干旱区生态环境知识资源中心

This work assesses the connections between satellite-derived vegetation activity and Outgoing Longwave Radiation (OLR) over West African Sahel as a diagnostic of land-atmosphere feedbacks of relevance to environmental change. A regional analysis of 20 years of land-atmosphere interactions were completed and were based on the Normalized Difference Vegetation Index (NDVI) derived from the National Oceanographic and Atmospheric Administration's (NOAA) Advanced Very High Resolution Radiometer (AVHRR) sensor for the Pathfinder AVHRR Land (PAL) program and OLR data over 1982-2001. The minimum. mean, maximum and Coefficient of Variation (CV) analyses of the NDVI and OLR data were applied to assess seasonal responses to environmental change. The results indicated a significant positive correlation [r(2) = +0.74, p=0.005] between the CV of NDVI and OLR. Other important finding was the large CV value of OLR in March over West Sahel Africa, with a mean CV of 20%, which may he related to the atmospheric dust. from the Sahara desert region. Overall, the relationships between NDVI and OLR in drylands are much more complex and less well understood than initially assumed, with major uncertainties revolving around the atmospheric dust.