Shusen Wang

Natural Resources Canada | NRCan · Canada Centre for Remote Sensing

Developing effective methods for estimating regional-scale surface water storage change (ΔSW) has become increasingly important for water resources studies and environmental impact assessment. Three methods for estimating monthly ΔSW are proposed in this study, of which one is based on land surface runoff and two that use water body water budgets....

The terrestrial biosphere interacts with the free atmosphere through the exchange of energy, water, and mass [...]

This study proposes a new mathematical approach to downscale monthly terrestrial water storage anomalies (TWSA) from the Gravity Recovery and Climate Experiment (GRACE) and estimates groundwater storage anomalies (GWSA) at a daily temporal resolution and a spatial resolution of 0.25° × 0.25°, simultaneously. The method combines monthly 3° GRACE gra...

The rapid conversion of tropical rainforests into monoculture plantations of rubber (Hevea brasiliensis) in Southeast Asia (SEA) necessitates understanding of rubber tree physiology under local climatic conditions. Frequent fog immersion in the montane regions of SEA may affect the water and carbon budgets of the rubber trees and the plantation eco...

The rubber tree (Hevea brasiliensis) belongs to the evergreen broadleaved species in its native ranges, but it has a concentrated leaf senescence period after it was introduced to the Asian tropics. The mechanism behind the leaf senescence is still unclear. Models for predicting leaf senescence dates of this introduced tree have been rarely explore...

Detailed knowledge of groundwater storage improves the understanding and management of water resources. Observations from Gravity Recovery and Climate Experiment (GRACE) satellites have provided data on global terrestrial-water-storage (TWS) changes since 2002. Combining GRACE-TWS and land-surface model (LSM) estimates of soil water, snow-water equ...

It is generally accepted that land use and land management practices impact climate change through sequestration of carbon in soils, but modulation of surface energy budget can also be important. Using Landsat data to characterize cropland albedos in Canada’s three prairie soil zones, this study estimates the atmospheric carbon equivalent drawdown...

Study Region Lancang River Basin (upper reaches of the Mekong River basin within China). Study Focus Complex terranes and diverse climates are a bottleneck for understanding the hydrology of rivers originating from the Tibetan Plateau. This study deals with the impact of climate change on water storage in the Lancang River Basin, which is governed...

Study region Hudson Bay Lowlands watersheds, Ontario, Canada. Study Focus The rivers in the Hudson Bay Lowlands are a major source of freshwater entering the Arctic Ocean and they also cause major floods. In recent decades, this region has been affected by major changes in hydroclimatic processes attributed to climate change and natural climate va...

Estimating terrestrial water storage (TWS) with high spatial resolution is crucial for hydrological and water resource management. Comparing to traditional in-situ data measurement, observation from space borne sensor such as Gravity Recovery and Climate Experiment (GRACE) satellites is quite effective to obtain a large-scale TWS data. However, the...

This study generated a water yield dataset for Canada for 1979–2016 by subtracting the land surface evapotranspiration (ET) and water surface evaporation (E0) from precipitation (P). The dataset was validated in Budyko space and compared with streamflow (Q) before the spatial variability and trends were analysed. Results indicate (1) uncertainties...

Terrestrial water storage (TWS) is an essential part of the global water cycle. Long-term information of observed and modeled TWS is fundamental to analyze water resources, meteorological extreme events (e.g., droughts and floods), and the climate change impacts. Over the past several decades, hydrologists have been applying physically-based hydrol...

Streamflow hydrograph analysis has long been used for separating streamflow into baseflow and surface runoff components, providing critical information for studies in hydrology, climate and water resources. Issues with established methods include the lack of physics and arbitrary choice of separation parameters, problems in identifying snowmelt run...

High spatiotemporal resolution of terrestrial total water storage plays a key role in assessing trends and availability of water resources. This study presents a two-step method for downscaling GRACE-derived total water storage anomaly (GRACE TWSA) from its original coarse spatiotemporal resolution (monthly, 3-degree spherical cap/~300 km) to a hig...

Climate change and land use management were competing explanations for vegetation dynamics in cold and semi-arid region of north-eastern Inner Mongolia, China. In order to reveal the role of human disturbance and clarify the regional climate-vegetation relationship, long-term (1982–2013) datasets of climate variables and vegetation dynamics in a fo...

