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Articles 31 - 41 of 41
Full-Text Articles in Physical and Environmental Geography
A One Year Landsat 8 Conterminous United States Study Of Cirrus And Non-Cirrus Clouds, Valeriy Kovalskyy, David P. Roy
A One Year Landsat 8 Conterminous United States Study Of Cirrus And Non-Cirrus Clouds, Valeriy Kovalskyy, David P. Roy
GSCE Faculty Publications
The first year of available Landsat 8 data over the conterminous United States (CONUS), composed of 11,296 acquisitions sensed over more than 11 thousand million 30 m pixel locations, was analyzed comparing the spatial and temporal incidence of 30 m cloud and cirrus states available in the standard Landsat 8 Level 1 product suite. This comprehensive data analysis revealed that on average over a year of CONUS observations (i) 35.9% were detected with high confidence cloud, with spatio-temporal patterns similar to those observed by previous Landsat 5 and 7 cloud analyses; (ii) 28.2% were high confidence cirrus; (iii) 20.1% were …
A Cross Comparison Of Spatiotemporally Enhanced Springtime Phenological Measurements From Satellites And Ground In A Northern U.S. Mixed Forest, Liang Liang, Mark D. Schwartz, Zhuosen Wang, Feng Gao, Crystal B. Schaaf, Bin Tan, Jeffrey T. Morisette, Xiaoyang Zhang
A Cross Comparison Of Spatiotemporally Enhanced Springtime Phenological Measurements From Satellites And Ground In A Northern U.S. Mixed Forest, Liang Liang, Mark D. Schwartz, Zhuosen Wang, Feng Gao, Crystal B. Schaaf, Bin Tan, Jeffrey T. Morisette, Xiaoyang Zhang
GSCE Faculty Publications
Cross comparison of satellite-derived land surface phenology (LSP) and ground measurements is useful to ensure the relevance of detected seasonal vegetation change to the underlying biophysical processes. While standard 16-day and 250-m Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation index (VI)-based springtime LSP has been evaluated in previous studies, it remains unclear whether LSP with enhanced temporal and spatial resolutions can capture additional details of ground phenology. In this paper, we compared LSP derived from 500-m daily MODIS and 30-m MODIS-Landsat fused VI data with landscape phenology (LP) in a northern U.S. mixed forest. LP was previously developed from intensively observed …
Interannual Variations And Trends In Global Land Surface Phenology Derived From Enhanced Vegetation Index During 1982–2010, Xiaoyang Zhang, Bin Tan, Yunyue Yu
Interannual Variations And Trends In Global Land Surface Phenology Derived From Enhanced Vegetation Index During 1982–2010, Xiaoyang Zhang, Bin Tan, Yunyue Yu
GSCE Faculty Publications
Land surface phenology is widely retrieved from satellite observations at regional and global scales, and its long-term record has been demonstrated to be a valuable tool for reconstructing past climate variations, monitoring the dynamics of terrestrial ecosystems in response to climate impacts, and predicting biological responses to future climate scenarios. This study detected global land surface phenology from the advanced very high resolution radiometer (AVHRR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) data from 1982 to 2010. Based on daily enhanced vegetation index at a spatial resolution of 0.05 degrees, we simulated the seasonal vegetative trajectory for each individual pixel …
The Global Availability Of Landsat 5 Tm And Landsat 7 Etm+ Land Surface Observations And Implications For Global 30m Landsat Data Product Generation, V. Kovalskyy, David P. Roy
The Global Availability Of Landsat 5 Tm And Landsat 7 Etm+ Land Surface Observations And Implications For Global 30m Landsat Data Product Generation, V. Kovalskyy, David P. Roy
GSCE Faculty Publications
With the advent of the free U.S. Landsat data policy it is now feasible to consider the generation of global coverage 30 m Landsat data sets with temporal reporting frequency similar to that provided by the monthly Web Enabled Landsat (WELD) products. A statistical Landsat metadata analysis is reported considering more than 800,000 Landsat 5 TM and Landsat 7 ETM + acquisitions obtained from the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center archive. The global monthly probabilities of acquiring a cloud-free land surface observation for December 1998 to November 2001 (2000 epoch) and from December 2008 …
