Ship trails and ship induced cloud dynamics

Porch, W.M.; Kao, Chih-Yue Jim; Kelley, R.G.

doi:10.1016/0960-1686(90)90073-v

Cited by 14 publications

(10 citation statements)

References 11 publications

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“…It has been suggested that perturbations other than increased CCN concentrations might be involved in the formation and maintenance of ship tracks. Other possible perturbations include heat from ships [Porch et al, 1990] and air wake vortices behind ships [Hindman, 1990]. However, we will confine our attention to the effects of CCN injections on warm, stratiform clouds in the marine boundary layer.…”

mentioning

confidence: 92%

Numerical modeling of ship tracks produced by injections of cloud condensation nuclei into marine stratiform clouds

Ackerman¹,

Toon²,

Hobbs³

1995

J. Geophys. Res.

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Ship tracks are long-lived, linear regions of enhanced reflectivity in low-lying marine clouds that appear in satellite imagery downwind of ships. Ship tracks were first observed as cloud lines in visible satellite imagery (type 1). A second (and more common) type of ship track (type 2), which is masked at visible wavelengths by natural variability in cloud reflectivity, is seen at near-infrared wavelengths in satellite imagery. A one-dimensional numerical model is used to simulate measurements of both types of ship tracks and to investigate interactions between aerosol and cloud microphysics, radiative transfer, and turbulent mixing in the cloud-topped marine boundary layer that lead to the formation and provide for the persistence of ship tracks. We find that cloud condensation nuclei (CCN) injections can account for many of the observed properties of ship tracks. Higher CCN concentrations produce increased droplet concentrations, which enhance cloud reflectivity by reducing droplet radius and increasing droplet cross-sectional area. The smaller droplets also reduce the drizzle rate, which can allow cloud water to increase under some conditions, thereby leading to higher cloud reflectivity. However, smaller droplets also evaporate more readily below cloud base. Increased evaporation reduces mixing between the cloud and the subcloud layers during daytime, which causes a decrease in cloud water. The distinction between the two types of ship tracks is suggested to be due to differences in ambient concentrations of CCN that cause variations in turbulent mixing in the boundary layer, through the effect of cloud droplet concentrations on cloud-top longwave radiative cooling. The model predicts lifetimes of > 1 day and > 2 days for the simulated type 1 and type 2 ship tracks, respectively. In the atmosphere, processes not treated in the model, such as horizontal dispersion and changes in large-scale atmospheric conditions, may limit ship track lifetimes. 1. Introduction Ship tracks are long-lived, linear regions of enhanced solar reflectivity in marine stratiform clouds that appear in satellite imagery downwind of ships. They were first reported as "anomalous cloud lines" in visible satellite imagery [Conover, 1966]. The cloud cover in the regions in which the features were observed ranged from apparently cloud-free to overcast, where the lines became indiscernible. Conover concluded that the cloud lines were low-lying water clouds, resulting from the addition of CCN present in ship exhausts under special meteorological conditions; Bowley [1967] observed that these cloud lines were typically associated with fog in a shallow boundary layer. Conover suggested that the ambient air in which ship tracks form must have very low concentrations of CCN; Twomey et al. [1968] reported that very low CCN concentrations (< 5 cm '3) are sometimes measured in areas where ship tracks occur. Using multiple Paper number 95JD00026. 0148-0227/95/95JD-00026505.00 wavelength detectors on modern satellites, Coakley et al. [1987] expanded the...

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mentioning

confidence: 92%

Numerical modeling of ship tracks produced by injections of cloud condensation nuclei into marine stratiform clouds

Ackerman¹,

Toon²,

Hobbs³

1995

J. Geophys. Res.

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“…In addition, global ship traffic is increasing at a rate of about 8% per year, and continued growth is projected with the globalization of world markets [U.S. Department of Transportation, 1988].Shipping lanes still, for the most part, follow fairly narrow corridors along trade wind routes. Within these corridors, ship trails (plumes) can remain relatively well defined over distances of several hundred kilometers[Porch et al, 1990]. The anthropogenic emissions from these multimegawatt (tens to hundreds of megawatts) mobile power plants may provide a locally potent source of NO x to remote and otherwise pristine oceanic regions.…”

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confidence: 99%

Summertime tropospheric observations related to N_x O_y distributions and partitioning over Alaska: Arctic Boundary Layer Expedition 3A

