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ABSTRACTS The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission represents the National Aeronautics and Space Administration's (NASA) next investment in satellite ocean color and the study of Earth's ocean-atmosphere system, [...]

Retrievals of atmospheric carbon dioxide (C[O.sub.2]) from space-borne measurements of backscattered near-infrared sunlight are hampered by aerosol and cirrus cloud scattering effects. We propose a retrieval approach that allows for the retrieval of a few effective aerosol parameters simultaneously with the C[O.sub.2] total column by parameterizing particle amount, height distribution, and microphysical properties. Two implementations of the proposed method covering different spectral bands are tested for an ensemble of simulated nadir observations for aerosol (and cirrus) loaded scenes over low- and mid-latitudinal land surfaces. The residual aerosol-induced C[O.sub.2] errors are mostly below 1% up to aerosol optical thickness 0.5. The proposed methods also perform convincing for scenes where cirrus clouds of optical thickness 0.1 overlay the aerosol. OCIS codes: 010.0280, 010.1280, 010.1310, 120.6200, 290.1090.

We investigate the capabilities of different instrument concepts for the retrieval of aerosol properties over land. It was found that, if the surface reflection properties are unknown, only multiple-viewing-angle measurements of both intensity and polarization are able to provide the relevant aerosol parameters with sufficient accuracy for climate research. Furthermore, retrieval errors are only little affected when the number of viewing angles is increased at the cost of the number of spectral sampling points and vice versa. This indicates that there is a certain amount of freedom for the instrument design of dedicated aerosol instruments. The final choice on the trade-off between the spectral sampling and the number of viewing angles should be made taking other factors into account, such as instrument complexity and the ability to obtain global coverage. OCIS codes: 010.1100, 280.1100, 290.1090, 290.1350.

We present what we believe to be a novel approach to simulating the spectral fine structure ( OCIS codes: 010.0010, 040.1240, 070.4790, 290.5860, 300.6330.

Accurate radiative transfer calculations in cloudy atmospheres are generally time consuming, limiting their practical use in satellite remote sensing applications. We present a model to efficiently calculate the radiative transfer of polarized light in atmospheres that contain homogeneous cloud layers. This model combines the Gauss--Seidel method, which is efficient for inhomogeneous cloudless atmospheres, with the doubling method, which is efficient for homogeneous cloud layers. Additionally to reduce the computational effort for radiative transfer calculations in absorption bands, the cloud reflection and transmission matrices are interpolated over the absorption and scattering optical thicknesses within the cloud layer. We demonstrate that the proposed radiative transfer model in combination with this interpolation technique is efficient for the simulation of satellite measurements for inhomogeneous atmospheres containing one homogeneous cloud layer. For example, the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) measurements in the oxygen A band (758-773 nm) and the Hartley-Huggins ozone band (295-335 nm) with a spectral resolution of 0.4 nm can be simulated for these atmospheres within 1 min on a 2.8 GHz PC with an accuracy better than 0.1%. OCIS codes: 290.1090, 280.1310, 010.1310, 290.1350.