Daily Modis 500 M Reflectance Anisotropy Direct Broadcast (Db) Products For Monitoring Vegetation Phenology Dynamics, Yanmin Shuai, Crystal Schaaf, Xiaoyang Zhang, Alan Strahler, David P. Roy, Jeffery Morisette, Zhuosen Wang, Joanne Nightingale, Jaime Nickerson, Andrew D. Richardson, Donghui Xie, Jindi Wang, Xiaowen Li, Kathleen Strabala, James E. Davies
Daily Modis 500 M Reflectance Anisotropy Direct Broadcast (Db) Products For Monitoring Vegetation Phenology Dynamics, Yanmin Shuai, Crystal Schaaf, Xiaoyang Zhang, Alan Strahler, David P. Roy, Jeffery Morisette, Zhuosen Wang, Joanne Nightingale, Jaime Nickerson, Andrew D. Richardson, Donghui Xie, Jindi Wang, Xiaowen Li, Kathleen Strabala, James E. Davies
GSCE Faculty Publications
Land surface vegetation phenology is an efficient bio-indicator for monitoring ecosystem variation in response to changes in climatic factors. The primary objective of the current article is to examine the utility of the daily MODIS 500 m reflectance anisotropy direct broadcast (DB) product for monitoring the evolution of vegetation phenological trends over selected crop, orchard, and forest regions. Although numerous model-fitted satellite data have been widely used to assess the spatio-temporal distribution of land surface phenological patterns to understand phenological process and phenomena, current efforts to investigate the details of phenological trends, especially for natural phenological variations that occur on …
Prototype For Monitoring And Forecasting Fall Foliage Coloration In Real Time From Satellite Data, Xiaoyang Zhang, Mitchell D. Goldberg, Yunyue Yu
Prototype For Monitoring And Forecasting Fall Foliage Coloration In Real Time From Satellite Data, Xiaoyang Zhang, Mitchell D. Goldberg, Yunyue Yu
GSCE Faculty Publications
While determining vegetation phenology from the time series of historical satellite data has been widely investigated throughout the last decade, little effort has been devoted to real-time monitoring and short-term forecasting. The latter is more important for numerical weather modeling, ecosystem forecasting, forest and crop management, and health risk warning. In this study we developed a prototype approach for the real-time monitoring and short-term forecasting of fall foliage status (including low coloration, moderate coloration, near-peak coloration, peak coloration, and post-peak coloration) using temporal satellite observations. The algorithm combined the climatology of vegetation phenology and temporally available satellite observations to establish …
Sensitivity Analysis Of The Gems Soil Organic Carbon Model To Land Cover Land Use Classification Uncertainties Under Different Climate Scenarios In Senegal, Amadou M. Dieye, David P. Roy, N. P. Hanan, S. Lui, M. Hansen, A. Toure
Sensitivity Analysis Of The Gems Soil Organic Carbon Model To Land Cover Land Use Classification Uncertainties Under Different Climate Scenarios In Senegal, Amadou M. Dieye, David P. Roy, N. P. Hanan, S. Lui, M. Hansen, A. Toure
GSCE Faculty Publications
Spatially explicit land cover land use (LCLU) change information is needed to drive biogeochemical models that simulate soil organic carbon (SOC) dynamics. Such information is increasingly being mapped using remotely sensed satellite data with classification schemes and uncertainties constrained by the sensing system, classification algorithms and land cover schemes. In this study, automated LCLU classification of multi-temporal Landsat satellite data were used to assess the sensitivity of SOC modeled by the Global Ensemble Biogeochemical Modeling System (GEMS). The GEMS was run for an area of 1560km2 in Senegal under three climate change scenarios with LCLU maps generated using different Landsat …
Exploiting The Power Law Distribution Properties Of Satellite Fire Redaiative Power Retrials: A Method To Estimate Fire Radiative Energy And Biomass Burned From Sparse Satellite Observations, S. S. Kumar, David P. Roy, L. Boschetti, R. Kremens
Exploiting The Power Law Distribution Properties Of Satellite Fire Redaiative Power Retrials: A Method To Estimate Fire Radiative Energy And Biomass Burned From Sparse Satellite Observations, S. S. Kumar, David P. Roy, L. Boschetti, R. Kremens
GSCE Faculty Publications