Assessing the status and trend of potential evaporation (PE) is essential for investigating the climate change impact on the terrestrial water cycle. Despite recent advances, evaluating climate change impacts on PE using pan evaporation (Epan) data in cold regions is hindered by the unavailability of Epan measurements in cold seasons due to the fre...

High-resolution data of total water storage play a key role in assessing trends and availability of water resources. This study presents an iterative adjustment method based on the Self-calibration Variance-Component Model (SCVCM) for spatially downscaling GRACE-derived Total Water Storage Anomaly (GRACE TWSA) from its original coarse resolution (∼...

Streamflow hydrograph analysis has long been used for separating streamflow into baseflow and surface-runoff components, providing critical information for studies in hydrology, climate and water resources. Defects known with established methods include the lack of physics and arbitrary choice of separation parameters, problems in identifying snowm...

Long-term (1982–2013) datasets of climate variables and Normalized Difference Vegetation Index (NDVI) were collected from Climate Research Union (CRU) and GIMMS NDVI3g. By setting the NDVI values below the threshold of 0.2 as 0, NDVI_0.2 was created to eliminate the noise caused by changes of surface albedo during non-growing period. TimeSat was em...

Study region: A 10,000 km 2 area of southwestern Ontario within the Lake Erie and Lake Ontario basins of the Laurentian Great Lakes basin, Ontario, Canada, a humid northern hydrogeological setting with abundant precipitation and recharge, and a stable Paleozoic sedimentary bedrock overlain by galacial sediment forming a relatively uncompressible se...

Due to complex natural water flux processes and the ambiguous explanation of Bouchet’s complementary theory, site-level investigations on evapotranspiration (ET) and related climate variables assist in understanding the regional hydrological response to climate change. In this study, site specific empirical parameters were incorporated in the Bouch...

Accurate estimates of evapotranspiration (ET) in arid ecosystems are important for sustainable water resource management due to competing water demands between human and ecological environments. Several empirical remotely sensed ET models have been constructed and their potential for regional scale ET estimation in arid ecosystems has been demonstr...

Pronounced climate warming over the arctic‐subarctic regions has lead to profound hydrological changes including intensified river flow, but how soil frost controls aquifer discharge remains poorly understood. This study quantifies the relationship between freezing temperature and baseflow in winter. Analyses show that the traditional reservoir mod...

Due to cold and arid climate of Tibet Autonomous Region, vegetation growth is considered to be controlled by both moisture availability and warmth. In order to reveal the patterns of regional climate change and the mechanisms of climate-vegetation interactions, long term (1982–2013) datasets of climate variables and vegetation activities were colle...

Climate models predict that droughts will increase in Southeast Asia, yet little is known about how soil respiration (Rs) and its components heterotrophic respiration (Rh) and autotrophic respiration (Ra) will change following drought years. To clarify this issue and to detect underlying mechanisms, we conducted a 2-year field experiment in the sev...

Evapotranspiration (ET) plays an important role in determining the available water resources of a basin. In past decades, the Heihe River basin (HRB) in Northwest China has suffered severe water crisis and ecological problems due to large land cover changes (LCCs), especially oases expansion for irrigation agriculture. This study quantifies the ET...

A multiple sensor payload for a multi-rotor based UAV platform was developed and tested for measuring land surface albedo and spectral measurements at user-defined spatial, temporal, and spectral resolutions. The system includes a Matrice 600 UAV with an RGB camera and a set of four downward pointing radiation sensors including a pyranometer, quant...

The widespread increase in the number of digital cameras mounted on flux towers provides an opportunity to better understand the relationship between the seasonality of canopy photosynthesis and canopy phenology. The challenge is due to fewer variations in rubber defoliation of rubber canopy. We examined the relationship between colour indices calc...

A model for downscaling SMOS soil moisture using C-band Sentinel-1/SAR data is developed. The model uses Water-Cloud model to minimize the effect of vegetation on soil moisture retrieval. The model uses the wavelet transform to account for spatial heterogeneity varying between scales

The water cloud model (WCM) is a widely used radar backscatter model applied to SAR images to retrieve soil moisture over vegetated areas. The WCM needs vegetation descriptors to account for the impact of vegetation on SAR backscatter. The commonly used vegetation descriptors in WCM, such as Leaf Area Index (LAI) and Normalized Difference Vegetatio...

