Measurements of ship‐induced tracks in clouds off the Washington coast

Ferek, Ronald J.; Hegg, D́ean A.; Hobbs, Peter V.; Durkee, Philip A.; Nielsen, K.

doi:10.1029/98jd02121

Cited by 63 publications

(52 citation statements)

References 12 publications

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“…Also, numerous smaller droplets in ship tracks is predicted to lead to less efficient coalescence and a slightly lower cloud base precipitation rate, following Albrecht (1989). Such a response has been observed in previous field studies (e.g., Ferek et al, 1998;Lu et al, 2007).…”

Section: Cloud Response In Ship Tracks: In Situ Observationsmentioning

confidence: 50%

“…There have been a number of observational studies of ship tracks, including in-situ airborne measurements (e.g., Radke et al, 1989;Ferek et al, 1998;Durkee et al, 2000;Twohy et al, 2005;Lu et al, 2007Lu et al, , 2009 and remote sensing satellite observations (e.g., Coakley and Walsh, 2002;Schreier et al, 2007;Segrin et al, 2007;Lebsock et al, 2008;Stephens, 2011, 2012). Whereas ample evidence exists that increased aerosol levels lead to more numerous and smaller cloud droplets, the response of cloud macrophysics (i.e., cloud thickness, LWP) to aerosol perturbations is not as clear-cut.…”

Section: Introductionmentioning

confidence: 99%

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Occurrence of lower cloud albedo in ship tracks

et al. 2012

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Abstract. The concept of geoengineering by marine cloud brightening is based on seeding marine stratocumulus clouds with sub-micrometer sea-salt particles to enhance the cloud droplet number concentration and cloud albedo, thereby producing a climate cooling effect. The efficacy of this as a strategy for global cooling rests on the extent to which aerosolperturbed marine clouds will respond with increased albedo. Ship tracks, quasi-linear cloud features prevalent in oceanic regions impacted by ship exhaust, are a well-known manifestation of the effect of aerosol injection on marine clouds. We present here an analysis of the albedo responses in ship tracks, based on in situ aircraft measurements and three years of satellite observations of 589 individual ship tracks. It is found that the sign (increase or decrease) and magnitude of the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. In a closed cell structure (cloud cells ringed by a perimeter of clear air), nearly 30 % of ship tracks exhibited a decreased albedo. Detailed cloud responses must be accounted for in global studies of the potential efficacy of sea-spray geoengineering as a means to counteract global warming.

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Section: Cloud Response In Ship Tracks: In Situ Observationsmentioning

confidence: 50%

Section: Introductionmentioning

confidence: 99%

Occurrence of lower cloud albedo in ship tracks

et al. 2012

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“…The observed increase in cloud droplet number concentration ranges between 40 cm −3 and 800 cm −3 (McComiskey et al, 2009), though most observed cloud droplet number concentrations lie within a narrower range of 40 to 200 cm −3 (Ferek et al, 1998;Hobbs et al, 2000;Hudson et al, 2000;.…”

Section: Microphysical and Radiative Effectsmentioning

confidence: 99%

Real-case simulations of aerosol–cloud interactions in ship tracks over the Bay of Biscay

et al. 2015

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Abstract. Ship tracks provide an ideal test bed for studying aerosol-cloud interactions (ACIs) and for evaluating their representation in model parameterisations. Regional modelling can be of particular use for this task, as this approach provides sufficient resolution to resolve the structure of the produced track including their meteorological environment whilst relying on the same formulations of parameterisations as many general circulation models. In this work we simulate a particular case of ship tracks embedded in an optically thin stratus cloud sheet which was observed by a polar orbiting satellite at 12:00 UTC on 26 January 2003 around the Bay of Biscay.The simulations, which include moving ship emissions, show that the model is indeed able to capture the structure of the track at a horizontal grid spacing of 2 km and to qualitatively capture the observed cloud response in all simulations performed. At least a doubling of the cloud optical thickness was simulated in all simulations together with an increase in cloud droplet number concentration by about 40 cm −3 (300 %) and decrease in effective radius by about 5 µm (40 %). Furthermore, the ship emissions lead to an increase in liquid water path in at least 25 % of the track regions.We are confident in the model's ability to capture key processes of ship track formation. However, it was found that realistic ship emissions lead to unrealistic aerosol perturbations near the source regions within the simulated tracks due to grid-scale dilution and homogeneity.Combining the regional-modelling approach with comprehensive field studies could likely improve our understanding of the sensitivities and biases in ACI parameterisations, and could therefore help to constrain global ACI estimates, which strongly rely on these parameterisations.

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“…Previous ship plume studies have estimated the plume width and height at a plume age of 1 s to be approximately 10 and 5.5 m, respectively (von Glasow et al, 2003;Durkee et al, 2000a;Ferek et al, 1998), and we used these values for t 0 , w 0 and h 0 , respectively. The parameters α = 0.75 and β = 0.6 are the "best guesses" estimated from the expansion of ship tracks reported in the literature (von Glasow et al, 2003;Durkee et al, 2000a) and confirmed by observations reported in Petzold et al (2008).…”

Section: Model Treatment Of Dilutionmentioning

confidence: 99%

Modeling the evolution of aerosol particles in a ship plume using PartMC-MOSAIC

et al. 2014

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Abstract. This study investigates the evolution of shipemitted aerosol particles using the stochastic particleresolved model PartMC-MOSAIC (Particle Monte Carlo model-Model for Simulating Aerosol Interactions and Chemistry). Comparisons of our results with observations from the QUANTIFY (Quantifying the Climate Impact of Global and European Transport Systems) study in 2007 in the English Channel and the Gulf of Biscay showed that the model was able to reproduce the observed evolution of total number concentration and the vanishing of the nucleation mode consisting of sulfate particles. Further process analysis revealed that during the first hour after emission, dilution reduced the total number concentration by four orders of magnitude, while coagulation reduced it by an additional order of magnitude. Neglecting coagulation resulted in an overprediction of more than one order of magnitude in the number concentration of particles smaller than 40 nm at a plume age of 100 s. Coagulation also significantly altered the mixing state of the particles, leading to a continuum of internal mixtures of sulfate and black carbon. The impact on cloud condensation nuclei (CCN) concentrations depended on the supersaturation threshold S at which CCN activity was evaluated. For the base case conditions, characterized by a low formation rate of secondary aerosol species, neglecting coagulation, but simulating condensation, led to an underestimation of CCN concentrations of about 37 % for S = 0.3 % at the end of the 14-h simulation. In contrast, for supersaturations higher than 0.7 %, neglecting coagulation resulted in an overestimation of CCN concentration, about 75 % for S = 1 %. For S lower than 0.2 % the differences between simulations including coagulation and neglecting coagulation were negligible. Neglecting condensation, but simulating coagulation did not impact the CCN concentrations below 0.2 % and resulted in an underestimation of CCN concentrations for larger supersaturations, e.g., 18 % for S = 0.6 %. We also explored the role of nucleation for the CCN concentrations in the ship plume. For the base case the impact of nucleation on CCN concentrations was limited, but for a sensitivity case with higher formation rates of secondary aerosol over several hours, the CCN concentrations increased by an order of magnitude for supersaturation thresholds above 0.3 %.

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Measurements of ship‐induced tracks in clouds off the Washington coast

Cited by 63 publications

References 12 publications

Occurrence of lower cloud albedo in ship tracks

Occurrence of lower cloud albedo in ship tracks

Real-case simulations of aerosol–cloud interactions in ship tracks over the Bay of Biscay

Modeling the evolution of aerosol particles in a ship plume using PartMC-MOSAIC

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