Relationships between NDVI, river discharge and climate in the Okavango River Basin region. (4th July 2021)

• Record Type: Journal Article
• Authors: Moses, Oliver; Blamey, Ross C.; Reason, Chris J. C.
• Is Part Of: International journal of climatology. Volume 42:Number 2(2022)
• Page Start: 691
• Page End: 713
• Publication Date: 2021-07-04
• Subjects: climate variability -- NDVI -- river discharge -- southern Africa -- trends; Climatology -- Periodicals; Climat -- Périodiques; Climatologie -- Périodiques; 551.605
• DOI: 10.1002/joc.7267
• Languages: English
• ISSNs: 0899-8418

Abstract

Abstract: The Okavango River Basin (ORB) is a highly sensitive and biodiverse region in southern Africa whose climate, vegetation and river discharge characteristics are not well understood. This study investigated relationships between rainfall, temperature, Normalized Difference Vegetation Index (NDVI) and river discharge over the region as well as their trends and interannual variability. It is found that spatial patterns of NDVI are closely related to those of rainfall, but less so with temperature at monthly and seasonal time scales. The relationships between NDVI and rainfall/temperature differ north of 18.9°S where rainfall is higher than to its south. Typically, there are lags of 1–2‐months between NDVI and either rainfall or temperature. Also, there are large areas across the region that show significant warming trends in all seasons as well as wetting (mainly in the north). This increasing trend in surface temperature may act to worsen the impacts of extreme events such as severe drought and fire in the region. There is also pronounced interannual variability with significant correlations found with El Niño‐Southern Oscillation (ENSO), the subtropical South Indian Ocean Dipole and the Botswana High for rainfall and temperature, and for NDVI with ENSO. For the Southern Annular Mode, significant correlations were found with rainfall and temperature only in December and April. On longer time scales, focus was also placed on the wet 2006–2013 period relative to much drier 1999–2005 epoch for October–December. The wetter conditions during 2006–2013 appear related to La Niña Modoki conditions and warmer sea surface temperature near Angola as well as regional circulation differences. Abstract : The Okavango River Basin is a highly sensitive and biodiverse region in southern Africa which includes the World Heritage Site Okavango Delta. Significant trends in rainfall, NDVI and temperature are found over many parts of the region during the summer rainy season. There is also pronounced interannual variability in the regional climate, some of which is related to ENSO and the Botswana High.