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Title: Derivation of an observation-based map of North African dust emission

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Journal Article: Publisher's Accepted Manuscript
Journal Name:
Aeolian Research
Additional Journal Information:
Journal Volume: 16; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-05-16 09:23:12; Journal ID: ISSN 1875-9637
Country of Publication:
Country unknown/Code not available

Citation Formats

Evan, Amato T., Fiedler, Stephanie, Zhao, Chun, Menut, Laurent, Schepanski, Kerstin, Flamant, Cyrille, and Doherty, Owen. Derivation of an observation-based map of North African dust emission. Country unknown/Code not available: N. p., 2015. Web. doi:10.1016/j.aeolia.2015.01.001.
Evan, Amato T., Fiedler, Stephanie, Zhao, Chun, Menut, Laurent, Schepanski, Kerstin, Flamant, Cyrille, & Doherty, Owen. Derivation of an observation-based map of North African dust emission. Country unknown/Code not available. doi:10.1016/j.aeolia.2015.01.001.
Evan, Amato T., Fiedler, Stephanie, Zhao, Chun, Menut, Laurent, Schepanski, Kerstin, Flamant, Cyrille, and Doherty, Owen. 2015. "Derivation of an observation-based map of North African dust emission". Country unknown/Code not available. doi:10.1016/j.aeolia.2015.01.001.
title = {Derivation of an observation-based map of North African dust emission},
author = {Evan, Amato T. and Fiedler, Stephanie and Zhao, Chun and Menut, Laurent and Schepanski, Kerstin and Flamant, Cyrille and Doherty, Owen},
abstractNote = {},
doi = {10.1016/j.aeolia.2015.01.001},
journal = {Aeolian Research},
number = C,
volume = 16,
place = {Country unknown/Code not available},
year = 2015,
month = 3

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.aeolia.2015.01.001

Citation Metrics:
Cited by: 16works
Citation information provided by
Web of Science

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  • Changes in the emission, transport and deposition of aeolian dust have profound effects on regional climate, so that characterizing the lifecycle of dust in observations and improving the representation of dust in global climate models is necessary. A fundamental aspect of characterizing the dust cycle is quantifying surface dust fluxes, yet no spatially explicit estimates of this flux exist for the World’s major source regions. Here we present a novel technique for creating a map of the annual mean emitted dust flux for North Africa based on retrievals of dust storm frequency from the Meteosat Second Generation Spinning Enhanced Visiblemore » and InfraRed Imager (SEVIRI) and the relationship between dust storm frequency and emitted mass flux derived from the output of five models that simulate dust. Our results suggest that 64 (±16)% of all dust emitted from North Africa is from the Bodélé depression, and that 13 (±3)% of the North African dust flux is from a depression lying in the lee of the Aïr and Hoggar Mountains, making this area the second most important region of emission within North Africa.« less
  • This study uses a century length pre-industrial climate simulation by the Community Earth System Model (CESM 1.0) to explore statistical relationships between dust, clouds and atmospheric circulation, and to suggest a dynamical, rather than microphysical, mechanism linking subtropical North Atlantic lower tropospheric cloud cover with North African dust transport. The length of the run allows us to account for interannual variability of dust emissions and transport downstream of North Africa in the model. CESM’s mean climatology and probability distribution of aerosol optical depth in this region agrees well with available AERONET observations. In addition, CESM shows strong seasonal cycles ofmore » dust burden and lower tropospheric cloud fraction, with maximum values occurring during boreal summer, when a strong correlation between these two variables exists downstream of North Africa over the subtropical North Atlantic. Calculations of Estimated Inversion Strength (EIS) and composites of EIS on high and low downstream North Africa dust months during boreal summer reveal that dust is likely increasing inversion strength over this region due to both solar absorption and reflection. We find no evidence for a microphysical link between dust and lower tropospheric clouds in this region. These results yield new insight over an extensive period of time into the complex relationship between North African dust and lower tropospheric clouds over the open ocean, which has previously been hindered by spatiotemporal constraints of observations. Our findings lay a framework for future analyses using sub-monthly data over regions with different underlying dynamics.« less
  • Iron is an essential nutrient for phytoplankton. Although iron-containing dust mobilized from arid regions supplies the majority of the iron to the oceans, the key flux in terms of the biogeochemical response to atmospheric deposition is the amount of soluble or bioavailable iron. Atmospheric processing of mineral aerosols by anthropogenic pollutants (e.g. sulfuric acid) may transform insoluble iron into soluble forms. Previous studies have suggested higher iron solubility in smaller particles, as they are subject to more thorough atmospheric processing due to a longer residence time than coarse particles. On the other hand, the specific mineralogy of iron in dustmore » may also influence the particulate iron solubility in size. Compared to mineral dust aerosols, iron from combustion sources could be more soluble, and found more frequently in smaller particles. Internal mixing of alkaline dust with iron-containing minerals could significantly reduce iron dissolution in large dust aerosols due to the buffering effect, which may, in contrast, yield higher solubility in smaller particles externally mixed with alkaline dust (Ito and Feng, 2010). Here, we extend the modeling study of Ito and Feng (2010) to investigate atmospheric processing of mineral aerosols from African dust. In contrast to Asian dust, we used a slower dissolution rate for African dust in the fine mode. We compare simulated fractional iron solubility with observations. The inclusion of alkaline compounds in aqueous chemistry substantially limits the iron dissolution during long-range transport to the Atlantic Ocean: only a small fraction of iron (<0.2%) dissolves from illite in coarsemode dust aerosols with 0.45% soluble iron initially. In contrast, a significant fraction (1-1.5%) dissolves in fine-mode dust aerosols due to the acid mobilization of the iron-containing minerals externally mixed with carbonate minerals. Consequently, the model generally reproduces higher iron solubility in smaller particles as suggested by measurements over the Atlantic Ocean. Our results imply that the dissolution of iron in African dust is generally slower than that in Asian dust. Conventionally, dust is assumed as the major supply of bioavailable iron with a constant solubility at 1-2% to the remote ocean. Therefore, the timing and location of the atmospheric iron input to the ocean with detailed modeling of atmospheric processing could be different from those previously assumed. Past and future changes in aerosol supply of bioavailable iron might play a greater role in the nutrient supply for phytoplankton production in the upper ocean, as global warming has been predicted to intensify stratification and reduce vertical mixing from the deep ocean. Thus the feedback of climate change through ocean uptake of carbon dioxide as well as via aerosol-cloud interaction might be modified by the inclusion of iron chemistry in the atmosphere.« less
  • The productivity of the Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of long-range transported African dust is recognized as a potentially important but poorly quantified source of phosphorus. This study provides a first multiyear satellite-based estimate of dust deposition into the Amazon Basin using three dimensional (3D) aerosol measurements over 2007-2013 from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The 7-year average of dust deposition into the Amazon Basin is estimated to be 28 (8~48) Tg a -1 or 29 (8~50) kg ha -1 a -1. The dust deposition shows significant interannual variationmore » that is negatively correlated with the prior-year rainfall in the Sahel. The CALIOP-based multi-year mean estimate of dust deposition matches better with estimates from in-situ measurements and model simulations than a previous satellite-based estimate does. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3D nature of CALIOP aerosol measurements. The imported dust could provide about 0.022 (0.006~0.037) Tg P of phosphorus per year, equivalent to 23 (7~39) g P ha -1 a -1 to fertilize the Amazon rainforest. This out-of-Basin P input is comparable to the hydrological loss of P from the Basin, suggesting an important role of African dust in preventing phosphorus depletion on time scales of decades to centuries.« less