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Physical and Environmental Geography Commons™

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Life Sciences

GSCE Faculty Publications

Series

Articles 1 - 8 of 8

Full-Text Articles in Physical and Environmental Geography

Land Surface Phenology And Seasonality Using Cool Earthlight In Croplands Of Eastern Africa And The Linkages To Crop Production, Woubet G. Alemu, Geoffrey M. Henebry Sep 2017

Land Surface Phenology And Seasonality Using Cool Earthlight In Croplands Of Eastern Africa And The Linkages To Crop Production, Woubet G. Alemu, Geoffrey M. Henebry

GSCE Faculty Publications

Across Eastern Africa, croplands cover 45 million ha. The regional economy is heavily dependent on small holder traditional rain-fed peasant agriculture (up to 90%), which is vulnerable to extreme weather events such as drought and floods that leads to food insecurity. Agricultural production in the region is moisture limited. Weather station data are scarce and access is limited, while optical satellite data are obscured by heavy clouds limiting their value to study cropland dynamics. Here, we characterized cropland dynamics in Eastern Africa for 2003–2015 using precipitation data from Tropical Rainfall Measuring Mission (TRMM) and a passive microwave dataset of land …

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A Global Analysis Of Sentinel-2a, Sentinel-2b And Landsat-8 Data Revisit Intervals And Implications For Terrestrial Monitoring, Jian Li, David P. Roy Aug 2017

A Global Analysis Of Sentinel-2a, Sentinel-2b And Landsat-8 Data Revisit Intervals And Implications For Terrestrial Monitoring, Jian Li, David P. Roy

GSCE Faculty Publications

Combination of different satellite data will provide increased opportunities for more frequent cloud-free surface observations due to variable cloud cover at the different satellite overpass times and dates. Satellite data from the polar-orbiting Landsat-8 (launched 2013), Sentinel-2A (launched 2015) and Sentinel-2B (launched 2017) sensors offer 10 m to 30 m multi-spectral global coverage. Together, they advance the virtual constellation paradigm for mid-resolution land imaging. In this study, a global analysis of Landsat-8, Sentinel-2A and Sentinel-2B metadata obtained from the committee on Earth Observation Satellite (CEOS) Visualization Environment (COVE) tool for 2016 is presented. A global equal area projection grid defined …

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Rapid Land Cover Map Updates Using Change Detection And Robust Random Forest Classifiersrapid Land Cover Map Updates Using Change Detection And Robust Random Forest Classifiers, Konrad J. Wassels, Frans Van Den Bergh, David P. Roy, Brian P. Salmon, Karen C. Steenkemp, Bryan Macalister, Derick Swanepoel, Debbie Jewitt Oct 2016

Rapid Land Cover Map Updates Using Change Detection And Robust Random Forest Classifiersrapid Land Cover Map Updates Using Change Detection And Robust Random Forest Classifiers, Konrad J. Wassels, Frans Van Den Bergh, David P. Roy, Brian P. Salmon, Karen C. Steenkemp, Bryan Macalister, Derick Swanepoel, Debbie Jewitt

GSCE Faculty Publications

The paper evaluated the Landsat Automated Land Cover Update Mapping (LALCUM) system designed to rapidly update a land cover map to a desired nominal year using a pre-existing reference land cover map. The system uses the Iteratively Reweighted Multivariate Alteration Detection (IRMAD) to identify areas of change and no change. The system then automatically generates large amounts of training samples (n > 1 million) in the no-change areas as input to an optimized Random Forest classifier. Experiments were conducted in the KwaZulu-Natal Province of South Africa using a reference land cover map from 2008, a change mask between 2008 and …

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Conterminous United States Crop Field Size Quantification From Multi-Temporal Landsat Data, Lin Yan Dr., David P. Roy Jan 2016

Conterminous United States Crop Field Size Quantification From Multi-Temporal Landsat Data, Lin Yan Dr., David P. Roy

GSCE Faculty Publications

Agricultural field size is indicative of the degree of agricultural capital investment, mechanization and labor intensity, and it is ecologically important. A recently published automated computational methodology to extract agricultural crop fields from weekly 30 m Web Enabled Landsat data (WELD) time series was refined and applied to a year of Landsat 5 Thematic Mapper (TM) and Landsat 7 Enhance Thematic Mapper Plus (ETM +) acquisitions for all of the conterminous United States (CONUS). For the first time, spatially explicit CONUS field size maps and derived information are presented. A total of 4,182,777 fields were extracted with mean and median …

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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 Mar 2013

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 …

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Prototype For Monitoring And Forecasting Fall Foliage Coloration In Real Time From Satellite Data, Xiaoyang Zhang, Mitchell D. Goldberg, Yunyue Yu Jun 2012

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 …

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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 Dec 2010

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 …

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Fire-Induced Albedo Change And Its Radative Forcing At The Surface In Northern Austrailia, Y. Jin, David P. Roy Jul 2005

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 …

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