Lake Chad, located in the middle of the African Sahel belt, underwent dramatic decreases in the 1970s and 1980s leaving less than ten percent of its 1960s surface water extent as open water. In this paper, we present an extended record (dry seasons 1988-2016) of the total surface water area of the lake (including both open water and flooded vegetation) derived using Land Surface Temperature (LST) data (dry seasons 2000-2016) from the NASA Terra MODIS sensor and EUMETSAT Meteosat-based LST measurements (dry seasons 1988-2001) from an earlier study. We also examine the total surface water area for Lake Chad using radar data (dry seasons 2015-2016) from the ESA Sentinel-1a mission. For the limited number of radar data sets available to us (18 data sets), we find on average a close match between the estimates from these data and the corresponding estimates from LST, though we find spatial differences in the estimates using the two types of data. We use these spatial differences to adjust the record (dry seasons 2000-2016) from MODIS LST. Then we use the adjusted record to remove the bias of the existing LST record (dry seasons 1988-2001) derived from Meteosat measurements and combine the two records. From this composite, extended record, we plot the total surface water area of the lake for the dry seasons of 1988-1989 through 2016-2017. We find for the dry seasons of 1988-1989 to 2016-2017 that the maximum total surface water area of the lake was approximately 16,800 sq. km (February and May, 2000), the minimum total surface water area of the lake was approximately 6400 sq. km (November, 1990), and the average was approximately 12,700 sq. km. Further, we find the total surface water area of the lake to be highly variable during this period, with an average rate of increase of approximately 143 km2 per year.
|Publication status||Published - 2018 Feb 1|
Bibliographical noteFunding Information:
Acknowledgments: Support for this research was provided by NASA under its Research Opportunities in Space and Earth Sciences (ROSES)—2009 and 2013 Interdisciplinary Studies (IDS) Program (Jack Kaye, Earth Science Research Director) through the Radiation Sciences Program managed by Hal Maring. Support was also provided by the NASA Goddard Space Flight Center’s Academic Investment for Mission Success (AIMS) Program. Additionally, we appreciate the efforts of providers of the data products used for this study from various satellite sensors, particularly, MODIS on the NASA Terra satellite, C-band SAR on ESA’s Sentinel-1a satellite, and Lake Chad surface water area data from Leblanc et al., 2011 .
© 2018 by the authors.
All Science Journal Classification (ASJC) codes
- Earth and Planetary Sciences(all)