Central African Climate

Pokam, Wilfried M.; Vondou, Derbetini A.; Kamsu‐Tamo, Pierre Honore

doi:10.1002/9781119657002.ch2

Cited by 5 publications

(4 citation statements)

References 69 publications

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“…It is suggested that an appraisal of the variability in rain cells propagation and properties would help explain the intra‐seasonal to seasonal rainfall variations over Central Africa, which remain poorly understood (Dezfuli, 2017; Pokam Mba et al, 2022). In view of the human‐induced ongoing warming of the global atmosphere, which affects water vapour content and convective activity, we also recommend monitoring future changes in rain cell characteristics which are strong determinants of the local frequency and intensity of rain events.…”

Section: Discussionmentioning

confidence: 99%

“…Central Africa has been off the radar of climatological research for many years, and the mechanisms of rainfall variability in the region are still poorly understood (Dezfuli, 2017; Nicholson, 2022). While significant advances have been made in the description and understanding of West African rainfall disturbances (Lafore et al, 2011; Parker & Diop‐Kane, 2017), much less is known about those of Central Africa (Pokam Mba et al, 2022). Early studies were carried out by French tropical meteorologists in the 1950s, based on synoptic and upper‐air observations.…”

Section: Introductionmentioning

confidence: 99%

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Seasonal variations in rain cells propagation over Central Africa and association with diurnal rainfall regimes

Camberlin,

Moron,

Philippon

et al. 2024

Intl Journal of Climatology

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Three‐hourly data from two satellite rainfall estimates products, PERSIANN and TMPA, are analysed to document the seasonal patterns of diurnal rainfall distribution over the Congo Basin and neighbouring areas. PERSIANN data for 2001–2017, at a one‐hour time‐scale, are further used to identify rain cells (≥4 mm·h−1) in an attempt to explain the diurnal rainfall variations. Over land areas, an afternoon rainfall maximum is clearly shown, but over much of the region only a minor part of the rains (20%–30%) falls in the wettest 3‐h period. Substantial rains (often 50%–60%) occur in the evening and at night, as a progressively delayed peak from east to west, but a seasonal change is found in the meridional propagation of the peak diurnal rainfall, in a south‐westerly direction in January, and a north‐westerly direction in July. Rain cells have prominent genesis areas west of high terrain, but can develop over most regions, with a peak genesis time slightly ahead the diurnal phase of the rains. The size, mean lifetime and mean rainfall intensity of the rain cells are strongly related to each other and display a semi‐annual cycle not fully in phase with the seasonal cycle of the rains. The mean rain cell propagation speed (6.7 m·s−1) is much lower than in previous studies, which focused on mesoscale convective systems. Rain cells which have a longer lifetime move much faster, the mean speed of those lasting less than 6 h being half that of those lasting at least 24 h. Most (86%) of the mobile rain cells propagate westward, but the meridional component of their propagation shows an annual cycle (southward in austral summer, northward in boreal summer) which matches the mid‐tropospheric winds and explains the seasonal changes in the diurnal rainfall peak.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seasonal variations in rain cells propagation over Central Africa and association with diurnal rainfall regimes

Camberlin,

Moron,

Philippon

et al. 2024

Intl Journal of Climatology

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“…It is likely that the role these systems play in controlling rainfall differs between the northern and southern parts of the hemisphere, especially as most recent studies conclude that a biannual rainfall regime exists along the equatorial band, with an annual regime surrounding it (e.g., Cook and Vizy 2022, Nicholson 2022, Mba et al, 2022. The annual versus biannual rainfall regime highly depends on the area chosen for rainfall (e.g., Dezfuli, 2017).…”

Section: Introductionmentioning

confidence: 99%

On the Mechanisms that Control the Rainy Season Transition Period in the Southern Congo Basin

Worden,

2024

Preprint

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The Congo basin hosts one of the largest terrestrial precipitation centers. Yet, the mechanisms that start the rainy seasons in Congo have not been studied systematically. We show that the transition from the dry to the rainy season over the southern Congo is initiated by a decrease in moisture export towards the Sahel, about three to four months before the rainy season onset (RSO), referred to as the pre-transition period. During this period, evapotranspiration (ET) is low due to low surface solar radiation, resulting from low insolation, and high amounts of low-level clouds. In the early transition period one to three months before the RSO, column water vapor and surface specific humidity increase due to increased oceanic moisture. Meanwhile, ET starts increasing for the first time due to increases in surface radiation and vegetation photosynthesis, despite a lack of soil moisture increases. Finally, in the late transition period about one month before the RSO, ET continues to increase, contributing equally to atmospheric moisture needed for deep convection as advected oceanic moisture. Additionally, the formation of the African Easterly-Jet South and the southward movement of the Congo Air Boundary increase vertical wind shear and provide large-scale dynamic lifting of the warm and humid air from the Congo. The frequency of deep convection increases rapidly, leading to the start of the rainy season. Therefore, the RSO over southern-hemispheric Congo basin is a result of combined large-scale atmospheric circulation change and vegetation response to the seasonal change of insolation.

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“…The southern hemisphere receives less rainfall during the dry season and more rainfall during the peak of the rainy season, resulting a greater seasonal variation than that of the northern hemisphere. P seasonality and interannual variations also differ between the western and eastern basin (e.g., Balas et al., 2007; Mba et al., 2022), particularly as mesoscale convective systems that provide much of the rainfall for the basin increase in frequency toward the equator and the interior of the continent (Jackson et al., 2009).…”

Section: Introductionmentioning

confidence: 99%

Congo Basin Water Balance and Terrestrial Fluxes Inferred From Satellite Observations of the Isotopic Composition of Water Vapor

Worden,

Bloom,

Worden

et al. 2024

Water Resources Research

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Large spatio‐temporal gradients in the Congo basin vegetation and rainfall are observed. However, its water‐balance (evapotranspiration minus precipitation, or ET − P) is typically measured at basin‐scales, limited primarily by river‐discharge data, spatial resolution of terrestrial water storage measurements, and poorly constrained ET. We use observations of the isotopic composition of water vapor to quantify the spatio‐temporal variability of net surface water fluxes across the Congo Basin between 2003 and 2018. These data are calibrated at basin scale using satellite gravity and total Congo river discharge measurements and then used to estimate time‐varying ET − P over four quadrants representing the Congo Basin, providing first estimates of this kind for the region. We find that the multi‐year record, seasonality, and interannual variability of ET − P from both the isotopes and the gravity/river discharge based estimates are consistent. Additionally, we use precipitation and gravity‐based estimates with our water vapor isotope‐based ET − P to calculate time and space averaged ET and net river discharge within the Congo Basin. These quadrant‐scale moisture flux estimates indicate (a) substantial recycling of moisture in the Congo Basin (temporally and spatially averaged ET/P > 70%), consistent with models and visible light‐based ET estimates, and (b) net river outflow is largest in the Western Congo where there are more rivers and higher flow rates. Our results confirm the importance of ET in modulating the Congo water cycle relative to other water sources.

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Central African Climate

Cited by 5 publications

References 69 publications

Seasonal variations in rain cells propagation over Central Africa and association with diurnal rainfall regimes

Seasonal variations in rain cells propagation over Central Africa and association with diurnal rainfall regimes

On the Mechanisms that Control the Rainy Season Transition Period in the Southern Congo Basin

Congo Basin Water Balance and Terrestrial Fluxes Inferred From Satellite Observations of the Isotopic Composition of Water Vapor

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