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Unformatted text preview: Remote Sensing of Vegetation in the Sahel
ESM 266 Erin Nuccio Lana Tran Local and Regional Analysis LANDSAT NDVI 30m resolution of regions of the Sahel Burkina Faso/Mali border: 1990, 1999, 2000 Niger/Nigerian border: 1986 and 2000 AVHRR NDVI 1 km Resolution of the Sahel NDVI 1992, 1993, 1995 Desertification in the Sahel Desertification Loss of Vegetation/Productivity Soil Degradation Positive feedback Causes Drought Human Population Increases "Sahel Syndrome" Overexploitation of the Land Agriculture,deforestation Poor Irrigation Practices Possibly Climate Change
Encroachment of Saharan Dunes into Mauritania
http://pubs.usgs.gov/gip/deserts/desertification/ Desertification Occurring at a Rate of about 0.5%, ~15,500 Km2 per year Also Correlated with Rainfall Encroachment of the Saharan desert from the North Greenbelt Buffer Zone between the Sahara and the Sahel Landsat Methodology Calculate NDVI for each year Define Region of Interest Compute NDVI mean for both scenes Unable to georeference in ENVI Mean comparison Overlapping standard error bars T-test Niger/Nigerian Border
10/16/1986 10/20/2000 x = NDVI y = Pixel Frequency Mean Stdev -0.004779 0.043765 Mean Stdev 0.055402 0.082195 Mali/Burkina Faso
10/20/1990 10/29/1999 Mean Stdev -0.013664 0.058 Mean Stdev -0.002014 .06688 Rainfall Variability Trends in same direction as mean JJASO
0.15 Mean NDVI (+/- STDV) 0.1 0.05 0 -0.05 -0.1 Niger/Nigeria Mali/Burkina-Faso
1986 2000 1990 1999 Niger/Nigeria (Oct 1986, 2000); Mali/Burkina Faso (Oct 1990, 1999) Statistics T-test indicates that mean NDVI is significantly different for both scenes Paired T-test more appropriate, since scenes are not independent of each other More scenes necessary Further analysis necessary to gauge spatial annual variability Georeference, subtract bands AVHRR Lat: 9N to 16N, Long: 11W to 30E Methodology August 1-10 1992, 1993, 1995 "Band" 6: NDVI AVHRR Product Convert from 1-255 to NDVI 2 NDVI = 254 ( Pixel _ Value -1) -1 Subtract: 1992-1995, 1993-1995 Density slice Vegetation Cover Change
1992 NDVI 1995 NDVI 1993 NDVI 1995 NDVI Decrease Yellow = -0.0001 to -0.1 Orange = -0.1001 to -0.4 Red = -0.4001 to -1.2825 Increase Cyan = 0.0001 to 0.1 Green = 0.1001 to 0.2 Sea Green = 0.2 to 0.4016 Dark Blue = No Change Statistics Multiple Regression of Annual Change AVHRR and/or multiple Landsat images Independent variables Latitude, Longitude, Time Georeference datasets NDVI Directionality Precipitation Climate Change (potentially sulfate aerosols) No Directionality Land-Use Change QUESTIONS? Seasonal Variability Min Max Mean Stdev -0.45 0.721 0.0429 0.0969 Mali/Burkina Faso 8/12/00 (Wet Season) ...
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This note was uploaded on 08/06/2008 for the course ESM 266 taught by Professor Dozier during the Spring '08 term at UCSB.
- Spring '08