Automatic detection of ship tracks in ATSR-2 satellite imagery

Campmany, E.; Grainger, Roy G.; Dean, S. M.; Sayer, A. M.

doi:10.5194/acp-9-1899-2009

Cited by 26 publications

(22 citation statements)

References 14 publications

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“…Studies of ship track occurrence on a global scale with satellite observations was, to our knowledge, performed by two studies. Schreier et al [2007] used 1 year data to compile a global statistic of ship tracks identified by visual analysis, whereas Campmany et al [2009] utilized an automatic ship track detection algorithm. Both studies find accumulations of ship tracks over similar regions of the worlds' oceans with the exception that Campmany et al [2009] did not find any tracks off the coast of Africa (an updated version of the algorithm also finds some tracks off the coast of Africa (A. M. Sayer, personal communication, 2011)).…”

Section: Introductionmentioning

confidence: 99%

A search for large-scale effects of ship emissions on clouds and radiation in satellite data

Peters¹,

Quaas²,

Graßl³

2011

J. Geophys. Res.

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[1] Ship tracks are regarded as the most obvious manifestations of the effect of anthropogenic aerosol particles on clouds (indirect effect). However, it is not yet fully quantified whether there are climatically relevant effects on large scales beyond the narrow ship tracks visible in selected satellite images. A combination of satellite and reanalysis data is used here to analyze regions in which major shipping lanes cut through otherwise pristine marine environments in subtropical and tropical oceans. We expect the region downwind of a shipping lane is affected by the aerosol produced by shipping emissions but not the one upwind. Thus, differences in microphysical and macrophysical cloud properties are analyzed statistically. We investigate microphysical and macrophysical cloud properties as well as the aerosol optical depth and its fine-mode fraction for the years 2005-2007 as provided for by retrievals of the two Moderate Resolution Imaging Spectroradiometer instruments. Water-cloud properties include cloud optical depth, cloud droplet effective radius, cloud top temperature, and cloud top pressure. Large-scale meteorological parameters are taken from ERA-Interim reanalysis data and microwave remote sensing (sea surface temperature). We analyze the regions of interest in a Eulerian and Lagrangian sense, i.e., sampling along shipping lanes and sampling along wind trajectories, respectively. No statistically significant impacts of shipping emissions on large-scale cloud fields could be found in any of the selected regions close to major shipping lanes. In conclusion, the net indirect effects of aerosols from ship emissions are not large enough to be distinguishable from the natural dynamics controlling cloud presence and formation.Citation: Peters, K., J. Quaas, and H. Graßl (2011), A search for large-scale effects of ship emissions on clouds and radiation in satellite data,

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Section: Introductionmentioning

confidence: 99%

A search for large-scale effects of ship emissions on clouds and radiation in satellite data

Peters¹,

Quaas²,

Graßl³

2011

J. Geophys. Res.

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“…The retrievals have already been used to study ship tracks (Campmany et al, 2009;Sayer and Grainger, 2010) and study cloud-aerosol interactions (Bulgin et al, 2008). It is noted that, while the authors have applied the algorithm Table 1.…”

Section: A Poulsen Et Al: Cloud Retrieval Algorithmmentioning

confidence: 99%

Cloud retrievals from satellite data using optimal estimation: evaluation and application to ATSR

Poulsen

Siddans

Thomas³

et al. 2012

Atmos. Meas. Tech.

