African Monsoon Multidisciplinary Analysis: An International Research Project and Field Campaign

Redelsperger, Jean‐Luc; Thorncroft, Chris D.; Diedhiou, Arona; Lebel, Thierry; Parker, Douglas J.; Polcher, Jan

doi:10.1175/bams-87-12-1739

Cited by 658 publications

(522 citation statements)

References 12 publications

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“…In this study, we use a version of WRF (WRF-Chem) that simulates trace gases and particulates simultaneously with the meteorological fields (Grell et al, 2005). Zhao et al (2010) investigated the sensitivity of the WRF-Chem simulated dust radiative forcings to dust emission and aerosol schemes and evaluated the model results using data from the African Monsoon Multidisciplinary Analysis (AMMA) campaign, which is a major international campaign in 2006 to improve understanding of climate, monsoon, and hydrological cycle of West Africa and the impacts from aerosols (Redelsperger et al, 2006). Following a similar modeling approach as Zhao et al (2010), the objective of this study is to further understand the various radiative forcings of Saharan dust and how they jointly affect the surface energy budget, atmospheric diabatic heating, and hydrological cycle at a regional scale.…”

Section: Introductionmentioning

confidence: 99%

Radiative impact of mineral dust on monsoon precipitation variability over West Africa

et al. 2011

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Abstract. The radiative forcing of dust and its impact on precipitation over the West Africa monsoon (WAM) region is simulated using a coupled meteorology and aerosol/chemistry model (WRF-Chem). During the monsoon season, dust is a dominant contributor to aerosol optical depth (AOD) over West Africa. In the control simulation, on 24-h domain average, dust has a cooling effect (−6.11 W m −2 ) at the surface, a warming effect (6.94 W m −2 ) in the atmosphere, and a relatively small TOA forcing (0.83 W m −2 ). Dust modifies the surface energy budget and atmospheric diabatic heating. As a result, atmospheric stability is increased in the daytime and reduced in the nighttime, leading to a reduction of late afternoon precipitation by up to 0.14 mm/h (25%) and an increase of nocturnal and early morning precipitation by up to 0.04 mm/h (45%) over the WAM region. Dust-induced reduction of diurnal precipitation variation improves the simulated diurnal cycle of precipitation when compared to measurements. However, daily precipitation is only changed by a relatively small amount (−0.17 mm/day or −4%). The dust-induced change of WAM precipitation is not sensitive to interannual monsoon variability. On the other hand, sensitivity simulations with weaker to stronger absorbing dust (in order to represent the uncertainty in dust solar absorptivity) show that, at the lower atmosphere, dust longwave warming effect in the nighttime surpasses its shortwave cooling effect in the daytime; this leads to a less stable atmosphere associated with more convective precipitation in the nighttime. As a result, the dust-induced change of daily WAM precipitation varies from a significant reduction of −0.52 mm/day (−12%, weaker absorbing dust) to a small increase of 0.03 mm/day (1%, stronger absorbing dust). This variation originates from the competition between dust impact on daytime and nightCorrespondence to: C. Zhao (chun.zhao@pnl.gov) time precipitation, which depends on dust shortwave absorption. Dust reduces the diurnal variation of precipitation regardless of its absorptivity, but more reduction is associated with stronger absorbing dust.

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Section: Introductionmentioning

confidence: 99%

Radiative impact of mineral dust on monsoon precipitation variability over West Africa

et al. 2011

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“…The aircraft was operated from Niamey (Niger) between 10 January and 3 February 2006 in the framework of the first Special Observation Period (SOP0) of the African Monsoon Multidisciplinary Analyses (AMMA) project [Redelsperger et al, 2006]. This experiment aimed to assess the direct radiative impact of mineral dust at the regional scale of western Africa.…”

Section: Introductionmentioning

confidence: 99%

Size distribution, shape, and composition of mineral dust aerosols collected during the African Monsoon Multidisciplinary Analysis Special Observation Period 0: Dust and Biomass‐Burning Experiment field campaign in Niger, January 2006

