The Role of Background Cloud Microphysics in the Radiative Formation of Ship Tracks
نویسندگان
چکیده
The authors investigate the extent to which the contrast brightness of ship tracks, that is, the relative change in observed solar reflectance, in visible and near-infrared imagery can be explained by the microphysics of the background cloud in which they form. The sensitivity of visible and near-infrared wavelengths for detecting reflectance changes in ship tracks is discussed, including the use of a modified cloud susceptibility parameter, termed the ‘‘contrast susceptibility,’’ for assessing the sensitivity of background cloud microphysics on potential track development. It is shown that the relative change in cloud reflectance for ship tracks is expected to be larger in the near-infrared than in the visible and that 3.7-mm channels, widely known to be useful for detecting tracks, have the greatest sensitivity. The usefulness of contrast susceptibility as a predictor of ship track contrast is tested with airborne and satellite remote sensing retrievals of background cloud parameters and track contrast. Retrievals are made with the high spatial resolution Moderate Resolution Imaging Spectroradiometer Airborne Simulator flown on the National Aeronautics and Space Administration’s high-altitude ER-2 aircraft, and with the larger-scale perspective of the advanced very high resolution radiometer. Observed modifications in cloud droplet effective radius, optical thickness, liquid water path, contrast susceptibility, and reflectance contrast are presented for several ship tracks formed in background clouds with both small and large droplet sizes. The remote sensing results are augmented with in situ measurements of cloud microphysics that provide data at the smaller spatial scales.
منابع مشابه
A Simple, Yet Realistic Model for the Formation of Arctic Stratus Clouds–A Case Study
We have developed a one-dimensional radiative-convective model with detailed cloud microphysics, and used it to study the formation of Arctic Stratus clouds (ASC). The model contains detailed radiative and microphysical modules, and it provides a self-consistent treatment of the interaction between radiative and cloud microphysical processes important for cloud formation. The radiative transfer...
متن کاملImpact of ship emissions on the microphysical, optical and radiative properties of marine stratus: a case study
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...
متن کاملA global radiative-convective feedback
We have investigated the sensitivity of the intensity of convective activity and atmospheric radiative cooling to radiatively thick upper-tropospheric clouds using a new version of the Colorado State University General Circulation Model. The model includes a bulk cloud microphysics scheme to predict the formation of cloud water, cloud ice, rain, and snow. The cloud optical properties are intera...
متن کاملHigh-resolution (375 m) cloud microstructure as seen from the NPP/VIIRS satellite imager
VIIRS (Visible Infrared Imaging Radiometer Suite), onboard the Suomi NPP (National Polar-orbiting Partnership) satellite, has an improved resolution of 750 m with respect to the 1000 m of the Moderate Resolution Imaging Spectroradiometer for the channels that allow retrieving cloud microphysical parameters such as cloud drop effective radius (re). VIIRS also has an imager with five channels of ...
متن کاملReal-case simulations of aerosol–cloud interactions in ship tracks over the Bay of Biscay
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 para...
متن کامل