Abstract
The processes that determine the seasonality of precipitation in the Congo Basin are examined using the atmospheric column moisture budget. Studying the fundamental determinants of Congo Basin precipitation seasonality supports process-based studies of variations on all time scales, including those associated with greenhouse gas-induced global warming. Precipitation distributions produced by the ERA5 reanalysis provide sufficient accuracy for this analysis, which requires a consistent dataset to relate the atmospheric dynamics and moisture distribution to the precipitation field. The Northern and Southern Hemisphere regions of the Congo Basin are examined separately to avoid the misconception that Congo Basin rainfall is primarily bimodal. While evapotranspiration is indispensable for providing moisture to the atmospheric column to support precipitation in the Congo Basin, its seasonal variations are small and it does not drive precipitation seasonality. During the equinoctial seasons, precipitation is primarily supported by meridional wind convergence in the moist environment in the 800–500 hPa layer where moist air flows into the equatorial trough. Boreal fall rains are stronger than boreal spring rains in both hemispheres because low-level moisture divergence develops in boreal spring in association with the developing Saharan thermal low. The moisture convergence term also dominates the moisture budget during the summer season in both hemispheres, with meridional convergence in the 850–500 hPa layer as cross-equatorial flow interacts with the cyclonic flow about the Angola and Sahara thermal lows. Winter precipitation is low because of dry air advection from the winter hemisphere subtropical highs over the continent.
Highlights
Equatorial western and central Africa comprises the second-largest river basin on the planet, the Congo Basin, and the second-largest tropical forest
We present a basic analysis of the Congo Basin rainfall climatology with attention to regionality and seasonality, using the constraints of the column moisture budget to understand connections to regional evapotranspiration and the larger-scale atmospheric hydrodynamics
Clarifying our understanding of current and potential changes in Congo Basin climate, and the consequences for ecosystems, requires that we develop a deeper understanding of the hydrodynamic processes that support regional precipitation and determine its seasonality
Summary
Equatorial western and central Africa comprises the second-largest river basin on the planet, the Congo Basin, and the second-largest tropical forest. The Congo River Basin is nearly half the size of the continental U.S, and the region’s tropical forest is the largest contiguous tract of forest in Africa (Shapiro et al 2020). The Congo Basin precipitation climatology is often described in the literature as being bimodal, but classification studies do not agree with this characterization. Knoben et al (2019) agree with these classifications expect they identify the narrow band along the equator as bimodal using harmonic analysis of the TMPA precipitation. As is typical of tropical forest climates, the recycling of water between the evapotranspiration and precipitation fields is thought to be roughly 30% in the Congo Basin.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
