Composite Ship Track Characteristics

Durkee, Philip A.; Chartier, R. E.; Brown, Andrew R.; Trehubenko, Eric J.; Rogerson, S. D.; Skupniewicz, C. E.; Nielsen, K.; Platnick, S.; King, Michael D.

doi:10.1175/1520-0469(2000)057<2542:cstc>2.0.co;2

Cited by 84 publications

(85 citation statements)

References 14 publications

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“…For a pixel to be classified as low cloud, a temperature threshold was used. Durkee et al (2000b) present measurements of the height of low stratiform clouds which are modified by ship emissions. The cloud top height never exceeded 1500 m in these measurements.…”

Section: Ship Track Mask Algorithmmentioning

confidence: 99%

Impact of ship emissions on the microphysical, optical and radiative properties of marine stratus: a case study

Schreier

Kokhanovsky²,

Eyring³

et al. 2006

Atmos. Chem. Phys.

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Abstract. Modifications of existing clouds by the exhaust of ships are well-known but inadequately quantified impacts, which could contribute to climate change. The perturbation of a cloud layer by ship-generated aerosol changes the cloud reflectivity and is identified by long curves in satellite images, known as ship tracks. As ship tracks indicate a pollution of a very clean marine environment and also affect the radiation budget below and above the cloud, it is important to investigate their radiative and climatic effects. Satellitedata from MODIS on Terra are used to examine a scene from 10 February 2003 where ship tracks were detected close to the North American West-Coast. The cloud optical and microphysical properties are derived using a semi-analytical retrieval technique combined with a look-up-table approach. An algorithm is presented to distinguish ship-track-pixels from the unperturbed cloud pixels in the scene and from this the optical properties of the former are compared to those of the latter. Within the ship tracks a significant change in the droplet number concentration, the effective radius and the optical thickness are found compared to the unaffected cloud. The resulting cloud properties are used to calculate the radiation budget below and above the cloud. Assuming a mean solar zenith angle of 63 • for the selected scene, the mean solar surface radiation below the ship track is decreased by 43.2 Wm −2 and the mean reflectance at top of atmosphere (TOA) is increased by 40.8 Wm −2 . For the entire analyzed scene the ship emission decreases the solar radiation at the surface by 2.1 Wm −2 and increases the backscattered solar radiation at TOA by 2.0 Wm −2 , whereas no significant effect on thermal radiation was detected.

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Section: Ship Track Mask Algorithmmentioning

confidence: 99%

Impact of ship emissions on the microphysical, optical and radiative properties of marine stratus: a case study

Schreier

Kokhanovsky²,

Eyring³

et al. 2006

Atmos. Chem. Phys.

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“…See the footnotes for details on the single cases. Durkee et al (2000a) discuss a case of vertical plume dilution where first bright clouds (indicative of the ship pollution reaching the top of the MBL) appear about 1400 s after plume release in a 400 m deep MBL. Based on this, our "best guess" for β is 0.6.…”

Section: Model Descriptionmentioning

confidence: 99%

“…This leads to a chemical lifetime of about 2 days. Note that the mean lifetime of 7.3 h that was derived during the MAST campaign (Durkee et al, 2000a) is based on a different definition, namely on cloud albedo effects as measured from satellites. The most dramatic reductions in pollutant concentrations of course occur during the first hour after plume release.…”

Section: Effects Of Emissions Of a Single Shipmentioning

confidence: 99%

Modeling the chemical effects of ship exhaust in the cloud-free marine boundary layer

Glasow

Lawrence²,

Sander³

et al. 2003

Atmos. Chem. Phys.

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Abstract. The chemical evolution of the exhaust plumes of ocean-going ships in the cloud-free marine boundary layer is examined with a box model. Dilution of the ship plume via entrainment of background air was treated as in studies of aircraft emissions and was found to be a very important process that significantly alters model results. We estimated the chemical lifetime (defined as the time when differences between plume and background air are reduced to 5% or less) of the exhaust plume of a single ship to be 2 days. Increased concentrations of NO x (= NO + NO 2 ) in the plume air lead to higher catalytical photochemical production rates of O 3 and also of OH. Due to increased OH concentrations in the plume, the lifetime of many species (especially NO x ) is significantly reduced in plume air. The chemistry on background aerosols has a significant effect on gas phase chemistry in the ship plume, while partly soluble shipproduced aerosols are computed to only have a very small effect. Soot particles emitted by ships showed no effect on gas phase chemistry. Halogen species that are released from sea salt aerosols are slightly increased in plume air. In the early plume stages, however, the mixing ratio of BrO is decreased because it reacts rapidly with NO. To study the global effects of ship emissions we used a simple upscaling approach which suggested that the parameterization of ship emissions in global chemistry models as a constant source at the sea surface leads to an overestimation of the effects of ship emissions on O 3 of about 50% and on OH of roughly a factor of 2. The differences are mainly caused by a strongly reduced lifetime (compared to background air) of NO x in the early stages of a ship plume.

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“…The MAST experiment studied ship tracks for one month off the coast of California. The results gained from the analysis of 131 ship tracks produced by known ships showed that the average ship track had length 296±233 km and width 9±5 km (Durkee et al, 2000a). Ship tracks are rarely found in cloud at an altitude above 1 km (Coakley et al, 2000).…”

Section: E Campmany Et Al: Detection Of Ship Tracks In Atsr-2 Satelmentioning

confidence: 99%

“…These conditions include a small boundary layer depth, pre-existing cloud formation mechanisms, and CCN concentrations below a threshold value. The MAST study returned average values of wind speed of 7.8 ms −1 , surface pressure of 1018.3 mb and surface temperature of 287.8 K (Durkee et al, 2000a). Albrecht (1989) proposed one further effect ship tracks could have on cloud cover, and hence the climate: a reduction in drizzle.…”

Section: E Campmany Et Al: Detection Of Ship Tracks In Atsr-2 Satelmentioning

confidence: 99%

Automatic detection of ship tracks in ATSR-2 satellite imagery

et al. 2009

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Abstract. Ships modify cloud microphysics by adding cloud condensation nuclei (CCN) to a developing or existing cloud. These create lines of larger reflectance in cloud fields that are observed in satellite imagery. An algorithm has been developed to automate the detection of ship tracks in Along Track Scanning Radiometer 2 (ATSR-2) imagery. The scheme has been integrated into the Global Retrieval of ATSR Cloud Parameters and Evaluation (GRAPE) processing chain. The algorithm firstly identifies intensity ridgelets in clouds which have the potential to be part of a ship track. This identification is done by comparing each pixel with its surrounding ones. If the intensity of three adjacent pixels is greater than the intensity of their neighbours, then it is classified as a ridgelet. These ridgelets are then connected together, according to a set of connectivity rules, to form tracks which are classed as ship tracks if they are long enough. The algorithm has been applied to two years of ATSR-2 data. Ship tracks are most frequently seen off the west coast of California, and the Atlantic coast of both West Africa and SouthWestern Europe. The global distribution of ship tracks shows strong seasonality, little inter-annual variability and a similar spatial pattern to the distribution of ship emissions.

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Composite Ship Track Characteristics

Cited by 84 publications

References 14 publications

Impact of ship emissions on the microphysical, optical and radiative properties of marine stratus: a case study

Impact of ship emissions on the microphysical, optical and radiative properties of marine stratus: a case study

Modeling the chemical effects of ship exhaust in the cloud-free marine boundary layer

Automatic detection of ship tracks in ATSR-2 satellite imagery

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