Semidirect dynamical and radiative effect of North African dust transport on lower tropospheric clouds over the subtropical North Atlantic in CESM 1.0

DeFlorio, Michael J.; Ghan, Steven J.; Singh, Balwinder; Miller, Arthur J.; Cayan, Daniel R.; Russell, Lynn M.; Somerville, Richard C. J.

doi:10.1002/2013jd020997

Cited by 7 publications

(6 citation statements)

References 77 publications

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“…Dust aerosols not only affect the global climate system through their direct interactions with shortwave and longwave radiation but also through the modification of temperature and water vapor profiles, wind circulation, and cloud properties (Boucher et al, 2013;Knippertz and Stuut, 2014). Because mineral dust absorbs shortwave and longwave radiation, it can trigger uneven radiative heating or cooling within the atmosphere, which can locally alter clouds and precipitation distributions (Wong et al, 2009;DeFlorio et al, 2014;Doherty and Evan, 2014;Huang et al, 2014;Amiri-Farahani et al, 2017). Additionally, spatial variability in dust loading and absorption can drive mesoscale or synoptic-scale circulation, further influencing the cloud and precipitation distributions (Chen et al, 2010;Perlwitz and Miller, 2010).…”

Section: Impacts Of Coarse and Super-coarse Dust Absorption On Clouds...mentioning

confidence: 99%

A review of coarse mineral dust in the Earth system

Adebiyi¹,

Kok²,

Murray³

et al. 2022

Preprint

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Mineral dust particles suspended in the atmosphere span more than three orders of magnitude in diameter, from less than 0.1 µm to more than 100 µm. This wide size range makes dust a unique aerosol species with the ability to interact with many aspects of the Earth system, including radiation, clouds, hydrology, atmospheric chemistry, and biogeochemistry. This review focuses on coarse and super-coarse dust aerosols, which we respectively define as dust particles with a diameter between 2.5 - 10 µm and 10 - 62.5 µm. We review several lines of observational evidence indicating that coarse and super-coarse dust particles are transported farther than previously expected and that the abundance of these particles is substantially underestimated in current global models. We synthesize previous studies that used observations, theories, and model simulations to highlight the impacts of coarse and super-coarse dust aerosols on the Earth system, including their effects on dust-radiation interactions, dust-cloud interactions, and atmospheric chemistry, and biogeochemistry. In addition, we examine several limitations in the representation of coarse and super-coarse dust aerosols in current model simulations and in remote-sensing retrievals. Because these limitations substantially contribute to the uncertainties in simulating the abundance and impacts of coarse and super-coarse dust aerosols, we offer some recommendations to facilitate future studies. Overall, we conclude that an accurate representation of coarse and super-coarse properties is critical in understanding the overall impacts of dust aerosols on the Earth system.

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Section: Impacts Of Coarse and Super-coarse Dust Absorption On Clouds...mentioning

confidence: 99%

A review of coarse mineral dust in the Earth system

Adebiyi¹,

Kok²,

Murray³

et al. 2022

Preprint

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“…Today, African dust is known to be an important nutrient for the Amazon rainforest [e.g., Swap et al, 1992;Yu et al, 2015] and other marine and terrestrial ecosystems [e.g., Mahowald et al, 2005;Wang et al, 2012;Gross et al, 2015]. Saharan dust directly and indirectly affects global and regional climate by influencing the radiation budget [Mahowald et al, 2010;DeFlorio et al, 2014] and potentially impacts the frequency of tropical cyclones and hurricanes [Evan et al, 2006;Bretl et al, 2015]. It is also an important source of ice nuclei in the Amazon Basin during the wet season [Prenni et al, 2009].…”