The distribution of forest vegetation and forest carbon sequestration potential are significantly influenced by climate change. In this study, a map of the current distribution of vegetation in Yunnan Province was compiled based on data from remote sensing imagery from the Advanced Land Observing Satellite (ALOS) from 2008 to 2011. A classification...

Snow and ice over land are important hydrological resources and sensitive indicators of climate change. The Moderate Resolution Imaging Spectroradiometer (MODIS) dataset at 250-m spatial resolution generated at the Canada Centre for Remote Sensing (CCRS) is used to derive the annual minimum snow and ice (MSI) extent over the Canadian Arctic landmas...

A new method was developed in this study for producing a clear-sky Landsat composite for cropland from cloud-contaminated Landsat images acquired in a short time period. It used Thiel–Sen regression to normalize all Landsat scenes to a MODIS image to make all Landsat images radiometrically consistent and comparable. Pixel selection criteria combini...

Seasonal water temperature data from 388 large Canadian lakes (area ≥ 100 km²) were used to develop improved empirical tools for forecasting the impacts of climate change on the magnitude (TP) and time of occurrence (JP) of annual peak surface water temperatures. Analyses of remotely sensed open-water temperatures with sinusoidal models produced es...

Flooding is projected to increase with climate change in many parts of the world. Floods in cold regions are commonly a result of snowmelt during the spring break-up. The peak river flow (Qpeak) for the Mackenzie River, located in northwest Canada, is modelled using the Gravity Recovery and Climate Experiment (GRACE) satellite observations. Compare...

Canopy conductance (gc) is an important factor influencing plant transpiration and photosynthesis, and it is sensitive to environmental factors. Evapotranspiration and environmental factors of a shrub ecosystem, which was dominated by Artemisia ordosica in northwestern China, were continuously measured using eddy covariance technique in growing sea...

Accurately mapping crop area using coarse spatial resolution remote sensing imageries is challenging due to the existence of various spatial heterogeneities. The objective of this study is to analyze the accuracy of crop classification and area estimation affected by spatial heterogeneities, especially for sample impurity and landscape heterogeneit...

Quantifying terrestrial water storage (TWS) and its dynamic changes has been a key subject in water-related research and resources management. The Gravity Recovery and Climate Experiment (GRACE) satellite mission has been providing opportunities to observe monthly TWS since 2002. This study characterizes the TWS climatology over Canada, using GRACE...

Flood forecasting of the spring freshet for cold-region watersheds where the discharge is predominately governed by snowpack accumulation and melting remains a challenge. A cold-region flood forecasting model is developed, using data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. The model forecasts flood by simulating...

Principal component analysis (PCA) is a statistical technique widely used in remote sensing, yet few studies have addressed the physical meaning of component images. Using PCA, this study analyzed the long-term (2003–2013) monthly terrestrial water storage (TWS) over Canada time series dataset from the Gravity Recovery and Climate Experiment (GRACE...

Snow and ice are important hydrological resources. Their minimum spatial extent over land, here referred to as annual minimum snow/ice (MSI) cover, plays a very important role as an indicator of long-term changes and baseline capacity for surface water storage. Data from Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra satellite for t...

The peak river flow for the Mackenzie River is modelled using GRACE satellite observations and temperature data, which advances the applications of space-based time-variable gravity measurements in cold region flood forecasting. The model estimates peak river flow by simulating peak surface runoff from snowmelt and the corresponding baseflow. The m...

Developing the ability to seamlessly predict streamflow and other state variables at catchment, regional, continental or global scales with spatial resolutions varying from hundreds to thousands of meters is fundamental for improving our understanding of the water balance at scales relevant for decision making as well as for improving our understan...

Ecosystem responses to rising CO 2 concentrations are a major source of uncertainty in climate change projections. Data from ecosystem-scale Free-Air CO 2 Enrichment (FACE) experiments provide a unique opportunity to reduce this uncertainty. The recent FACE Model-Data Synthesis project aimed to use the information gathered in two forest FACE experi...

This study compares six evapotranspiration (ET) products for Canada’s landmass, viz., eddy covariance (EC) measurements, surface water budget ET, remote sensing ET from MODIS, and land surface model (LSM) ET from the Community Land Model (CLM), the Ecological Assimilation of Land and Climate Observations (EALCO) model, and the Variable Infiltration...