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Abstract. Clouds play an important role in balancing the Earth's radiation budget. Hence, it is vital that cloud climatologies are produced that quantify cloud macro and micro physical parameters and the associated uncertainty. In this paper, we present an algorithm ORAC (Oxford-RAL retrieval of Aerosol and Cloud) which is based on fitting a physically consistent cloud model to satellite observations simultaneously from the visible to the mid-infrared, thereby ensuring that the resulting cloud properties provide both a good representation of the short-wave and long-wave radiative effects of the observed cloud. The advantages of the optimal estimation method are that it enables rigorous error propagation and the inclusion of all measurements and any a priori information and associated errors in a rigorous mathematical framework. The algorithm provides a measure of the consistency between retrieval representation of cloud and satellite radiances. The cloud parameters retrieved are the cloud top pressure, cloud optical depth, cloud effective radius, cloud fraction and cloud phase.The algorithm can be applied to most visible/infrared satellite instruments. In this paper, we demonstrate the applicability to the Along-Track Scanning Radiometers ATSR-2 and AATSR. Examples of applying the algorithm to ATSR-2 flight data are presented and the sensitivity of the retrievals assessed, in particular the algorithm is evaluated for a number of simulated single-layer and multi-layer conditions. The algorithm was found to perform well for single-layer cloud except when the cloud was very thin; i.e., less than 1 optical depths. For the multi-layer cloud, the algorithm was robust except when the upper ice cloud layer is less than five optical depths. In these cases the retrieved cloud top pressure and cloud effective radius become a weighted average of the 2 layers. The sum of optical depth of multi-layer cloud is retrieved well until the cloud becomes thick, greater than 50 optical depths, where the cloud begins to saturate. The cost proved a good indicator of multi-layer scenarios. Both the retrieval cost and the error need to be considered together in order to evaluate the quality of the retrieval. This algorithm in the configuration described here has been applied to both ATSR-2 and AATSR visible and infrared measurements in the context of the GRAPE (Global Retrieval and cloud Product Evaluation) project to produce a 14 yr consistent record for climate research.

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“…Durkee et al, 2000;Ackerman et al, 2000;Campmany et al, 2009;Christensen and Stephens, 2011). Ship tracks provide an ideal experiment for isolating the impact of aerosols, as the polluted clouds are similar in origin and thickness to clean clouds in the surrounding cloud deck, although they may be elevated in height (Christensen and Stephens, 2011).…”

Section: Aerosol Indirect Effectsmentioning

confidence: 99%

Systematic satellite observations of the impact of aerosols from passive volcanic degassing on local cloud properties

et al. 2014

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Abstract. The impact of volcanic emissions, especially from passive degassing and minor explosions, is a source of uncertainty in estimations of aerosol indirect effects. Observations of the impact of volcanic aerosol on clouds contribute to our understanding of both present-day atmospheric properties and of the pre-industrial baseline necessary to assess aerosol radiative forcing. We present systematic measurements over several years at multiple active and inactive volcanic islands in regions of low present-day aerosol burden. The time-averaged indirect aerosol effects within 200 km downwind of island volcanoes are observed using Moderate Resolution Imaging Spectroradiometer (MODIS, 2002–2013) and Advanced Along-Track Scanning Radiometer (AATSR, 2002–2008) data. Retrievals of aerosol and cloud properties at Kīlauea (Hawai'i), Yasur (Vanuatu) and Piton de la Fournaise (la Réunion) are rotated about the volcanic vent to be parallel to wind direction, so that upwind and downwind retrievals can be compared. The emissions from all three volcanoes – including those from passive degassing, Strombolian activity and minor explosions – lead to measurably increased aerosol optical depth downwind of the active vent. Average cloud droplet effective radius is lower downwind of the volcano in all cases, with the peak difference ranging from 2–8 μm at the different volcanoes in different seasons. Estimations of the difference in Top of Atmosphere upward Short Wave flux upwind and downwind of the active volcanoes from NASA's Clouds and the Earth's Radiant Energy System (CERES) suggest a downwind elevation of between 10 and 45 Wm−2 at distances of 150–400 km from the volcano, with much greater local (< 80 km) effects. Comparison of these observations with cloud properties at isolated islands without degassing or erupting volcanoes suggests that these patterns are not purely orographic in origin. Our observations of unpolluted, isolated marine settings may capture processes similar to those in the pre-industrial marine atmosphere.

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Automatic detection of ship tracks in ATSR-2 satellite imagery

Cited by 26 publications

References 14 publications

A search for large-scale effects of ship emissions on clouds and radiation in satellite data

A search for large-scale effects of ship emissions on clouds and radiation in satellite data

Cloud retrievals from satellite data using optimal estimation: evaluation and application to ATSR

Systematic satellite observations of the impact of aerosols from passive volcanic degassing on local cloud properties

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