Spatiotemporal variability of droughts in the Congo River Basin: The
role of atmospheric moisture transport
Abstract
The spatiotemporal evolution of droughts in the Congo River Basin (CRB)
from 1981–2018 was investigated using the Standardised Precipitation
Index (SPI) and Standardised Precipitation–Evapotranspiration Index
(SPEI) to assess the roles of precipitation and potential
evapotranspiration. The results confirmed a notable trend toward drier
conditions, particularly in parts of the northern and central basin, as
well as in the south of the CRB, which was associated with increases in
potential evapotranspiration and declining rainfall. Global outputs of
the Lagrangian model FLEXPART were used to model air masses over four
important climatological regions considered to be the main sources of
precipitation in the CRB, and their contributions to precipitation over
the basin were computed. These analyses confirmed that moisture in the
CRB is ~60% self-sourced; African lands were the next
greatest contributor, followed by the Indian and Atlantic Oceans. It was
found that a reduction in contributions of the sources prevailed during
53 meteorological drought episodes that affected the CRB during the
study period and it could be inferred that a reduction in moisture
supplied from the Atlantic and Indian Oceans played an important role in
the onset of drought episodes. It was also observed that the
contribution of moisture from all sources to the CRB decreased during
the study period, especially over the northern half of the basin, where
the main humid forest of the CRB is located, confirming the importance
of water transport and local hydroclimatological dynamics on the
hydrological conditions, ecosystems, and local communities of the CRB.