The Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa Field Campaign: Overview and Research Highlights

Flamant, Cyrille; Knippertz, Peter; Fink, Andreas H.; Akpo, Aristide; Brooks, Barbara; Chiu, Christine; Coe, Hugh; Danuor, Sylvester K.; Evans, M. J.; Jegede, Olugbemiro J.; Kalthoff, Norbert; Konaré, A.; Liousse, Catherine; Lohou, Fabienne; Mari, C.; Schläger, Hans; Schwarzenböeck, Alfons; Adler, Bianca; Amekudzi, Leonard K.; Aryee, Jeffrey N. A.; Ayoola, Muritala A.; Batenburg, A. M.; Bessardon, Geoffrey; Borrmann, Stephan; Brito, Joel; Bower, Keith; Burnet, Frédéric; Catoire, Valéry; Colomb, A.; Denjean, Cyrielle; Fosu-Amankwah, Kwabena; Hill, Peter; Lee, J.; Lothon, Marie; Maranan, Marlon; Marsham, John H.; Meynadier, Rémi; Ngamini, Jean-Blaise; Rosenberg, Phil; Sauer, Daniel; Smith, V.; Stratmann, Greta; Taylor, Jonathan; Voigt, Christiane; Yoboue, Véronique

doi:10.1175/bams-d-16-0256.1

Cited by 78 publications

(120 citation statements)

References 25 publications

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“…The entire DACCIWA aircraft campaign fell into this period (see Flamant et al, 2017). The NSPD is positive through most of this phase and is modulated by the significant weather systems E-I, with centres between 12 and 16 • N and thus farther north than the Phase 1 features A-C (see Fig.…”

Section: Phase 2: Post-onset (22 June-20 July 2016)mentioning

confidence: 93%

“…Indications of aged aerosol particles were found when the DACCIWA research aircraft penetrated this layer over several days. These aged aerosol particles were likely from fires in the SH (Flamant et al, 2017). Interestingly the usually easterly 600-925 hPa shear vector backs to northerly just before the dry eventsignalling the changes in the 600 hPa circulation due to the vortex couplet.…”

Section: Phase 2: Post-onset (22 June-20 July 2016)mentioning

confidence: 99%

“…Field activities included measurements from three inland ground supersites (Savé in Benin, Kumasi in Ghana, Ile-Ife in Nigeria), urban sites (Cotonou in Benin, Abidjan in Côte d'Ivoire), radiosondes and three research aircraft stationed in Lomé (Togo). A detailed description of the field activities is given in Flamant et al (2017).…”

Section: Introductionmentioning

confidence: 99%

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A meteorological and chemical overview of the DACCIWA field campaign in West Africa in June–July 2016

et al. 2017

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Abstract. In June and July 2016 the Dynamics-AerosolChemistry-Cloud Interactions in West Africa (DACCIWA) project organised a major international field campaign in southern West Africa (SWA) including measurements from three inland ground supersites, urban sites in Cotonou and Abidjan, radiosondes, and three research aircraft. A significant range of different weather situations were encountered during this period, including the monsoon onset. The purpose of this paper is to characterise the large-scale setting for the campaign as well as synoptic and mesoscale weather systems affecting the study region in the light of existing conceptual ideas, mainly using objective and subjective identification algorithms based on (re-)analysis and satellite products. In addition, it is shown how the described synoptic variations influence the atmospheric composition over SWA through advection of mineral dust, biomass burning and urban pollution plumes.

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Section: Phase 2: Post-onset (22 June-20 July 2016)mentioning

confidence: 93%

Section: Phase 2: Post-onset (22 June-20 July 2016)mentioning

confidence: 99%

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A meteorological and chemical overview of the DACCIWA field campaign in West Africa in June–July 2016

et al. 2017

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“…In the coastal region of SWA mineral dust and biomass burning aerosols are generally observed above the ABL, between 800 and 600 hPa, as the result of long-range transport. Mineral dust is transported from the north in the Saharan air layer (Parker et al, 2005) (Flamant et al, 2009) and can be mixed downward into the ABL over the Sudanian region (Crumeyrolle et al,on the summer of 2014, which was the focus of one of the dry run exercises conducted in preparation for the field campaign that took place in June-July 2016 (Flamant et al, 2018). The period corresponds to the onset of the West African Monsoon (WAM) when the rainy convective systems migrate from the coastal area along the Gulf of Guinea to the Sahel (Williams et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Impact of biomass burning on pollutant surface concentrations in megacities of the Gulf of Guinea

