Motivation, rationale and key results from the GERBILS Saharan dust measurement campaign

Haywood, Jim M.; Johnson, Ben; Osborne, S.; Baran, Anthony J.; Brooks, M. E.; Milton, Sean; Mulcahy, Jane; Walters, David; Allan, Richard P.; Klaver, Anne; Formenti, Paola; Brindley, Helen E.; Christopher, S. A.; Gupta, Pawan

doi:10.1002/qj.797

Cited by 62 publications

(52 citation statements)

References 51 publications

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“…Moreover, similar high values of single scattering albedo has also been reported in literature under high dust loading (Li et al, 2004;Mallet et al, 2009;Prasad et al, 2007;Markowicz et al, 2008). The asymmetry parameter g is assigned a standard value of 0.73, which is most commonly used for mineral dust (Sokolik and Toon, 1999;Quijano et al, 2000;Haywood et al, 2011;Andrews et al, 2006). The HV and relative humidity (RH) were obtained from the hourly meteorological data.…”

Section: Input Parametersmentioning

confidence: 70%

“…Furthermore, radiative forcing by dust particles modulate the low-level jet resulting in a diurnal variation of dust emission over arid and semi-arid regions (Alizadeh Choobari et al, 2013). A lot of ground-based and airborne measurement campaigns mainly in the African, Mediterranean and Asian regions have been conducted in recent years to analyze the optical and physical properties of dust aerosols (Sabbah et al, 2001;Ahn et al, 2007;Heinold et al, 2008;Kaskaoutis et al, 2008;McConnell et al, 2008;Osborne et al, 2008;Ansmann et al, 2011;Haywood et al, 2011), the frequency of dust outbreaks (Goudie and Middleton, 1992;Gao et al, 2003;Kutiel andFruman 2003, Rezazadeh et al, 2013) and their sources and transport range (Youlin et al, 2002;El-Askary et al, 2003, Washington et al, 2003Xuana et al, 2004;Tsolmon et al, 2008;Rashki et al, 2012;Notaro et al, 2013). Several case studies of dust outbreaks have been conducted in which direct radiative forcing at the surface and at top of the atmosphere (TOA) have been calculated using ground-based and satellite-based data (Xu et al, 2003;Costa et al, 2006;Prasad et al, 2007;Di Sarra et al, 2008;Markowicz et al, 2008;Pandithurai et al, 2008;Di Biagio et al, 2010;Lemaître et al, 2010;Park et al, 2010;Sharma et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Aerosol's optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study

Saeed

Al‐Dashti²,

Spyrou

2014

Atmos. Chem. Phys.

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Abstract. Dust aerosols are analyzed for their optical and physical properties during an episode of a dust storm that blew over Kuwait on 26 March 2003 when the military Operation Iraqi Freedom was in full swing. The intensity of the dust storm was such that it left a thick suspension of dust throughout the following day, 27 March. The synoptic sequence leading to the dust storm and the associated wind fields are discussed. Ground-based measurements of aerosol optical thickness reached 3.617 and 4.17 on 26 and 27 March respectively while the Ångstrom coefficient, α 870/440 , dropped to −0.0234 and −0.0318. Particulate matter concentration of 10 µm diameter or less, PM 10 , peaked at 4800 µg m −3 during dust storm hours of 26 March. Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved aerosol optical depth (AOD) by Deep Blue algorithm and Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) exhibited high values. Latitude-longitude maps of AOD and AI were used to deduce source regions of dust transport over Kuwait. The vertical profile of the dust layer was simulated using the SKIRON atmospheric model. Instantaneous net direct radiative forcing is calculated at top of atmosphere (TOA) and surface level. The thick dust layer of 26 March resulted in cooling the TOA by −60 Wm −2 and surface level by −175 Wm −2 for a surface albedo of 0.35. Slightly higher values were obtained for 27 March due to the increase in aerosol optical thickness. Radiative heating/cooling rates in the shortwave and longwave bands were also examined. Shortwave heating rate reached a maximum value of 2 K day −1 between 3 and 5 km, dropped to 1.5 K day −1 at 6 km and diminished at 8 km. Longwave radiation initially heated the lower atmosphere by a maximum value of 0.2 K day −1 at surface level, declined sharply at increasing altitude and diminished at 4 km. Above 4 km longwave radiation started to cool the atmosphere slightly reaching a maximum rate of −0.1 K day −1 at 6 km.

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Section: Input Parametersmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Aerosol's optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study

Saeed

Al‐Dashti²,

Spyrou

2014

Atmos. Chem. Phys.

