Observations of the impact of a major Saharan dust storm on the atmospheric radiation balance

Slingo, A.; Ackerman, Thomas P.; Allan, Richard P.; Kassianov, Evgueni I.; McFarlane, Sally A.; Robinson, G. J.; Barnard, James C.; Miller, Mark A.; Harries, J. E.; Russell, Jill; Dewitte, Steven

doi:10.1029/2006gl027869

Cited by 249 publications

(295 citation statements)

References 28 publications

(34 reference statements)

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“…At local scale, dust particles can clearly increase LW radiations at the surface by ∼20-30 W/m −2 , with maxima reaching up to 100 W/m −2 (not shown), what is consistent with the values reported by Bharmal et al (2009). At Niamey, Slingo et al (2006) reported that the downward thermal emission from the atmosphere display a significant peak on 7 March during the same dust outbreak.…”

Section: Infrared Spectral Rangesupporting

confidence: 80%

“…Such a decrease has been also observed by Slingo et al (2006) who reported that the dust storm dropped by around 250 W/m 2 the incoming solar fluxes at the surface at Niamey. Milton et al (2008) modelled that dust particles considerably reduce net downward shortwave flux at the surface over a large part of West Africa with maximum of 200 W/m 2 .…”

Section: Solar Spectral Rangementioning

confidence: 49%

“…At this time, we do not know the processes responsible for modifying cloud cover over the region, and more detailed studies on this specific point has to be performed. As reported by Slingo et al (2006), one process capable of modifying the clouds is the cold front that accompanied the dust outbreak.…”

Section: Solar Spectral Rangementioning

confidence: 99%

“…In parallel, experimental observations obtained at Djougou (Northern Benin) allowed to complement modelling simulations. Here, we perform a case study for an intense dust event occurring during March 2006 (Slingo et al, 2006;Milton et al, 2008;Tulet et al, 2008;McFarlane et al, 2009), leading to dust aerosol optical depth (AOD) larger than 2 (at 550 nm) over a large part of West Africa.…”

Section: Introductionmentioning

confidence: 99%

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Impact of dust aerosols on the radiative budget, surface heat fluxes, heating rate profiles and convective activity over West Africa during March 2006

et al. 2009

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Abstract. The present work analyses the effect of dust aerosols on the surface and top of atmosphere radiative budget, surface temperature, sensible heat fluxes, atmospheric heating rate and convective activity over West Africa. The study is focused on the regional impact of a major dust event over the period of 7-14 March 2006 through numerical simulations performed with the mesoscale, nonhydrostatic atmospheric model MesoNH. Due to its importance on radiative budgets, a specific attention has been paid to the representation of dust single scattering albedo (SSA) in MesoNH by using inversions of the AErosol RObotic NETwork (AERONET). The radiative impacts are estimated using two parallel simulations, one including radiative effects of dust and the other without them. The simulations of dust aerosol impacts on the radiative budget indicate remarkable instantaneous (at midday) decrease of surface shortwave (SW) radiations over land, with regional (9 • -17 • N, 10 • W-20 • E) mean of −137 W/m 2 during the 9 to 12 March period. The surface dimming resulting from the presence of dust is shown to cause important reduction of both surface temperature (up to 4 • C) and sensible heat fluxes (up to 100 W/m 2 ), which is consistent with experimental observations. At the top of the atmosphere, the SW cooling (regional mean of

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Section: Infrared Spectral Rangesupporting

confidence: 80%

Section: Solar Spectral Rangementioning

confidence: 49%

Section: Solar Spectral Rangementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of dust aerosols on the radiative budget, surface heat fluxes, heating rate profiles and convective activity over West Africa during March 2006

et al. 2009

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“…The downwelling SW and LW radiative fluxes at the surface measured by the AMF are used in this study. Uncertainties in the AMF measured radiative fluxes are given by Slingo et al (2006) as 9.0 W m −2 for the total downwelling shortwave, although this could be as large as 25 W m −2 during dust storms, and 5.1 W m −2 for the downwelling longwave.…”

Section: Arm Mpl Lidarmentioning

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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Evidence of a weakly absorbing intermediate mode of aerosols in AERONET data from Saharan and Sahelian sites

et al. 2013

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Accurate retrievals of aerosol size distribution are necessary to estimate aerosols' impact on climate and human health. The inversions of the Aerosol Robotic Network (AERONET) usually retrieve bimodal distributions. However, when the inversion is applied to Saharan and Sahelian dust, an additional mode of intermediate size between the coarse and fine modes is sometimes seen. This mode explains peculiarities in the behavior of the Ångström exponent, along with the fine mode fraction retrieved using the spectral deconvolution algorithm, observed in a March 2006 dust storm. For this study, 15 AERONET sites in northern Africa and on the Atlantic are examined to determine the frequency and properties of the intermediate mode. The mode is observed most frequently at Ilorin in Nigeria. It is also observed at Capo Verde and multiple sites located within the Sahel but much less frequently at sites in the northern Sahara and the Canary Islands. The presence of the intermediate mode coincides with increases in Ångström exponent, fine mode fraction, single‐scattering albedo, and to a lesser extent percent sphericity. The Ångström exponent decreases with increasing optical depth at most sites when the intermediate mode is present, but the fine mode fraction does not. Single‐scattering albedo does not steadily decrease with fine mode fraction when the intermediate mode is present, as it does in typical mixtures of dust and biomass‐burning aerosols. Continued investigation is needed to further define the intermediate mode's properties, determine why it differs from most Saharan dust, and identify its climate and health effects.

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Observations of the impact of a major Saharan dust storm on the atmospheric radiation balance

Cited by 249 publications

References 28 publications

Impact of dust aerosols on the radiative budget, surface heat fluxes, heating rate profiles and convective activity over West Africa during March 2006

Impact of dust aerosols on the radiative budget, surface heat fluxes, heating rate profiles and convective activity over West Africa during March 2006

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

Evidence of a weakly absorbing intermediate mode of aerosols in AERONET data from Saharan and Sahelian sites

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