Limits to the Aerosol Indirect Radiative Effect Derived from Observations of Ship Tracks

Coakley, James A.; Walsh, Christopher D.

doi:10.1175/1520-0469(2002)059<0668:lttair>2.0.co;2

Cited by 129 publications

(136 citation statements)

References 29 publications

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“…It turned out that even for rather high aerosol optical depths the change of the AMFs are <50% and could not explain the observed HCHO increase assuming typical background concentrations of HCHO . It is interesting to note that large enhancements of the AMF occur only for scattering aerosols (single scattering albedo close to unity) which is probably a too high value for ship emissions (Coakley and Walsh, 2001). Also, if aerosols from ship emissions were purely scattering aerosols with high optical depth, the corresponding strong increase of the top of the atmosphere radiance should be clearly visible, e.g.…”

Section: Comparison With Model Resultssupporting

confidence: 61%

Satellite measurements of formaldehyde linked to shipping emissions

et al. 2009

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Abstract. International shipping is recognized as a pollution source of growing importance, in particular in the remote marine boundary layer. Nitrogen dioxide originating from ship emissions has previously been detected in satellite measurements. This study presents the first satellite measurements of formaldehyde (HCHO) linked to shipping emissions as derived from observations made by the Global Ozone Monitoring Experiment (GOME) instrument.We analyzed enhanced HCHO tropospheric columns from shipping emissions over the Indian Ocean between Sri Lanka and Sumatra. This region offers good conditions in term of plume detection with the GOME instrument as all ship tracks follow a single narrow track in the same east-west direction as used for the GOME pixel scanning. The HCHO signal alone is weak but could be clearly seen in the highpass filtered data. The line of enhanced HCHO in the Indian Ocean as seen in the 7-year composite of cloud free GOME observations clearly coincides with the distinct ship track corridor from Sri Lanka to Indonesia. The observed mean HCHO column enhancement over this shipping route is about 2.0×10 15 molec/cm 2 .Compared to the simultaneously observed NO 2 values over the shipping route, those of HCHO are substantially higher; also the HCHO peaks are found at larger distance from the ship routes. These findings indicate that direct emissions of HCHO or degradation of emitted NMHC cannot explain the observed enhanced HCHO values. One possible reason might be increased CH 4 degradation due to enhanced Correspondence to: T. Marbach (thierry.marbach@mpic.de) OH concentrations related to the ship emissions, but this source is probably too weak to fully explain the observed values.The observed HCHO pattern also agrees qualitatively well with results from the coupled earth system model ECHAM5/MESSy applied to atmospheric chemistry (EMAC). However, the modelled HCHO values over the ship corridor are two times lower than in the GOME high-pass filtered data. This might indicate uncertainties in the satellite data and used emission inventories and/or that the in-plume chemistry taking place in the narrow path of the shipping lanes are not well represented at the rather coarse model resolution.

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Section: Comparison With Model Resultssupporting

confidence: 61%

Satellite measurements of formaldehyde linked to shipping emissions

et al. 2009

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“…From model simulations of stratocumulus, Ackerman et al (2004) found that when the relative humidity (RH) above cloud top is high, cloud LWP increases with N c consistent with theoretical arguments (Albrecht, 1989;Pincus and Baker, 1994), but that when the RH is low, the LWP decreases when N c increases, as supported by some observations (Coakley and Walsh, 2002). The difference was attributed to the consequence of dry air into a cloud layer.…”