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“…and Shortwave radiation (GERBILS; Haywood et al, 2011). Some of the data discussed in this paper have been published previously (Formenti et al, , 2011bRajot et al, 2008;Klaver et al, 2011).…”

Section: P Formenti Et Al: Mapping the Physico-chemical Properties mentioning

confidence: 99%

“…This discrepancy could be reconciled by including mineral dust in the model. The GERBILS experiment, whose full rationale and operating details are described in Haywood et al (2011), was therefore designed to test this hypothesis, and to determine the properties of the mineral dust to be included in the model. The experiment consisted of 10 research flights onboard the FAAM BAe-146, performed between Nouakchott (18.10 • N, 15.94 • W; Mauritania) and Niamey (13.48 • N, 2.18 • E; Niger) on an almost constant route along the 18 • N meridian.…”

Section: Field Campaignsmentioning

confidence: 99%

“…The prospective evolution of this data set will be the inclusion of data from other field campaigns, both close to source regions and at some distance. Amongst these are the Fennec and the SAMUM (Saharan Mineral Dust Experiment) field campaigns (Heintzenberg et al, 2009;Ansmann et al, 2011;Washington et al, 2012), which were conducted at downwind sources in Algeria and Morocco and were relevant to large-scale transport (Caquineau et al, 2002). This will require a close-up examination of experimental protocols and a careful evaluation of their influence on the results.…”

Section: Final Remarks Conclusion and Perspectivesmentioning

confidence: 99%

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Mapping the physico-chemical properties of mineral dust in western Africa: mineralogical composition

et al. 2014

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Abstract. In the last few years, several ground-based and airborne field campaigns have allowed the exploration of the properties and impacts of mineral dust in western Africa, one of the major emission and transport areas worldwide. In this paper, we explore the synthesis of these observations to provide a large-scale quantitative view of the mineralogical composition and its variability according to source region and time after transport.This work reveals that mineral dust in western Africa is a mixture of clays, quartz, iron and titanium oxides, representing at least 92 % of the dust mass. Calcite ranged between 0.3 and 8.4 % of the dust mass, depending on the origin. Our data do not show a systematic dependence of the dust mineralogical composition on origin; this is to be the case as, in most of the instances, the data represent the composition of the atmospheric burden after 1-2 days after emission, when air masses mix and give rise to a more uniform dust load. This has implications for the representation of the mineral dust composition in regional and global circulation models and in satellite retrievals.Iron oxides account for 58 ± 7 % of the mass of elemental Fe and for between 2 and 5 % of the dust mass. Most of them are composed of goethite, representing between 52 and 78 % of the iron oxide mass. We estimate that titanium oxides account for 1-2 % of the dust mass, depending on whether the dust is of Saharan or Sahelian origin.The mineralogical composition is a critical parameter for estimating the radiative and biogeochemical impact of mineral dust. The results regarding dust composition have been used to estimate the optical properties as well as the iron fractional solubility of Saharan and Sahelian dust.Data presented in this paper are provided in numerical form upon email request while they are being turned into a public database, the Dust-Mapped Archived Properties (DUST-MAP), which is an open repository for compositional data from other source regions in Africa and worldwide.

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Mineral dust aerosol net direct radiative effect during GERBILS field campaign period derived from SEVIRI and GERB

et al. 2014

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055 , and Geostationary Earth Radiation Budget (GERB) fluxes at the top of atmosphere are used to provide, for the first time, an observationally based estimate of the cloud-free net direct radiative effect (DRE) of mineral dust aerosol from geostationary satellite observations, providing new insights into the influence of time of day on the magnitude and sign of the shortwave, longwave, and overall net effect during sunlit hours. Focusing on the Geostationary Earth Radiation Budget Intercomparison of Longwave and Shortwave radiation (GERBILS) campaign over North Africa during June 2007, the presence of mineral dust aerosol reduces the outgoing longwave radiation at all times of day with the peak reduction clearly following the diurnal cycle of surface temperature. The instantaneous shortwave DRE shows strong dependencies on pristine sky albedo and solar zenith angle such that the same dust loading can induce a positive or negative value dependent on time of day. However, the area mean net DRE over the GERBILS period is dominated by the longwave component at all sampled times of day, with mineral dust inducing a reduction in outgoing net flux of the order of 10 W m −2 . Hence, in the mean sense, Saharan dust is found to warm the Earth-atmosphere system over northern Africa and the Middle East.

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Motivation, rationale and key results from the GERBILS Saharan dust measurement campaign

Cited by 62 publications

References 51 publications

Aerosol's optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study

Aerosol's optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study

Mapping the physico-chemical properties of mineral dust in western Africa: mineralogical composition

Mineral dust aerosol net direct radiative effect during GERBILS field campaign period derived from SEVIRI and GERB

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