions like West Africa (WA). Thus, we developed a Nonlinear Autoregressive mod...

The use of a terrestrial laser scanner is examined to measure the changes of rock slopes subject to a wave attack test. Real scenarios are simulated in a water flume facility using a wave attack experiment representing a storm of 3000 waves. The stability of two rock slopes of different steepness was evaluated under the set conditions. For quantifi...

This paper studies the effect of omission error on height system unification by analysing the contributions of the low and high spherical harmonic degree components of a local vertical datum (LVD). Previous studies have combined the satellite-only GOCE (Gravity field and steady-state Ocean Circulation Explorer) global geopotential models (GGMs) wit...

Bricks are the vital component of most masonry structures. Their maintenance is critical to the protection of masonry buildings. Terrestrial Light Detection and Ranging (TLidar) systems provide massive point cloud data in an accurate and fast way. TLidar enables us to sample and store the state of a brick surface in a practical way. This article ai...

The main aspects of the general strategy for calculating local potential values as coordinates of the International Height Reference System (IHRS) are investigated in this study. It is a part of the "Colorado empirical experiment" organized in the context of IAG/GGOS, JWG 0.1.2: Strategy for the Realization of the IHRS. Overall, such reference syst...

The knowledge of interactions between oceanic and atmospheric processes and associated influence on drought episodes is a key step toward designing robust measure that could support government and institutional measures for drought preparedness to promote region-specific drought risk-management policy solutions. This has become necessary for the Co...

Widespread environmental impacts of frequent drought episodes in Brazil have resulted in several drought-related diagnostics studies. However, the potential of many "opportunistic sensors", such as the Global Positioning System (GPS), has not yet been considered in hydrological hazard monitoring in Brazil. In this study, the response of the Earth's...

Monitoring changes in evapotranspiration (ET) is useful in the management of water resources in irrigated agricultural landscapes and in the assessment of crop stress and vegetation conditions of drought vulnerable regions. Information on the impacts of climate variability on ET dynamics is profitable in developing water management adaptation strat...

The potential of terrestrial water storage (TWS) inverted from Gravity Recovery and Climate Experiment (GRACE) measurements to investigate water variations and their response to droughts over the Volta, Niger, and Senegal Basins of West Africa was investigated. An altimetry-imagery approach was proposed to deduce the contribution of Lake Volta to T...

Hydrological hazard events such as droughts have serious impact on humanity which includes loss of life, crop failures and food shortages, health issues, mass migration, and outbreaks of vector-borne (e.g. Aedes aegypti) diseases (e.g. Zika fever). Thus, monitoring hydrological extremes is of fundamental importance. Recently, drought monitoring has...

The selection of a global geopotential model (GGM) for modeling the long-wavelength for geoid computation is imperative not only because of the plethora of GGMs available but more importantly because it influences the accuracy of a geoid model. In this study, we propose using the Gaussian averaging function for selecting an optimal GGM and degree a...

The Maule Earthquake (Mw = 8.8) of February 27, 2010 is among the strongest earthquakes that occurred in recent years throughout the world. The crustal deformation caused by this earthquake has been widely studied using GNSS, InSAR and gravity observations. However, there is currently no estimation of the possible vertical deformations produced by...

Located at the intersection of the triple junction between the Nazca, South American, and Antarctic plates, the Chilean territory is subject to active lithospheric deformations and seismicity. Taking the difference between the satellite altimetry (ALT) data that give the absolute sea level variation and the tide gauge (TG) observations that record...

After the frequent and long drought episodes of the 1980s, a plethora of case studies have shown that West Africa remains a hot spot in the continent where despite its numerous water resources, extreme rainfall variability remains a profound challenge to the availability of freshwater for agriculture and ecosystem services. In this paper, we assess...

Space-borne geodetic sensors and model-based datasets have been used to monitor groundwater changes in the Yangtze River basin (YRB). Groundwater storage variations were computed using the following datasets: • Gravity Recovery and Climate Experiment (GRACE)-derived terrestrial water storage (TWS), • Noah driven Global Land Data Assimilation System...

Brazil has recently experienced one of its worst droughts in the last 80 years, with wide-ranging consequences for water supply restrictions, energy rationing, and agricultural losses. Northeast and Southeast Brazil, which share the São Francisco River basin (SFRB), have experienced serious precipitation reduction since 2011. We used terrestrial wa...