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![Page 1: Long-term drought assessment of Northern Central African continent using Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST)](https://reader030.fdocuments.us/reader030/viewer/2022032723/56649f525503460f94c75ae8/html5/thumbnails/1.jpg)
Long-term drought assessment of Northern Central African continent using Normalized
Difference Vegetation Index (NDVI) and Land Surface Temperature (LST)
Course: CSI-655Date: May 16, 2011
Taeyoung (Jason) Choi
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Outline• Motivation• Introduction
– Drought and indices– LST-NDVI combined index
• Data sets and Methodology– About MODIS– LST product– NDVI product– Methodology
• Characteristics of Regions of Interest (ROI)• Results
– NDVI Responses – LST Responses – LST-NDVI Responses
• Summary
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Motivation
• Africa continent is facing climate changes.– Drought is the main problem.
• Drought condition could be detected by remotely sensed data especially from MODIS.
• This study is focused on drought conditions from Terra MODIS collections over a decade.– In selected locations in Northern Central Africa– Near ‘Sahel’ region
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Introduction
• Drought – prolonged insufficient in reasonable water supply
beyond the range of normal human activities.• Drought monitored by metrological
precipitation record. – Data sets were not uniformly distributed in time
and space. • Remotely sensed data sets became a
promising source.
![Page 5: Long-term drought assessment of Northern Central African continent using Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST)](https://reader030.fdocuments.us/reader030/viewer/2022032723/56649f525503460f94c75ae8/html5/thumbnails/5.jpg)
Introduction
• Remotely Sensed data sets as a drought index.– Normalize Difference Vegetation Index (NDVI)
– Land Surface Temperature (LST) • from the thermal infrared signature received by
satellite sensors• widely implemented as a proxy for vegetation condition
and combined with NDVI
RNIR
RNIRNDVI
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Introduction
• Remotely Sensed data sets as a drought index.– NDVI-LST combined relationship– ‘Universal triangle’ relationship
![Page 7: Long-term drought assessment of Northern Central African continent using Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST)](https://reader030.fdocuments.us/reader030/viewer/2022032723/56649f525503460f94c75ae8/html5/thumbnails/7.jpg)
Data sets and Methodology
• About Moderate Resolution Imaging Spectroradiometer (MODIS)
Terra (EOS-AM):Launched on 12/18/99First light on 02/24/00
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Data sets and Methodology• MODIS Land Products– Vegetation indices product MOD13 (130 scenes) – LST measures land surface temperature and
emissivity (MOD11 130 scenes)
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Data sets and Methodology• Methodology– NDVI monitoring– LST monitoring– NDVI-LST relationship monitoring• Slopes and y-crossing points.
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Regions of Interest (ROI)
• ROIs are located around the border between Chad and Central Africa Republic
• Size of 2 degrees by 2 degrees
• Latitudes of 8 degrees, 10 degrees and 12 degrees with a fixed longitude of 20 degrees
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Regions of Interest (ROI)• These ROIs are perpendicular to the direction of
‘Sahel’ region.– Between Sahara desert from the north and humid forest
region.– Environmentally very sensitive.
[11] World Resources Institute (Lead Author);Leszek Bledzki (Topic Editor) "Ecosystems and Human Well-being: Desertification Synthesis: Key Questions on Desertification in the Millennium Ecosystem Assessment". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland, Retrieved April 28, 2011
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Results• NDVI and LST from 2000 to 2010
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Results• NVDI-LST responses
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• Maximum temperature drop in May from LST.
• Dry season: decreasing slope & stable Temp.
• Wet season: increasing slope & decreasing Temp.
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Summary
• 11 years of monthly MODIS NDVI and LST data sets were used to detect central Africa drought condition.
• Dry Season– Decreasing slope with stable temperature– Getting drier
• Wet Season– Increasing slope with temperature drop– Getting more humid
• More extreme events are expected in the future. • The NDVI-LST relationship provided much stable and
comprehensive information on drought conditions.
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Backup Slides
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Results (NDVI)
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Results (LST)
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Results (NDVI-LST : Slope)
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Results (NDVI-LST : Y-crossing point)