The use of synthetic aperture radar (SAR) imagery is generally considered to be an effective method for detecting surface water. Among various supervised/unsupervised classification methods, a SAR-intensity-based histogram thresholding method is widely used to distinguish waterbodies from land. A SAR texture-based automatic thresholding method is p...

The target or polarimetric decomposition is widely used to process multi-polarization SAR imagery to establish a correspondence between physical characteristics of interested objects and observed scattering mechanisms. Polarimetric decomposition parameters are used as the basis for developing new classification methods for analyzing polarimetric SA...

Climate and land cover changes impact groundwater resources primarily through changes in net surface recharge. Actual evapotranspiration and the partitioning between runoff and groundwater infiltration govern the rate of aquifer recharge. Remote sensing technology opens up new possibilities for groundwater recharge modeling through a rapid method o...

This study assessed the long-term (1979-2008) water budget closures for 19 large cold region drainage basins in Canada using recently developed datasets for precipitation (P), land surface evapotranspiration and water surface evaporation, and observed streamflow. Total water storage (TWS) trends from the GRACE satellite observations were also used...

Estimating the recharge rate in a country as large as Canada is challenging but crucial for sustainable water development. In this presentation, we show a proof-of-concept methodology to illustrate the estimation of groundwater recharge for the whole landmass of Canada, using regional water budgets based on monthly GRACE terrestrial water storage e...

This study examined the long-term water budget closures for 370 watersheds over Canada's landmass by using 30 years’ (1981-2010) data products recently produced for precipitation (P) gridded using climate station measurements, land surface evapotranspiration (ET) and water surface evaporation (E0) obtained by the EALCO model, and observed streamflo...

Elevated atmospheric CO 2 concentration ( eCO 2 ) has the potential to increase vegetation carbon storage if increased net primary production causes increased long‐lived biomass. Model predictions of eCO 2 effects on vegetation carbon storage depend on how allocation and turnover processes are represented. We used data from two temperate forest fre...

Modelled labile carbohydrate store at Duke and at Oak Ridge. Notes S1 Carbohydrate storage and remobilisation. Notes S2Differences among model predictions of allocation patterns at ambient CO2 concentration.

Free Air CO2 Enrichment (FACE) experiments provide a remarkable wealth of data which can be used to evaluate and improve terrestrial ecosystem models (TEMs). In the FACE Model-Data Synthesis project (FACE-MDS), 11 TEMs were applied to two decade-long FACE experiments in temperate forests of the south eastern US—the evergreen Duke Forest and the dec...

Using data from 13 climate stations on the Canadian Prairies, together with opaque cloud cover and daily snow depth, to analyze the winter climate transitions with snow, we find that a snow cover acts as a fast climate switch. Surface temperature falls by about 10K with fresh snowfall and rises by a similar amount with snowmelt, while the daily ran...

We analysed the responses of 11 ecosystem models to elevated atmospheric [CO2] (eCO2) at two temperate forest ecosystems (Duke and Oak Ridge National Laboratory (ORNL) Free-Air CO2 Enrichment (FACE) experiments) to test alternative representations of carbon (C)–nitrogen (N) cycle processes. We decomposed the model responses into component processe...

Fig. S1 Cumulative effect of elevated atmospheric [CO2] (eCO2) on carbon (C) and nitrogen (N) storage in the Duke and Oak Ridge National Laboratory (ORNL) Free-Air CO2 Enrichment (FACE) sites.

A 30 yr (1979–2008) dataset of actual evapotranspiration (ET) at 1 km resolution was generated over Canada's landmass by integrating remote sensing land surface data and gridded climate data using the EALCO model run at a 30 min time step. This long-term high-resolution dataset was used to characterize the spatiotemporal variations in ET across Can...

A 30 yr (1979-2008) dataset of actual evapotranspiration (ET) at 1 km resolution was generated over Canada's landmass by integrating remote sensing land surface data and gridded climate data using the EALCO model run at 30 min time step. This long-term high resolution dataset was used to characterize the spatiotemporal variations in ET across Canad...

Canada's territory holds 10% of the world's forest, mostly in high-latitude areas with a dominance of conifers and with snowy winters. Changes in disturbance regimes and in climate may change both the extent and duration of the snow cover as well as the type and properties of the forest cover, thereby providing either negative or positive feedback...