Mesoscale convective systems in the Congo Basin: seasonality, regionality, and diurnal cycles

Andrews, Patrick C.; Cook, Kerry H.; Vizy, Edward K.

doi:10.1007/s00382-023-06903-7

Cited by 6 publications

(7 citation statements)

References 34 publications

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“…Moisture advection, both horizontal and vertical, is a critical factor in understanding the hydrological cycle of the Congo Basin. Andrews et al (2023) demonstrated that in the Congo Basin, the peaks of seasonal and diurnal mesoscale convective systems (MCSs) coincide with the instability observed in the MSE profiles in the lower layers. In this section, we delve into the mechanisms of MSE advection within the basin.…”

Section: Long-term Climatology Of Mse Advectionmentioning

confidence: 94%

“…The Moist Static Energy (MSE) budget has been identified as a useful tool for understanding the atmosphere perturbation related to moisture transport (Adames & Ming, 2018;Andrews et al, 2023;Nana et al, 2023;Wang & Li, 2020a, 2020b. The MSE is a mixture of thermal, potential and latent energies used to assess the energetic anomalies of convective anomalies associated with precipitation (Bui et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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Processes behind the decrease in Congo Basin precipitation during the rainy seasons inferred from ERA‐5 reanalysis

Kenfack,

Tamoffo,

Tchotchou

et al. 2024

Intl Journal of Climatology

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The ongoing Congo Basin drying is linked to decreasing atmospheric water vapour. To comprehend the processes reducing precipitation, we analysed water and Moist Static Energy components, associated with heating sources using ERA5 reanalysis data over the period 1981–2022. The findings reveal that the precipitation deficit in the Congo Basin during March–April–May and September–October–November is primarily attributed to a decreasing trend in the vertical moisture advection anomaly induced by vertical velocity anomalies. Following this, a horizontal moisture advection anomaly induced by specific humidity anomalies plays a significant role. However, evaporation, horizontal moisture advection anomalies induced by wind anomalies, and vertical moisture advection anomalies induced by specific humidity anomalies do not appear to contribute significantly to the drying trend in the region. The horizontal propagation of MSE advection anomalies exhibits a similar pattern to that of moisture flux advection anomalies, both at different boundaries and within the basin itself. Conversely, the contribution of vertical advection of MSE anomalies remains weak. By integrating moisture and MSE budgets, we interpret the declining precipitation trend as a consequence of uplift driven by horizontal MSE advection. Furthermore, our analysis indicates a decreasing trend in the atmospheric heating source within the basin in association with reduced precipitation. This reduction could signify a decrease in moisture influx into the basin, thereby providing more explanations for the observed drying.

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Section: Long-term Climatology Of Mse Advectionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Processes behind the decrease in Congo Basin precipitation during the rainy seasons inferred from ERA‐5 reanalysis

Kenfack,

Tamoffo,

Tchotchou

et al. 2024

Intl Journal of Climatology

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“…These nighttime rains are still not well understood. Andrews et al (2024) found that MCS rainfall shows a unimodal diurnal cycle in the equinoctial seasons (peak at 16:00/17:00 LST and minimum at 05:00/06:00 LST) but inhomogeneous patterns in the solsticial seasons. Late night hours display a slightly higher contribution of MCSs to total rainfall.…”

Section: Introductionmentioning

confidence: 96%

“…In both seasons, patterns of MCSs displacement match spatially the 650 hPa fields of average wind and vertical shear. Andrews et al (2024) analysed the MCSs contribution to total rainfall over the Congo Basin using 20 years of IMERG precipitation estimates. A 80% contribution was found over the continental interior throughout the year.…”

Section: Introductionmentioning

confidence: 99%

“…It is expected that these diurnal regimes strongly depend on the development and propagation of rain cells. Many parts of Central Africa are characterized by a dominant late afternoon rainfall maximum (Dezfuli, 2017;Vondou et al, 2017), related to daytime convection and to MCSs occurrence (Andrews et al, 2024;Jackson et al, 2009). The diurnal cycle of MCSs shows maximum frequency around 15:00-21:00 LST, but there is substantial MCS activity at night, during which volumetric rain per MCS increases.…”

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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Characteristics of Station‐Derived Convective Cold Pools Over Equatorial Africa

Hoeller,

Haerter,

Da Silva

2024

Geophysical Research Letters

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Due to their potential role in organizing tropical mesoscale convective systems, a better understanding of cold pool (CP) dynamics in such regions is critical, particularly over land where the diurnal cycle further concentrates convective activity. Numerical models help disentangle the processes involved but often lack observational benchmarks. To close this gap, we analyze nearly 43 years of five‐minute resolution near‐surface timeseries, recorded from 12 automatic weather stations across equatorial Africa during 2019–2023. We identify 4,218 CPs based on criteria for temperature and wind. The identified CP gust fronts, which exhibit respective median temperature and specific humidity decreases of 5.3 K and 2.8 g kg−1, closely correlate with satellite‐observed brightness temperature discontinuities. Despite weak diurnal variation in precipitation, observed CP occurrence shows a pronounced diurnal cycle with an afternoon peak — a feature we attribute to low‐level moisture conditions. Our findings can serve as observational benchmark to improve simulations of CP organization.

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Mesoscale convective systems in the Congo Basin: seasonality, regionality, and diurnal cycles

Cited by 6 publications

References 34 publications

Processes behind the decrease in Congo Basin precipitation during the rainy seasons inferred from ERA‐5 reanalysis

Processes behind the decrease in Congo Basin precipitation during the rainy seasons inferred from ERA‐5 reanalysis

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

Characteristics of Station‐Derived Convective Cold Pools Over Equatorial Africa

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