Effects of optical depth variability on contrail radiative forcing

Kärcher, B.; Burkhardt, Ulrike

doi:10.1002/qj.2053

Cited by 6 publications

(10 citation statements)

References 22 publications

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“…Vázquez-Navarro et al (2015) found larger mean values because their method mainly detects geometrically and optically thick contrails. The shape of the SW and LW RF pdfs is similar to theory predictions (Kärcher and Burkhardt, 2013), but negative RF values were not expected in that study.…”

Section: Contrail Propertiessupporting

confidence: 85%

“…The pdf of log τ has a negative skewness: a few contrails thicken, while most have small τ , and some are subvisible. The same type of asymmetry in the pdf of log τ has been simulated by Kärcher and Burkhardt (2013) for contrails and measured by Immler et al (2008) for contrail cirrus. The global mean optical depth τ is 0.29, which is close to values observed for young contrails .…”

Section: Contrail Propertiesmentioning

confidence: 56%

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Dehydration effects from contrails in a coupled contrail–climate model

et al. 2015

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Abstract. The uptake of water by contrails in icesupersaturated air and the release of water after ice particle advection and sedimentation dehydrates the atmosphere at flight levels and redistributes humidity mainly to lower levels. The dehydration is investigated by coupling a plumescale contrail model with a global aerosol-climate model. The contrail model simulates all the individual contrails forming from global air traffic for meteorological conditions as defined by the climate model. The computed contrail cirrus properties compare reasonably with theoretical concepts and observations. The mass of water in aged contrails may exceed 10 6 times the mass of water emitted from aircraft. Many of the ice particles sediment and release water in the troposphere, on average 700 m below the mean flight levels. Simulations with and without coupling are compared. The drying at contrail levels causes thinner and longer-lived contrails with about 15 % reduced contrail radiative forcing (RF). The reduced RF from contrails is on the order of 0.06 W m −2 , slightly larger than estimated earlier because of higher soot emissions. For normal traffic, the RF from dehydration is small compared to interannual variability. A case with emissions increased by 100 times is used to overcome statistical uncertainty. The contrails impact the entire hydrological cycle in the atmosphere by reducing the total water column and the cover by high-and low-level clouds. For normal traffic, the dehydration changes contrail RF by positive shortwave and negative longwave contributions on the order of 0.04 W m −2 , with a small negative net RF. The total net RF from contrails and dehydration remains within the range of previous estimates.

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Section: Contrail Propertiessupporting

confidence: 85%

Section: Contrail Propertiesmentioning

confidence: 56%

Dehydration effects from contrails in a coupled contrail–climate model

et al. 2015

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“…Figure 6 also depicts the resulting model PDF of contrail OD and its cumulant, along with an observed cumulative PDF 56 . The model PDF derives from an analysis of satellite observations 66 and contains many optically thin and even invisible portions within contrails. This indicates that contrails that are non-detectable by passive remote sensing and invisible by ground-based observers may exert a non-negligible RF despite their low OD, since they are likely associated with large coverage 67 .…”

Section: Radiative and Climate Impactmentioning

confidence: 99%

Formation and radiative forcing of contrail cirrus

2018

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Aircraft-produced contrail cirrus clouds contribute to anthropogenic climate change. Observational data sets and modelling approaches have become available that clarify formation pathways close to the source aircraft and lead to estimates of the global distribution of their microphysical and optical properties. While contrail cirrus enhance the impact of natural clouds on climate, uncertainties remain regarding their properties and lifecycle. Progress in representing aircraft emissions, contrail cirrus and natural cirrus in global climate models together with tighter constraints on the sensitivity of the climate system will help judge efficiencies of and trade-offs between mitigation options.

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“…The cumulative distribution function of optical depth  (near 550 nm) has a negative skewness, see Fig. 5: A few contrails get thick while most have small ; some are subvisible, and only the thicker ones are observable (Immler et al 2008;Kärcher and Burkhardt 2013).…”

Section: Optical Propertiesmentioning

confidence: 99%

On the Life Cycle of Individual Contrails and Contrail Cirrus

Schumann

Heymsfield

2017

Meteorological Monographs

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The life cycle of individual (initially line shaped) contrails behind aircraft and of contrail cirrus (aged contrails mixed with other ice clouds) is described. The full contrail life cycle is covered, from ice formation for given water, heat, and particulate emissions; to changes in the jet, wake, and dispersion phases; through final sublimation or sedimentation. Contrail properties are deduced from various in situ, remote sensing, and model studies. Aerodynamically induced contrails and distrails are explained briefly. Contrails form both in clear air and inside cirrus. Young contrails consume most of the ambient ice supersaturation. Optical properties of contrails are age and humidity dependent. Contrail occurrence and radiative forcing depends on the ambient Earth–atmosphere conditions. Contrail cirrus seems to be optically thicker than assessed previously and may not only increase cirrus coverage but also thicken existing cirrus. Some observational constraints for contrail cirrus occurrence and radiative forcing are derived. Key parameters controlling contrail properties—besides aircraft and fuel properties, ambient pressure, temperature, and humidity—are the number of ice particles per flight distance surviving the wake vortex phase, the contrail depth, and particle sedimentation, wind shear, turbulence, and vertical motions controlling contrail dispersion. The climate impact of contrails depends among other things on the ratio of shortwave to longwave radiative forcing (RF) and on the efficacy with which contrail RF contributes to surface warming. Several open issues are identified, including renucleation from residuals of sublimated contrail ice particles.

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Effects of optical depth variability on contrail radiative forcing

Cited by 6 publications

References 22 publications

Dehydration effects from contrails in a coupled contrail–climate model

Dehydration effects from contrails in a coupled contrail–climate model

Formation and radiative forcing of contrail cirrus

On the Life Cycle of Individual Contrails and Contrail Cirrus

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