scholarly journals Analysis of spatial-temporal heterogeneity in remotely sensed aerosol properties observed during 2005–2015 over three countries along the Gulf of Guinea Coast in Southern West Africa

2018 ◽  
Vol 182 ◽  
pp. 313-324 ◽  
Author(s):  
Mangamana Aklesso ◽  
K. Raghavendra Kumar ◽  
Lingbing Bu ◽  
Richard Boiyo
Keyword(s):  
West Africa ◽  
Remotely Sensed ◽  
Temporal Heterogeneity ◽  
Gulf Of Guinea ◽  
Guinea Coast ◽  
Aerosol Properties

scholarly journals Understanding the variability of the rainfall dipole in West Africa using the EC-Earth last millennium simulation

2021 ◽  
Author(s):  
Qiong Zhang ◽  
Ellen Berntell ◽  
Qiang Li ◽  
Fredrik Charpentier Ljungqvist
Keyword(s):  
West Africa ◽  
Model Simulation ◽  
Rainfall Variability ◽  
Low Pressure ◽  
Last Millennium ◽  
Tropical Atlantic ◽  
Gulf Of Guinea ◽  
Dipole Pattern ◽  
Sahel Region ◽  
Heat Low

AbstractThere is a well-known mode of rainfall variability associating opposite hydrological conditions over the Sahel region and the Gulf of Guinea, forming a dipole pattern. Previous meteorological observations show that the dipole pattern varies at interannual timescales. Using an EC-Earth climate model simulation for last millennium (850–1850 CE), we investigate the rainfall variability in West Africa over longer timescales. The 1000-year-long simulation data show that this rainfall dipole presents at decadal to multidecadal and centennial variability and long-term trend. Using the singular value decomposition (SVD) analysis, we identified that the rainfall dipole present in the first SVD mode with 60% explained variance and associated with the variabilities in tropical Atlantic sea surface temperature (SST). The second SVD mode shows a monopole rainfall variability pattern centred over the Sahel, associated with the extra-tropical Atlantic SST variability. We conclude that the rainfall dipole-like pattern is a natural variability mode originated from the local ocean–atmosphere-land coupling in the tropical Atlantic basin. The warm SST anomalies in the equatorial Atlantic Ocean favour an anomalous low pressure at the tropics. This low pressure weakens the meridional pressure gradient between the Saharan Heat Low and the tropical Atlantic. It leads to anomalous northeasterly, reduces the southwesterly moisture flux into the Sahel and confines the Gulf of Guinea's moisture convergence. The influence from extra-tropical climate variability, such as Atlantic multidecadal oscillation, tends to modify the rainfall dipole pattern to a monopole pattern from the Gulf of Guinea to Sahara through influencing the Sahara heat low. External forcing—such as orbital forcing, solar radiation, volcanic and land-use—can amplify/dampen the dipole mode through thermal forcing and atmosphere dynamical feedback.

Ghana, Gulf of Guinea Coast

2021 ◽  
Vol 100 (sp1) ◽  
Author(s):  
Charles W. Finkl ◽  
Christopher Makowski
Keyword(s):  
Gulf Of Guinea ◽  
Guinea Coast

An 1804 Slaving Contract Signed in Arabic Script From the Upper Guinea Coast

1987 ◽  
Vol 14 ◽  
pp. 341-348 ◽  
Author(s):  
George E. Brooks ◽  
Bruce L. Mouser
Keyword(s):  
Nineteenth Century ◽  
West Africa ◽  
Rhode Island ◽  
Guinea Coast ◽  
Merchant Ship ◽  
Arabic Script ◽  
Slave Traders ◽  
Image Position

Few slaving agreements contracted between African sellers and American purchasers appear to have survived. They were rarely committed to paper, were destroyed after commitments were fulfilled, or were removed from business records kept by slave traders. The contract discussed here is of considerable interest as a document which, although brief, records important information and offers intriguing insights concerning African-European and African-African relationships in Guinea-Conakry at the turn of the nineteenth century.The slaving contract is dated 15 November 1804, and apparently was negotiated aboard the merchant ship Charlotte of Bristol, Rhode Island, Jonathan Sabens, master, anchored at the Iles de Los archipelago.Nov. th[ursday] 15-1804Shipe Charlottefortay days after date I Promas to pay Jno. Sabens or orde[r] nin[e] hundard and ni[ne]ty five Bars to be Pade in Rice and Slave Say fore tun of Rice at nity Bars par tun the Remandr in Slaves at one hundard and Twenty Bars par Slave.[signed in Arabic] Fadmod [Fendan Modu Dumbuya][signed in Arabic] Muhammad Sa'ab shokr Mohammed Sakib Fana/Ta/ Mohammed Shabaan(the month before Ramadan)Respecting the American traders involved, the Charlotte was jointly owned by George D'Wolf and Jonathan Sabens of Bristol, Rhode Island. Captain Jonathan Sabens was an experienced mariner, involved in at least three previous slaving voyages, including one as master of the Charlotte. Members of the D'Wolf family were associated with numerous slaving voyages to west Africa and continued to invest in slaving ventures long after Rhode Island made the trade illegal in 1787.

