Direct and indirect impacts of Saharan dust acting as cloud condensation nuclei on tropical cyclone eyewall development

Zhang, Henian; McFarquhar, Greg M.; Cotton, William R.; Deng, Yi

doi:10.1029/2009gl037276

Cited by 54 publications

(69 citation statements)

References 16 publications

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“…The centers of all grids and that of the storm were approximately coincident (∼15 • N, 40 • W). The corresponding time steps were 60, 20, and 2.5 s. The idealized TC simulations were similar to those of Zhang et al (2007Zhang et al ( , 2009) except for recent updates in the model. For this study we implemented a prognostic scheme (based on the O' Dowd diagnostic formulae (1997) to take into account sea-spray sources for the film, jet, and spume modes which act as CCN and GCCN, respectively.…”

Section: Model Configuration and Experimental Designsupporting

confidence: 54%

“…For instance, other mechanisms could be preventing a rapid intensification of the storm provided the simulated invigoration of convective activity in the outer rainbands (see Bister, 1997Bister, , 2001). Sublimation of ice crystals could also be playing a non negligible role; however, Zhang et al (2007Zhang et al ( , 2009) performed a heating analysis that led to the conclusion that the main response was at low-levels. Riemer et al (2010) also finds evidence that the invigoration of convective activity in the outer rainbands leads to a reduction in TC intensity.…”

Section: Discussionmentioning

confidence: 99%

“…The latter two examined the impacts of dust acting as CCN. Zhang et al (2009) revealed a nonmonotonic response such that increases in CCN concentrations weakened the storm, while further increases in CCN concentrations either strengthened or had no impact, and further increases led to a decrease in storm intensity. That study did not reveal why such peculiar behavior should occur.…”

Section: Introductionmentioning

confidence: 99%

“…Several studies such as Khain et al (2008Khain et al ( , 2010 and Zhang et al (2007Zhang et al ( , 2009) specifically focused on aerosol effects on hurricanes. The latter two examined the impacts of dust acting as CCN.…”

Section: Introductionmentioning

confidence: 99%

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Investigations of aerosol impacts on hurricanes: virtual seeding flights

Carrió

Cotton

2011

Atmos. Chem. Phys.

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Abstract. This paper examines the feasibility of mitigating the intensity of hurricanes by enhancing the CCN concentrations in the outer rainband region. Increasing CCN concentrations would cause a reduced collision and coalescence, resulting in more supercooled liquid water to be transported aloft which then freezes and enhances convection via enhanced latent heat of freezing. The intensified convection would condense more water ultimately enhancing precipitation in the outer rainbands. Enhanced evaporative cooling from the increased precipitation in the outer rainbands would produce stronger and more widespread areal cold pools which block the flow of energy into the storm core, ultimately inhibiting the intensification of the tropical cyclone.We designed a series of multi-grid for which the time of the "virtual flights" as well as the aerosol release rates are varied. A code that simulates the flight of a plane is used to increase the CCN concentrations as an aircraft flies. Results show a significant sensitivity to both the seeding time and the aerosol release rates and support the aforementioned hypothesis.

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Section: Model Configuration and Experimental Designsupporting

confidence: 54%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Investigations of aerosol impacts on hurricanes: virtual seeding flights

Carrió

Cotton

2011

Atmos. Chem. Phys.

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“…Zhang et al (2007) found that dust could act as CCN and induce changes in the hydrometeor properties, modifying the latent heat distribution and ultimately influencing the storm intensity through complex dynamical processes. In a more recent work, Zhang et al (2009) showed that dust could indirectly affect the eyewall development by modifying the latent heat release in rainbands. Both studies note that more detailed observational information on Saharan dust microphysical properties and vertical distributions is needed to further develop a mechanistic understanding of the potential effects of dust on hurricane genesis and intensity.…”

mentioning

confidence: 99%

Observations of Saharan dust microphysical and optical properties from the Eastern Atlantic during NAMMA airborne field campaign

