Analyzing intensifying thunderstorms over the Congo Basin using the Gálvez-Davison index from 1983–2018

Alber, Kathrin; Raghavendra, Ajay; Zhou, Liming; Jiang, Yan; Sussman, Heather S.; Solimine, Stephen

doi:10.1007/s00382-020-05513-x

Cited by 12 publications

(6 citation statements)

References 55 publications

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“…Thus, the model patterns of the convection both in WCEA and ECEA match well with their dipole rainfall biases. However, it should be noted that although an increase in vertical motion is a strong indication of tropical convection, enhanced convection does not necessarily mean a strengthened rainfall over the Congo basin (WCEA; Hamada et al 2015;Raghavendra et al 2018;Alber et al 2021). These studies showed increased thunderstorms over the WCEA, but contrastingly with the observed drying trend.…”

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confidence: 97%

Mechanisms of Rainfall Biases in Two CORDEX-CORE Regional Climate Models at Rainfall Peaks over Central Equatorial Africa

et al. 2022

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Two regional climate models (RCMs) participating in the CORDEX-Coordinated Output for Regional Evaluations (CORDEX-CORE) project feature a dipole-type rainfall bias during March-May (MAM) and September-November (SON) over Central Equatorial Africa (CEA), consisting in positive bias in West Central Equatorial Africa (WCEA) and negative bias in East Central Equatorial Africa (ECEA). One is the REgional MOdel version 2015 (REMO2015), and the other is the fourth version of the Regional Climate Model (RegCM4-v7). RCMs are nested in three Earth System Models (ESMs) from the Coupled Model Intercomparison Project phase 5 (CMIP5), and in the reanalysis ERA-Interim, at ~25 Km spacing-grid resolution. This study highlights misrepresented underlying physical processes associated with these rainfall biases through a process-based evaluation. Both RCMs produce a weaker Congo basin cell, associated with a weaker land-ocean zonal surface pressure gradient. Consequently, less water vapour enters the region, and little amount is transported from WCEA to ECEA, resulting in higher moisture availability in the west than in the east. This leads to an unevenly distributed moisture across the region, favouring a stronger atmospheric instability in WCEA where the moist static energy (MSE) anomalously increases through an enhanced latent static energy (LSE). Moisture arrives at a slower pace in ECEA, associated with the weak cell's strength. The intensity of ascent motions in response to the orographic constraint is weak to destabilise atmospheric stability in the lower layers, necessary for initiating deep convection. Therefore, the convection is shallow in ECEA related to underestimating the MSE due to the reduced LSE.

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confidence: 97%

Mechanisms of Rainfall Biases in Two CORDEX-CORE Regional Climate Models at Rainfall Peaks over Central Equatorial Africa

et al. 2022

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“…However, this is not the case in equatorial Africa (Hamada et al., 2015), or at least in CEA. A number of studies (e.g., Alber et al., 2021; Raghavendra et al., 2018) showed that despite the increasing trend in thunderstorms over the Congo basin, the rainfall trend is contrastingly decreasing, leading to a drying of the Congo rainforest. Convection‐permitting modelling (CPM) is a promising approach to simulating precipitation features across Africa because it connects better deep convection and precipitation variability (Lucas‐Picher et al., 2021).…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of Added Value of a Coupled Global Ocean‐Regional Atmosphere Climate Model Over Central Equatorial Africa

Tamoffo,

Weber,

Cabos

et al. 2024

JGR Atmospheres

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There is an urgent need to enhance climate projections for Central Equatorial Africa (CEA), given the region's high vulnerability to climatic hazards and its economy's heavy dependence on climate‐sensitive sectors. This study aims to evaluate the performance of the regional earth system model ROM, composed of the atmosphere‐only regional climate model (RCM) REMO coupled with the global Max Planck Institute for Meteorology Ocean Model (MPIOM), in reproducing the precipitation climatology over CEA. ROM results are compared to those of REMO in two sets of experiments, one driven by the ERA‐Interim reanalysis and the other by the MPI‐ESM‐LR earth system model (ESM), both at ∼25‐km horizontal resolution. Results show that ocean coupling improves rainfall climatology thanks to a better representation of the physical processes and mechanisms underlying the rainfall system. In particular, an improved sea surface temperature (SST) results in a more realistic simulation of land‐atmosphere‐ocean interactions, and subsequently the atmospheric baroclinicity. Specifically, the coupling reduces the positive SST bias inherited by the driving ESM across the entire Guinea Gulf and Benguela‐Angola coastal seas. This leads to better simulated land‐ocean thermal and pressure contrasts. Improvements in land‐ocean contrasts, in turn, enhance the representation of the regional atmospheric circulation, and thus precipitation. Interestingly, the coupling is more beneficial when ROM is driven by the ESM than the reanalysis. This study emphasizes the advantage of dynamically downscaling ESMs using regional earth system models rather than atmosphere‐only RCMs, with the potential to enhance confidence in future climate projections.

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“…In summary, the results of correlations and compositions reveal the limitations of parameters in their association with CSL frequency. However, they still prove useful in identifying other influential processes related to the ocean and the atmosphere, with low correlation and attribution values similar to studies in other tropical regions (Miller et al, 2019b;Alber et al, 2020).…”

Section: Compositions and Parameter Correlationmentioning

confidence: 92%

Influence of sea stratification and troposphere stability over the Coastal Squall Lines of Eastern Amazon

Silva,

de Camargo,

Veleda

et al. 2024

Preprint

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This study investigates the relationship between oceanic and atmospheric parameters and their relation with the occurrence of Coastal Squall Lines (CSL) in the Eastern Amazon. Utilizing a minimalist set of stability and stratification parameters, results indicate a significant coherence in the 8 and 12-month period in bulk parameters, potentially linked to the discharge of the Amazon River and the convective regime of Western Tropical Atlantic. A cross-wavelet analysis shed light on the relation of CSL frequency with the local and remote oceanic stratification and atmosphere stability parameters. Additionally, composite analyses reveal shifts in the distributions of these parameters during CSL occurrences, highlighting the sensitivity of CSL to environmental variables. These outcomes reveal the need to consider the influence of local shelf sea stratification to enhance the precision of CSL characterization. While this study covers this gap, further research considering the mechanistic approach is needed to improve the understanding of mesoscale convection at the Eastern Amazon.

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Analyzing intensifying thunderstorms over the Congo Basin using the Gálvez-Davison index from 1983–2018

Cited by 12 publications

References 55 publications

Mechanisms of Rainfall Biases in Two CORDEX-CORE Regional Climate Models at Rainfall Peaks over Central Equatorial Africa

Mechanisms of Rainfall Biases in Two CORDEX-CORE Regional Climate Models at Rainfall Peaks over Central Equatorial Africa

Mechanisms of Added Value of a Coupled Global Ocean‐Regional Atmosphere Climate Model Over Central Equatorial Africa

Influence of sea stratification and troposphere stability over the Coastal Squall Lines of Eastern Amazon

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