Chou¹,

Formenti²,

Maillé³

et al. 2008

J. Geophys. Res.

184

245

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[1] Dust samples were collected onboard the UK community BAe-146 research aircraft of the Facility for Airborne Atmospheric Measurements (FAAM) operated over Niger during the winter Special Observation Period of the African Monsoon Multidisciplinary Analysis project (AMMA SOP0/DABEX). Particle size, morphology, and composition were assessed using single-particle analysis by analytical scanning and transmission electron microscopy. The aerosol was found to be composed of externally mixed mineral dust and biomass burning particles. Mineral dust consists mainly of aluminosilicates in the form of illite and kaolinite and quartz, accounting for up to 80% of the aerosol number. Fe-rich particles (iron oxides) represented 4% of the particle number in the submicron fraction. Diatoms were found on all the samples, suggesting that emissions from the Bodélé depression were also contributing to the aerosol load. Satellite images confirm that the Bodélé source was active during the period of investigation. Biomass burning aerosols accounted for about 15% of the particle number of 0.1-0.6 mm diameter and were composed almost exclusively of particles containing potassium and sulfur. Soot particles were very rare. The aspect ratio AR is a measure of particle elongation. The upper limit of the AR value distribution is 5 and the median is 1.7, which suggests that mineral dust particles could be described as ellipsoids whose major axis never exceeds 1.9 Â D p (the spherical geometric diameter). This is consistent with other published values for mineral dust, including the recent Aerosol Robotic Network retrieval results of Dubovik et al. (2006).

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“…More recently, the African Monsoon Multidisciplinary Analyses (AMM+A: Redelsperger et al, 2006) campaign was organized to 'improve our knowledge and understanding of the West African monsoon'. The release of the International Science Plan for the second phase of AMMA (2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020); http://www.amma-international.org/ IMG/pdf/ISP2 v2.pdf) summarized results from the first phase and stated the need to understand not only the meridional, but zonal characteristics of the WAM along the spectrum of phenomena that make up the WAM system.…”

Section: Introductionmentioning

confidence: 99%

Regional comparison of West African convective characteristics: a TRMM‐based climatology

Guy

Rutledge

2011

Quart J Royal Meteoro Soc

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A 13-year (1998-2010) climatology of mesoscale convective characteristics associated with the West African monsoon are investigated using precipitation radar and passive microwave data from the NASA Tropical Rainfall Measuring Mission satellite. Seven regions defined as continental northeast and northwest, southeast and southwest, coastal, and maritime north and south are compared to analyse zonal and meridional differences. Data are categorized according to identified African easterly wave (AEW) phase and when no wave is present. While some enhancements are observed in association with AEW regimes, regional differences were generally more apparent than wave vs. no-wave differences. Convective intensity metrics confirm that land-based systems exhibit stronger characteristics, such as higher storm top and maximum 30 dBZ heights and significant 85 GHz brightness temperature depressions. Continental systems also contain a lower fraction of points identified as stratiform. Results suggest that precipitation processes also varied depending upon region and AEW regime, with warm-rain processes more apparent over the ocean and the southwest continental region and ice-based microphysics more dominant over land, including mixed-phase processes. AEW regimes did show variability in stratiform fraction and ice and liquid water content, suggesting modulation of mesoscale characteristics possibly through feedback with the synoptic environment.

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African Monsoon Multidisciplinary Analysis: An International Research Project and Field Campaign

Cited by 658 publications

References 12 publications

Radiative impact of mineral dust on monsoon precipitation variability over West Africa

Radiative impact of mineral dust on monsoon precipitation variability over West Africa

Size distribution, shape, and composition of mineral dust aerosols collected during the African Monsoon Multidisciplinary Analysis Special Observation Period 0: Dust and Biomass‐Burning Experiment field campaign in Niger, January 2006

Regional comparison of West African convective characteristics: a TRMM‐based climatology

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