scholarly journals Interactions between Convection and a Moist Vortex Associated with an Extreme Rainfall Event over Southern West Africa

2019 ◽  
Vol 147 (7) ◽  
pp. 2309-2328 ◽  
Author(s):  
Marlon Maranan ◽  
Andreas H. Fink ◽  
Peter Knippertz ◽  
Sabastine D. Francis ◽  
Aristide B. Akpo ◽  
...  
Keyword(s):  
West Africa ◽  
Extreme Values ◽  
Vortex Formation ◽  
Daily Rainfall ◽  
Extreme Rainfall ◽  
Squall Line ◽  
Convective System ◽  
Extreme Rainfall Event ◽  
Guinea Coast ◽  
Free Atmosphere

Abstract An intense mesoscale convective system (MCS) in the Guinea Coast region caused one of the highest ever recorded daily rainfall amounts at the Nigerian station Abakaliki on 12 June 2016 (223.5 mm). This paper provides a detailed analysis of the meso- and synoptic-scale factors leading to this event, including some so far undocumented dynamical aspects for southern West Africa. The MCS formed over the Darfur Mountains due to diurnal heating, then moved southwestward along a mid- to lower-tropospheric trough, and developed into a classical West African squall line in a highly sheared environment with pronounced midlevel dryness. Strong moisture flux convergence over Nigeria prior to the MCS passage led to extreme values in precipitable water and was caused by the formation of a local, short-lived heat low. According to the pressure tendency equation, the latter resulted from tropospheric warming due to MCS-forced subsidence as well as surface insolation in the resulting almost cloud-free atmosphere. In this extremely moist environment, the MCS strongly intensified and initiated the formation of a lower-tropospheric vortex, which resulted in a deceleration of the MCS and high rainfall accumulation at Abakaliki. Following the vorticity equation, the vortex formation was realized through strong low-level vortex stretching and upper-level vertical vorticity advection related to the MCS, which became “dynamically large” compared to the Rossby radius of deformation. Eventually, moisture supply and lifting associated with the vortex are suggested to promote the longevity of the MCS during the subsequent westward movement along the Guinea Coast.

scholarly journals Local air pollution from oil rig emissions observed during the airborne DACCIWA campaign

2019 ◽  
Vol 19 (17) ◽  
pp. 11401-11411 ◽  
Author(s):  
Vanessa Brocchi ◽  
Gisèle Krysztofiak ◽  
Adrien Deroubaix ◽  
Greta Stratmann ◽  
Daniel Sauer ◽  
...  
Keyword(s):  
West Africa ◽  
Marine Boundary Layer ◽  
Dispersion Model ◽  
Particle Dispersion ◽  
Gulf Of Guinea ◽  
Aerosol Chemistry ◽  
Oil Platforms ◽  
Sensitivity Tests ◽  
Local Air Pollution ◽  
Oil Rig

Abstract. In the framework of the European DACCIWA (Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa) project, the airborne study APSOWA (Atmospheric Pollution from Shipping and Oil platforms of West Africa) was conducted in July 2016 to study oil rig emissions off the Gulf of Guinea. Two flights in the marine boundary layer were focused on the floating production storage and offloading (FPSO) vessel operating off the coast of Ghana. Those flights present simultaneous sudden increases in NO2 and aerosol concentrations. Unlike what can be found in flaring emission inventories, no increase in SO2 was detected, and an increase in CO is observed only during one of the two flights. Using FLEXPART (FLEXible PARTicle dispersion model) simulations with a regional NO2 satellite flaring inventory in forward-trajectory mode, our study reproduces the timing of the aircraft NO2 enhancements. Several sensitivity tests on the flux and the injection height are also performed, leading to the conclusion that a lower NO2 flux helps in better reproducing the measurements and that the modification of the injection height does not impact the results of the simulations significantly.

scholarly journals Identification of Potential Drought Areas in West Africa Under Climate Change and Variability

2019 ◽  
Vol 3 (3) ◽  
pp. 429-444 ◽  
Author(s):  
Gandome Mayeul L. D. Quenum ◽  
Nana A. B. Klutse ◽  
Diarra Dieng ◽  
Patrick Laux ◽  
Joël Arnault ◽  
...  
Keyword(s):  
West Africa ◽  
Climate Models ◽  
Potential Evapotranspiration ◽  
Standardized Precipitation Index ◽  
Global Climate Models ◽  
Spatiotemporal Pattern ◽  
Historical Period ◽  
Gulf Of Guinea ◽  
Precipitation Concentration ◽  
The Impact

