Publication Abstracts

Chen 2000

Chen, T., 2000: Towards a More Complete Understanding of Cloud Radiative Effects. Ph.D. thesis. Columbia University.

Radiative flux changes induced by the occurrence of different cloud types are investigated using ISCCP cloud data and a refined radiative transfer model from NASA/GISS GCM. Cloud-type variations are shown to be as important as cloud cover in modifying the radiation field of the earth-atmosphere system. Other variables, such as the solar insolation and atmospheric and surface properties, also play significant roles in determining regional cloud radiative effects. To study the sensitivity of radiative fluxes and atmospheric radiative heating rate profiles to variations in cloud vertical structure, three different cloud overlap schemes are applied to the ISCCP vertical distribution of clouds in the same radiative transfer model. The results show that the changes in the TOA and surface radiative fluxes vary among the different schemes, depending on the part of the atmosphere-surface system and spectral band (SW and LW) considered, but that the magnitudes of the changes are generally small. The changes in the radiative heating rate profile are quantitatively small as well. However, the magnitude of these changes is similar to the magnitude of the total overall cloud effect, making the layer overlap critical to accurate determinations of the shape of the radiative heating rate profiles. The scheme without a total optical thickness constraint produces opposite signed changes in fluxes (except for the surface LW flux) and the profile of atmospheric radiative heating rate compared with the schemes with the constraint, demonstrating the importance of conserving the total cloud optical thickness when applying any overlap assumption to satellite observations. To identify the sources of disagreement in the ERBE and ISCCP derived OLR, broadband based ERBE and narrowband based ISCCP approaches are applied to the ScaRaB simultaneous narrowband and broadband measurements. Uncertainties in both ERBE and ISCCP approaches contribute to the disagreement. Compared with the radiative transfer model, the LW ERBE ADMs are too weakly limb-darkened for the optically thin clouds, but too strongly limb-darkened for the optically thick clouds, indicating that more accurate instantaneous OLR estimations from ERBE approach would require additional cloud classes based on optical properties.

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BibTeX Citation

  author={Chen, T.},
  title={Towards a More Complete Understanding of Cloud Radiative Effects},
  school={Columbia University},
  address={New York, N.Y.},

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RIS Citation

ID  - ch09500o
AU  - Chen, T.
PY  - 2000
BT  - Towards a More Complete Understanding of Cloud Radiative Effects
PB  - Columbia University
CY  - New York, N.Y.
ER  -

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