Sandholm¹,

Bradshaw²,

Chen³

et al. 1992

J. Geophys. Res.

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Measurements of the reactive odd nitrogen compounds NO, NO2, peroxyacetyl nitrate (PAN), and NOy are presented for the summertime middle/lower troposphere (6.1–0.15 km) over northern high latitudes. In addition, the chemical signatures revealed from concurrent measurements of O3, CO, C2H2, C2H6, C3H8, C2Cl4, and H2O are used to further characterize factors affecting the budget and distribution of NxOy, in the Arctic and sub‐Arctic tropospheric air masses sampled over Alaska during the NASA Arctic Boundary Layer Expedition (ABLE 3A) field campaign. Many of the compounds listed above exhibited a general trend of median mixing ratios increasing in proportion with altitude within the lower 6‐km column. However, median mixing ratios of NO and NOx (NO + NO2) were nearly independent of altitude, having values of about 8.5 and 25 pptv, respectively. Median mixing ratios of NOy varied from about 350 pptv within the lowest altitudes to about 600 pptv within the highest altitudes sampled. PAN constituted the largest fraction of NOy (∼50%) at the highest altitudes. In addition, PAN mixing ratios accounted for all of the approximate 60 pptv/km altitudinal dependency in NOy. The analyses presented implicate biomass burning in Siberia as the probable source of about one‐third of the NOy abundance within the middle/lower troposphere over Alaska. These analyses also implicate the downward transport of air from altitudes in the vicinity of the tropopause as a major contributor to the abundance of NOy, (∼30–50%) within the lower 6‐km column over Alaska. However, the exact origin of this high‐altitude NOy remains uncertain. The impact of lower latitude industrial/urban pollution also remains largely uncertain, although various chemical signatures imply inputs from these regions would have been relatively well aged (15–30 days).

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“…Essa estabilidade inibe a mistura vertical necessária para manter os estratos-cúmulos marinhos, limitando o transporte de água da superfície para a camada de nuvem e fazendo com que a nuvem entre em colapso. A partir da análise de fotografias obtidas a bordo da nave Apollo-Soyuz (14 m de resolução), Porch et al (1990) observam que a trajetória do navio aparece inicialmente apenas como uma faixa de maior brilho das nuvens estratos-cúmulos já existentes e eventualmente crescendo para uma estrutura independente cercada por regiões claras em ambos os lados, indicando que os fluxos de calor e umidade oriundos dos navios contribuem para um aumento na intensidade dos movimentos ascendentes e descendentes associado à circulação das nuvens. Esse desenvolvimento de uma nova estrutura de nuvens ao longo da trajetória e o fato de que a intersecção de duas trajetórias não apresenta maior brilho que as trajetórias individuais é um forte argumento contra a relação direta entre refletividade das nuvens e concentração de CCN, ainda segundo Porch et al (1990).…”

Section: Ambiente Marítimounclassified

“…Usando condições meteorológicas iniciais semelhantes àquelas medidas nas trajetórias dos navios, Porch et al (1990) fizeram uso de um modelo hidrodinâmico de nuvens para tentar reproduzir as características observadas nas trajetórias dos navios. Os resultados indicaram que o empuxo fornecido pelo calor liberado pelo navio pode ser tão importante quanto à energia liberada no processo de condensação.…”

Section: Experimentação Numérica Sobre Os Efeitos Dos Aerossóis Na Prunclassified

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"Efeito dos núcleos de condensação na formação de nuvens e o desenvolvimento da precipitação na região amazônica durante a estação seca"

Martins¹,

Gonçalves²

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Primeiramente quero expressar minha inestimável gratidão aos meus orientadores, Dr. Fábio Luiz Teixeira Gonçalves e Dra Maria Assunção Faus da Silva Dias, pela oportunidade de realização deste projeto em uma área de pesquisa tão vislumbrante, as ciências atmosféricas, e em um tema tão intrigante, o efeito das atividades humanas no desenvolvimento da precipitação. Agradeço a todos os docentes e técnicos da Universidade Federal Tecnológica do Paraná, que de alguma forma contribuíram para o afastamento de minhas atividades docentes naquela instituição. Agradeço em especial aos

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Ship trails and ship induced cloud dynamics

Cited by 14 publications

References 11 publications

Numerical modeling of ship tracks produced by injections of cloud condensation nuclei into marine stratiform clouds

Numerical modeling of ship tracks produced by injections of cloud condensation nuclei into marine stratiform clouds

Summertime tropospheric observations related to N_x O_y distributions and partitioning over Alaska: Arctic Boundary Layer Expedition 3A

"Efeito dos núcleos de condensação na formação de nuvens e o desenvolvimento da precipitação na região amazônica durante a estação seca"

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Ship trails and ship induced cloud dynamics

Cited by 14 publications

References 11 publications

Numerical modeling of ship tracks produced by injections of cloud condensation nuclei into marine stratiform clouds

Numerical modeling of ship tracks produced by injections of cloud condensation nuclei into marine stratiform clouds

Summertime tropospheric observations related to Nx Oy distributions and partitioning over Alaska: Arctic Boundary Layer Expedition 3A

"Efeito dos núcleos de condensação na formação de nuvens e o desenvolvimento da precipitação na região amazônica durante a estação seca"

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Summertime tropospheric observations related to N_x O_y distributions and partitioning over Alaska: Arctic Boundary Layer Expedition 3A