The Rainfall and Convective Regime over Equatorial Africa, with Emphasis on the Congo Basin

Nicholson, Sharon E.

doi:10.1002/9781119657002.ch3

Cited by 8 publications

(9 citation statements)

References 63 publications

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“…Jackson et al (2009) also noted a substantial MCS activity at night, especially in the central Congo Basin. Nicholson (2022) noted that this nighttime rainfall peak is much less common in Amazonia than in Central Africa. In the Sahel, while a vast majority of nocturnal rainfall occurrence is associated with the propagation of MCSs developed in the afternoon, cases of nighttime MCSs exist which are still poorly understood but partly dependent on the Intertropical Front location (Vizy & Cook, 2018).…”

Section: Resultsmentioning

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).…”

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: Resultsmentioning

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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“…Finally, we calculate the moisture convergence term (-𝑞 × 𝛻. 𝑉) and moisture transport vectors (𝑞𝑉) at four pressure levels to represent near surface, lower-troposphere, mid-troposphere, and upper troposphere, respectively: 925 hPa, 850 hPa, 700 hPa, and 650 hPa, similar to that in Cook and Vizy (2022) and Nicholson (2022). This is because moisture transport varies substantially between near surface atmosphere, lower troposphere, and middle troposphere, including its source regions.…”

Section: Thermodynamic and Dynamic Equationsmentioning

confidence: 99%

“…Precipitation in that region feeds Congo River, the world's second largest river by discharge volume, and sustains the world's second largest contiguous rainforest. Rainfall varies on interannual to decadal scales about 6-10% over the central Congo basin and up to 20% of in the outskirts of the basin (Mahé 1995;Nicholson 2022). Many previous studies have focused on the mechanisms that controls rainfall during the rainy seasons in the Congo Basin, as better understanding how these mechanisms change due to natural climatic and anthropogenic influences will lead to better understanding of how the rainy seasons will evolve in the future (e.g., Cook and Vizy 2022).…”

Section: Introductionmentioning

confidence: 99%

“…Nicholson 2022, Hastenrath 2007, Cook and Vizy 2016, Neupane 2016, Washington et al, 2013, Dezfuli, 2017, Longandjo and Rouault, 2020, Howard and Washington, 2019. The midlevel African Easterly Jet North and South (AEJ-N and AEJ-S, respectively) appear to control the meridional position of the tropical rain belt (Nicholson and Grist 2003, Kuete et al, 2020, Jackson et al, 2009, Nicholson 2022.…”

Section: Introductionmentioning

confidence: 99%

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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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Assessment of uncertainties in reanalysis datasets in reproducing thermodynamic mechanisms in the moisture budget’s provision in the Congo Basin

Kenfack,

Tamoffo,

Djiotang Tchotchou

et al. 2023

Theor Appl Climatol

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The Rainfall and Convective Regime over Equatorial Africa, with Emphasis on the Congo Basin

Cited by 8 publications

References 63 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

Assessment of uncertainties in reanalysis datasets in reproducing thermodynamic mechanisms in the moisture budget’s provision in the Congo Basin

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