et al. 2011

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Abstract. As part of the international project entitled "African Monsoon Multidisciplinary Analysis (AMMA)", NAMMA (NASA AMMA) aimed to gain a better understanding of the relationship between the African Easterly Waves (AEWs), the Sahara Air Layer (SAL), and tropical cyclogenesis. The NAMMA airborne field campaign was based out of the Cape Verde Islands during the peak of the hurricane season, i.e., August and September 2006. Multiple Sahara dust layers were sampled during 62 encounters in the eastern portion of the hurricane main development region, covering both the eastern North Atlantic Ocean and the western Saharan desert (i.e., 5-22 • N and 10-35 • W). The centers of these layers were located at altitudes between 1.5 and 3.3 km and the layer thickness ranged from 0.5 to 3 km. Detailed dust microphysical and optical properties were characterized using a suite of in-situ instruments aboard the NASA DC-8 that included a particle counter, an Ultra-High Sensitivity Aerosol Spectrometer, an Aerodynamic Particle Sizer, a nephelometer, and a Particle Soot Absorption Photometer. The NAAMA sampling inlet has a size cut (i.e., 50% transmission efficiency size) of approximately 4 µm in diameter for dust particles, which limits the representativeness of the NAMMA observational findings. The NAMMA dust observations showed relatively low particle number densities, Correspondence to: G. Chen (gao.chen@nasa.gov) ranging from 268 to 461 cm −3 , but highly elevated volume density with an average at 45 µm 3 cm −3 . NAMMA dust particle size distributions can be well represented by tri-modal lognormal regressions. The estimated volume median diameter (VMD) is averaged at 2.1 µm with a small range of variation regardless of the vertical and geographical sampling locations. TheÅngström Exponent assessments exhibited strong wavelength dependence for absorption but a weak one for scattering. The single scattering albedo was estimated at 0.97 ± 0.02. The imaginary part of the refractive index for Sahara dust was estimated at 0.0022, with a range from 0.0015 to 0.0044. Closure analysis showed that observed scattering coefficients are highly correlated with those calculated from spherical Mie-Theory and observed dust particle size distributions. These values are generally consistent with literature values reported from studies with similar particle sampling size range.

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Global observations of aerosol-cloud-precipitation-climate interactions

et al. 2014

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Cloud drop condensation nuclei (CCN) and ice nuclei (IN) particles determine to a large extent cloud microstructure and, consequently, cloud albedo and the dynamic response of clouds to aerosol-induced changes to precipitation. This can modify the reflected solar radiation and the thermal radiation emitted to space. Measurements of tropospheric CCN and IN over large areas have not been possible and can be only roughly approximated from satellite-sensor-based estimates of optical properties of aerosols. Our lack of ability to measure both CCN and cloud updrafts precludes disentangling the effects of meteorology from those of aerosols and represents the largest component in our uncertainty in anthropogenic climate forcing. Ways to improve the retrieval accuracy include multiangle and multipolarimetric passive measurements of the optical signal and multispectral lidar polarimetric measurements. Indirect methods include proxies of trace gases, as retrieved by hyperspectral sensors. Perhaps the most promising emerging direction is retrieving the CCN properties by simultaneously retrieving convective cloud drop number concentrations and updraft speeds, which amounts to using clouds as natural CCN chambers. These satellite observations have to be constrained by in situ observations of aerosol-cloud-precipitation-climate (ACPC) interactions, which in turn constrain a hierarchy of model simulations of ACPC. Since the essence of a general circulation model is an accurate quantification of the energy and mass fluxes in all forms between the surface, atmosphere and outer space, a route to progress is proposed here in the form of a series of box flux closure experiments in the various climate regimes. A roadmap is provided for quantifying the ACPC interactions and thereby reducing the uncertainty in anthropogenic climate forcing.

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Direct and indirect impacts of Saharan dust acting as cloud condensation nuclei on tropical cyclone eyewall development

Cited by 54 publications

References 16 publications

Investigations of aerosol impacts on hurricanes: virtual seeding flights

Investigations of aerosol impacts on hurricanes: virtual seeding flights

Observations of Saharan dust microphysical and optical properties from the Eastern Atlantic during NAMMA airborne field campaign

Global observations of aerosol-cloud-precipitation-climate interactions

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