Section: Introductionmentioning

confidence: 99%

The transatlantic dust transport from North Africa to the Americas—Its characteristics and source regions

et al. 2015

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Transport of Saharan dust over the Atlantic to the Americas is a relevant process since dust is a nutrient for marine and terrestrial ecosystems. It is therefore important to better quantify the frequency and amount of transatlantic dust transport, its preferred altitude and duration, and the regions of dust origin. This study uses a novel combination of Eulerian and Lagrangian diagnostics, applied to a previously validated 5 year simulation of the fifth generation European Centre for Medium Range Weather Forecast‐Hamburg‐model (ECHAM5)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry model, to quantify these dust transport characteristics and their seasonal variations. Results confirm the previously found preferred transatlantic dust pathways: in boreal winter and spring, African dust is mainly transported below 800 hPa toward South America, whereas in summer and autumn the preferred pathway is to the Caribbean and occurs in a layer up to 500 hPa. The averaged transport duration from dust emission to deposition is 10 days in winter for deposition in the Amazon region and almost 12 days in summer for deposition in the Caribbean. These estimates were obtained by combining correlation analyses of Eulerian dust fluxes and trajectory calculations. The latter were also essential to identify the main source regions of transatlantic dust transport, which were found in all seasons in northwestern Africa (Algeria, Mali, and Mauritania) but not farther east, e.g., in the Bodélé Depression. A specific Lagrangian analysis for this dust emission hot spot suggests that wet deposition associated with the Intertropical Convergence Zone in winter and the African monsoon in summer inhibits Bodélé dust to leave the African continent.

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“…In warm clouds, increased dustiness was found to slightly enhance cloud droplet concentrations, with an ensuing small cooling around and near North African deserts, and the opposite case for decreased dustiness. Our simulations show the opposite semidirect effects as observations over the tropical North Atlantic just west of Africa (Amiri-Farahani et al, 2017;Doherty & Evan, 2014) and a modeling study (DeFlorio et al, 2014). This may be linked to our use of fixed SSTs, which prohibited the ocean surface from cooling in response to overhead dust blocking sunlight.…”

Section: Discussionmentioning

confidence: 46%

“…Our simulations show the opposite semidirect effects as observations over the tropical North Atlantic just west of Africa (Amiri-Farahani et al, 2017;Doherty & Evan, 2014) and a modeling study (DeFlorio et al, 2014). This may be linked to our use of fixed SSTs, which prohibited the ocean surface from cooling in response to overhead dust blocking sunlight.…”

Section: Discussionmentioning

confidence: 46%

Global Radiative Impacts of Mineral Dust Perturbations Through Stratiform Clouds

et al. 2020

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Airborne mineral dust influences cloud occurrence and optical properties, which may provide a pathway for recent and future changes in dust concentration to alter the temperature at Earth's surface. However, despite prior suggestions that dust‐cloud interactions are an important control on the Earth's radiation balance, we find global mean cloud radiative effects to be insensitive to widespread dust changes. Here we simulate uniformly applied shifts in dust amount in a present‐day atmosphere using a version of the CAM5 atmosphere model (within CESM v1.2.2) modified to incorporate laboratory‐based ice nucleation parameterizations in stratiform clouds. Increasing and decreasing dustiness from current levels to paleoclimate extremes caused effective radiative forcings through clouds of +0.02 ± 0.01 and −0.05 ± 0.02 W/m2, respectively, with ranges of −0.26 to +0.13 W/m2 and −0.21 to +0.39 W/m2 from sensitivity tests. Our simulations suggest that these forcings are limited by several factors. Longwave and shortwave impacts largely cancel, particularly in mixed‐phase clouds, while in warm and cirrus clouds opposite responses between regions further reduce each global forcing. Additionally, changes in dustiness cause opposite forcings through aerosol indirect effects in mixed‐phase clouds as in cirrus, while in warm clouds indirect effects are weak at nearly all locations. Nevertheless, regional forcings and global impacts on longwave and shortwave radiation were found to be nonnegligible, suggesting that cloud‐mediated dust effects have significance in simulations of present and future climate.

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Semidirect dynamical and radiative effect of North African dust transport on lower tropospheric clouds over the subtropical North Atlantic in CESM 1.0

Cited by 7 publications

References 77 publications

A review of coarse mineral dust in the Earth system

A review of coarse mineral dust in the Earth system

The transatlantic dust transport from North Africa to the Americas—Its characteristics and source regions

Global Radiative Impacts of Mineral Dust Perturbations Through Stratiform Clouds

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