Instantaneous estimates of the power released by fire (fire radiative power, FRP) are available with satellite active fire detection products. The temporal integral of FRP provides an estimate of the fire radiative energy (FRE) that is related linearly to the amount of biomass burned needed by the atmospheric emissions modeling community. The FRE, however, is sensitive to satellite temporal and spatial FRP undersampling due to infrequent satellite overpasses, cloud and smoke obscuration, and failure to detect cool and/or small fires. Satellite FRPs derived over individual burned areas and fires have been observed to exhibit power law distributions. This property is …
Radiative Forcing Over The Conterminous United States Due To Contemporary Land Cover Use Change And Sensitivity To Snow And Interannual Albedo Variability, Christoper A. Barnes, David P. Roy
Radiative Forcing Over The Conterminous United States Due To Contemporary Land Cover Use Change And Sensitivity To Snow And Interannual Albedo Variability, Christoper A. Barnes, David P. Roy
GSCE Faculty Publications
Satellite‐derived land cover land use (LCLU), snow and albedo data, and incoming surface solar radiation reanalysis data were used to study the impact of LCLU change from 1973 to 2000 on surface albedo and radiative forcing for 58 ecoregions covering 69% of the conterminous United States. A net positive surface radiative forcing (i.e., warming) of 0.029 Wm−2 due to LCLU albedo change from 1973 to 2000 was estimated. The forcings for individual ecoregions were similar in magnitude to current global forcing estimates, with the most negative forcing (as low as −0.367 Wm−2) due to the transition to forest and the …
Large Seasonal Swings In Leaf Area Of Amazon Rainforests, Ranga B. Myneni, Wenze Yang, Ramakrishna R. Nemani, Alfredo R. Huete, Robert E. Dickinson, Yuri Knyazikhin, Kamel Didan, Rong Fu, Robinson I. Negron Juarez, Sasan S. Saatchi, Hirofumi Hashimoto, Kazuhito Ichii, Nikolay V. Shabanov, Bin Tan, Piyachat Ratana, Jeffrey L. Privette, Jeffrey T. Morisette, Eric F. Vermote, David P. Roy, Robert E. Wolfe, Mark A. Friedl, Steven W. Running, Petr Votava, Nazmi El-Saleous, Sadashiva Devadiga, Yin Su, Vincent V. Salomonson
Large Seasonal Swings In Leaf Area Of Amazon Rainforests, Ranga B. Myneni, Wenze Yang, Ramakrishna R. Nemani, Alfredo R. Huete, Robert E. Dickinson, Yuri Knyazikhin, Kamel Didan, Rong Fu, Robinson I. Negron Juarez, Sasan S. Saatchi, Hirofumi Hashimoto, Kazuhito Ichii, Nikolay V. Shabanov, Bin Tan, Piyachat Ratana, Jeffrey L. Privette, Jeffrey T. Morisette, Eric F. Vermote, David P. Roy, Robert E. Wolfe, Mark A. Friedl, Steven W. Running, Petr Votava, Nazmi El-Saleous, Sadashiva Devadiga, Yin Su, Vincent V. Salomonson
GSCE Faculty Publications
Despite early speculation to the contrary, all tropical forests studied to date display seasonal variations in the presence of new leaves, flowers, and fruits. Past studies were focused on the timing of phenological events and their cues but not on the accompanying changes in leaf area that regulate vegetation–atmosphere exchanges of energy, momentum, and mass. Here we report, from analysis of 5 years of recent satellite data, seasonal swings in green leaf area of ~25% in a majority of the Amazon rainforests. This seasonal cycle is timed to the seasonality of solar radiation in a manner that is suggestive of …
Fire-Induced Albedo Change And Its Radative Forcing At The Surface In Northern Austrailia, Y. Jin, David P. Roy
Fire-Induced Albedo Change And Its Radative Forcing At The Surface In Northern Austrailia, Y. Jin, David P. Roy
GSCE Faculty Publications
This paper investigates the impact of fire on surface albedo and the associated radiative forcing over 56% of continental Australia encompassing the fire-prone northern tropical savanna. Fire-affected areas and albedos are derived for the 2003 fire season using daily Moderate Resolution Imaging Spectroradiometer (MODIS) surface reflectance data. Near-infrared and total shortwave albedos are observed to generally decrease after fire occurrence. Regionally, the total shortwave albedo drops by an average of 0.024, with increasing reductions as the dry season progresses and larger reductions in grasslands than woody savannas. These fire-induced albedo changes exert a positive forcing at the surface that increases …