1. Long-term drought assessment of Northern Central African continent using Normalized Difference Vegetation Index (NDVI) and Land Surface Temperature (LST) Course: CSI-655 Date: May 16, 2011 Taeyoung (Jason) Choi

2. 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

3. 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

4. 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.

5. 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

6. Introduction Remotely Sensed data sets as a drought index. – NDVI-LST combined relationship – ‘Universal triangle’ relationship

7. Data sets and Methodology About Moderate Resolution Imaging Spectroradiometer (MODIS) Terra (EOS-AM): Launched on 12/18/99 First light on 02/24/00

8. Data sets and Methodology MODIS Land Products – Vegetation indices product MOD13 (130 scenes) – LST measures land surface temperature and emissivity (MOD11 130 scenes)

9. Data sets and Methodology Methodology – NDVI monitoring – LST monitoring – NDVI-LST relationship monitoring Slopes and y-crossing points.

10. 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

11. 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

12. Results NDVI and LST from 2000 to 2010

13. Results NVDI-LST responses

14. Maximum temperature drop in May from LST. Dry season: decreasing slope & stable Temp. Wet season: increasing slope & decreasing Temp.

15. 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.

16. Backup Slides

17. Results (NDVI)

18. Results (LST)

19. Results (NDVI-LST : Slope)

20. Results (NDVI-LST : Y-crossing point)