et al. 2018

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Abstract. In the framework of the Dynamics-AerosolChemistry-Cloud Interactions in West Africa (DACCIWA) project, the tropospheric chemical composition in large cities along the Gulf of Guinea is studied using the Weather and Research Forecast and CHIMERE regional models. Simulations are performed for the May-July 2014 period, without and with biomass burning emissions. Model results are compared to satellite data and surface measurements. Using numerical tracer release experiments, it is shown that the biomass burning emissions in Central Africa are impacting the surface aerosol and gaseous species concentrations in Gulf of Guinea cities such as Lagos (Nigeria) and Abidjan (Ivory Coast). Depending on the altitude of the injection of these emissions, the pollutants follow different pathways: directly along the coast or over land towards the Sahel before being vertically mixed in the convective boundary layer and transported to the south-west and over the cities. In July 2014, the maximum increase in surface concentrations due to fires in Central Africa is ≈ 150 µg m −3 for CO, ≈ 10 to 20 µg m −3 for O 3 and ≈ 5 µg m −3 for PM 10 . The analysis of the PM 10 chemical composition shows that this increase is mainly related to an increase in particulate primary and organic matter.

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“…The campaign included ground-based measurements at three supersites in Ghana, Benin and Nigeria , radiosonde and aircraft measurements (Flamant et al, 2018). Knippertz et al (2017) presented the large-scale setting, synoptic and mesoscale weather systems, which affected the region during the DACCIWA campaign, identifying different phases of similar meteorological conditions, while Kalthoff et al (2018) gave an overview of the diurnal cycle of the ABL conditions as 5 well as of the conditions related to nocturnal LLC at three ground-based supersites.…”

Section: Introductionmentioning

confidence: 99%

The observed diurnal cycle of nocturnal low-level stratus clouds over southern West Africa: a case study

Babić

Adler

Kalthoff

et al. 2018

Preprint

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Abstract. This study presents the first detailed observational analysis of the complete diurnal cycle of stratiform low-level clouds (LLC) and involved atmospheric processes over southern West Africa. The data used here were collected during the comprehensive DACCIWA (Dynamics-Aerosol-Chemistry-Cloud-Interactions in West Africa) ground-based campaign, which aimed at monitoring LLC characteristics and capturing the wide range of atmospheric conditions related to the West African monsoon flow. In this study, in-situ and remote sensing measurements from the supersite near Savè (Benin) collected during a 5 typical day, which is characterized by the onset of a nocturnal low-level jet (NLLJ) and the formation of LLC, are analyzed.The associated dynamic and thermodynamic conditions allow the identification of five different phases of the LLC diurnal cycle: the Stable, Jet, Stratus I, Stratus II and Convective phase. The analysis of relative humidity tendency shows that cooling is a dominant process for LLC formation, which leads to a continuous increase of relative humidity at a maximum rate of 6 % per hour, until finally saturation is reached and LLC form with a cloud-base height near the height of NLLJ maximum. 10Results of heat budget analysis illustrate that horizontal cold air advection, related to the maritime inflow, which brings the cool maritime air mass and a prominent NLLJ wind profile, has the dominant role on the observed strong cooling of −1.2 K per hour during the Jet phase. The contribution from horizontal cold advection is quantified to be up to 72 %, while radiative cooling and sensible heat flux divergence contribute with 16 and 12 %, respectively, to the observed heat budget below the NLLJ maximum. After the LLC form (Stratus phase I and II), turbulent mixing is an important factor leading to the cooling 15 below the cloud base, while strong radiative cooling at the cloud top helps to maintain thick stratus.

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The Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa Field Campaign: Overview and Research Highlights

Cited by 78 publications

References 25 publications

A meteorological and chemical overview of the DACCIWA field campaign in West Africa in June–July 2016

A meteorological and chemical overview of the DACCIWA field campaign in West Africa in June–July 2016

Impact of biomass burning on pollutant surface concentrations in megacities of the Gulf of Guinea

The observed diurnal cycle of nocturnal low-level stratus clouds over southern West Africa: a case study

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