Evapotranspiration Variability and Its Association with Vegetation Dynamics in the Nile Basin, 2002-2011

被引:34
作者
Alemu, Henok [1 ]
Senay, Gabriel B. [1 ,2 ]
Kaptue, Armel T. [1 ]
Kovalskyy, Valeriy [1 ]
机构
[1] S Dakota State Univ, GSCE, Brookings, SD 57007 USA
[2] US Geol Survey, Earth Resources Observat & Sci EROS Ctr, Sioux Falls, SD 57198 USA
关键词
evapotranspiration; vegetation productivity; NDVI; land cover; climate; rainfall; trend analysis; Nile Basin; MAPPING DAILY EVAPOTRANSPIRATION; ENERGY-BALANCE; WATER-BALANCE; MODIS; EVAPORATION; PRODUCTS; HIGHLANDS; IMAGERY; TRENDS; FLUXES;
D O I
10.3390/rs6075885
中图分类号
X [环境科学、安全科学];
学科分类号
08 ; 0830 ;
摘要
Evapotranspiration (ET) is a vital component in land-atmosphere interactions. In drylands, over 90% of annual rainfall evaporates. The Nile Basin in Africa is about 42% dryland in a region experiencing rapid population growth and development. The relationship of ET with climate, vegetation and land cover in the basin during 2002-2011 is analyzed using thermal-based Simplified Surface Energy Balance Operational (SSEBop) ET, Normalized Difference Vegetation Index (NDVI)-based MODIS Terrestrial (MOD16) ET, MODIS-derived NDVI as a proxy for vegetation productivity and rainfall from Tropical Rainfall Measuring Mission (TRMM). Interannual variability and trends are analyzed using established statistical methods. Analysis based on thermal-based ET revealed that >50% of the study area exhibited negative ET anomalies for 7 years (2009, driest), while >60% exhibited positive ET anomalies for 3 years (2007, wettest). NDVI-based monthly ET correlated strongly (r > 0.77) with vegetation than thermal-based ET (0.52 < r < 0.73) at p < 0.001. Climate-zone averaged thermal-based ET anomalies positively correlated (r = 0.6, p < 0.05) with rainfall in 4 of the 9 investigated climate zones. Thermal-based and NDVI-based ET estimates revealed minor discrepancies over rainfed croplands (60 mm/yr higher for thermal-based ET), but a significant divergence over wetlands (440 mm/yr higher for thermal-based ET). Only 5% of the study area exhibited statistically significant trends in ET.
引用
收藏
页码:5885 / 5908
页数:24
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