Section: Discussionmentioning

confidence: 99%

Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

et al. 2016

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Abstract. The properties of low-level liquid clouds in the Arctic can be altered by long-range pollution transport to the region. Satellite, tracer transport model, and meteorological data sets are used here to determine a net aerosol-cloud interaction (ACI net ) parameter that expresses the ratio of relative changes in cloud microphysical properties to relative variations in pollution concentrations while accounting for dry or wet scavenging of aerosols en route to the Arctic. For a period between 2008 and 2010, ACI net is calculated as a function of the cloud liquid water path, temperature, altitude, specific humidity, and lower tropospheric stability. For all data, ACI net averages 0.12±0.02 for cloud-droplet effective radius and 0.16±0.02 for cloud optical depth. It increases with specific humidity and lower tropospheric stability and is highest when pollution concentrations are low. Carefully controlling for meteorological conditions we find that the liquid water path of arctic clouds does not respond strongly to aerosols within pollution plumes. Or, not stratifying the data according to meteorological state can lead to artificially exaggerated calculations of the magnitude of the impacts of pollution on arctic clouds.

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“…Moreover, sulphate aerosol has an indirect climate effect influencing cloud structure and properties (e.g., Conover, 1966;Coakley and Walsh, 2002) The present paper presents the first experimental identification and quantification of SO 2− 4 from HFO combustion aerosol based on chemical analyses of PM 10 samples collected at the island of Lampedusa in the central Mediterranean Sea.…”

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confidence: 99%

Evidence for heavy fuel oil combustion aerosols from chemical analyses at the island of Lampedusa: a possible large role of ships emissions in the Mediterranean

et al. 2012

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Abstract. Measurements of aerosol chemical composition made on the island of Lampedusa, south of the Sicily channel, during years [2004][2005][2006][2007][2008], are used to identify the influence of heavy fuel oil (HFO) combustion emissions on aerosol particles in the Central Mediterranean. Aerosol samples influenced by HFO are characterized by elevated Ni and V soluble fraction (about 80 % for aerosol from HFO combustion, versus about 40 % for crustal particles), high V and Ni to Si ratios, and values of V sol > 6 ng m −3 . Evidence of HFO combustion influence is found in 17 % of the daily samples. Back trajectories analysis on the selected events show that air masses prevalently come from the Sicily channel region, where an intense ship traffic occurs. This behavior suggests that single fixed sources like refineries are not the main responsible for the elevated V and Ni events, which are probably mainly due to ships emissions.V sol , Ni sol , and non-sea salt SO 2− 4 (nssSO 2− 4 ) show a marked seasonal behaviour, with an evident summer maximum. Such a pattern can be explained by several processes: (i) increased photochemical activity in summer, leading to a faster production of secondary aerosols, mainly nssSO 2− 4 , from the oxidation of SO 2 (ii) stronger marine boundary layer (MBL) stability in summer, leading to higher concentration of emitted compounds in the lowest atmospheric layers. A very intense event in spring 2008 was studied in detail, also using size segregated chemical measurements. These data show that elements arising from heavy oil combustion (V, Ni, Al, Fe) are distributed in the sub-micrometric fraction of the aerosol, and the metals are present as free metals, carbonates, oxides hydrates or labile complex with organic ligands, so that they are dissolved in mild condition (HNO 3 , pH1.5).Data suggest a characteristic nssSO 2− 4 /V ratio in the range 200-400 for HFO combustion aerosols in summer at Lampedusa. By using the value of 200 a lower limit for the HFO contribution to total sulphates is estimated. HFO combustion emissions account, as a summer average, at least for 1.2 µg m −3 , representing about 30 % of the total nssSO 2− 4 , 3.9 % of PM 10 , 8 % of PM 2.5 , and 11 % of PM1. Within the used dataset, sulphate from HFO combustion emissions reached the peak value of 6.1 µg m −3 on 26 June 2008, when it contributed by 47 % to nssSO 2− 4 , and by 15 % to PM 10 .

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Limits to the Aerosol Indirect Radiative Effect Derived from Observations of Ship Tracks

Cited by 129 publications

References 29 publications

Satellite measurements of formaldehyde linked to shipping emissions

Satellite measurements of formaldehyde linked to shipping emissions

Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

Evidence for heavy fuel oil combustion aerosols from chemical analyses at the island of Lampedusa: a possible large role of ships emissions in the Mediterranean

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