Abstract The study investigates how the rising global temperature will affect the spatial pattern of rainfall and consequently drought in West Africa. The precipitation and potential evapotranspiration variables that are obtained from the Rossby Centre regional atmospheric model (RCA4) and driven by ten (10) global climate models under the RCP8.5 scenario were used. The model data were obtained from the Coordinated Regional Climate Downscaling Experiment (CORDEX) and analyzed at four specific global warming levels (GWLs) (i.e., 1.5 °C, 2.0 °C, 2.5 °C, and 3.0 °C) above the pre-industrial level. This study utilized four (4) indices: the standardized precipitation index, the precipitation concentration index, the precipitation concentration degree, and the precipitation concentration period over West Africa to explore the spatiotemporal variations in the characteristics of precipitation concentrations. Additionally, studying the impact of the four GWLs on consecutive dry days, consecutive wet days, and frequency of the intense rainfall events led to a better understanding of the spatiotemporal pattern of extreme precipitation. The results show that, at each GWL studied, the onset of rainfall comes 1 month earlier in the Gulf of Guinea compared to the historical period (1971–2000) with increasing rainfall intensity in the whole study domain, and the northeastern part of the study area becomes wetter. The rainfall concentration is uniformly distributed over the Gulf of Guinea and the Savanna zone for both the historical period and RCP8.5 scenario, while the Sahel zone which has shown an irregular concentration of rainfall for the historical period shows a uniform concentration of rainfall under all four GWLs.

scholarly journals A Multi-Sourced Data Retrodiction of Remotely Sensed Terrestrial Water Storage Changes for West Africa

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 401 ◽  
Author(s):  
Vagner Ferreira ◽  
Samuel Andam-Akorful ◽  
Ramia Dannouf ◽  
Emmanuel Adu-Afari
Keyword(s):  
West Africa ◽  
Water Storage ◽  
Remotely Sensed ◽  
Climate Indices ◽  
Terrestrial Water Storage ◽  
Drought Assessment ◽  
Grace Data ◽  
Short Period ◽  
Terrestrial Water ◽  
Land Data Assimilation System

Remotely sensed terrestrial water storage changes (TWSC) from the past Gravity Recovery and Climate Experiment (GRACE) mission cover a relatively short period (≈15 years). This short span presents challenges for long-term studies (e.g., drought assessment) in data-poor regions like West Africa (WA). Thus, we developed a Nonlinear Autoregressive model with eXogenous input (NARX) neural network to backcast GRACE-derived TWSC series to 1979 over WA. We trained the network to simulate TWSC based on its relationship with rainfall, evaporation, surface temperature, net-precipitation, soil moisture, and climate indices. The reconstructed TWSC series, upon validation, indicate high skill performance with a root-mean-square error (RMSE) of 11.83 mm/month and coefficient correlation of 0.89. The validation was performed considering only 15% of the available TWSC data not used to train the network. More so, we used the total water content changes (TWCC) synthesized from Noah driven global land data assimilation system in a simulation under the same condition as the GRACE data. The results based on this simulation show the feasibility of the NARX networks in hindcasting TWCC with RMSE of 8.06 mm/month and correlation coefficient of 0.88. The NARX network proved robust to adequately reconstruct GRACE-derived TWSC estimates back to 1979.

scholarly journals Local air pollution from oil rig emissions observed during the airborne DACCIWA campaign

2019 ◽  
Author(s):  
Vanessa Brocchi ◽  
Gisèle Krysztofiak ◽  
Adrien Deroubaix ◽  
Greta Stratmann ◽  
Daniel Sauer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
West Africa ◽  
Marine Boundary Layer ◽  
Emission Inventories ◽  
Gulf Of Guinea ◽  
Aerosol Chemistry ◽  
Oil Platforms ◽  
Sensitivity Tests ◽  
Local Air Pollution ◽  
Oil Rig

Abstract. In the framework of the European DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) project, the airborne study APSOWA (Atmospheric Pollution from Shipping and Oil platforms of West Africa) was conducted in July 2016 to study oil rig emissions off the Gulf of Guinea. Two flights in the marine boundary layer were focused on the floating production storage and offloading (FPSO) vessel operating off the coast of Ghana. Those flights present simultaneous sudden increases of NO2 and aerosols concentrations. Unlike what can be found in flaring emission inventories, no increase in SO2 was detected and an increase in CO is observed only during one of the two flights. Using FLEXPART simulations in forward trajectory mode, our study reproduced the timing of the aircraft NO2 enhancements. We used a regional NO2 satellite flaring inventory in the simulations, which showed an overall good estimate of flaring emission. Several sensitivity tests on the flux and the injection height were also performed to better reproduce the measurements.

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