Publication: A 3D cloud-construction algorithm for the EarthCARE satellite mission
All || By Area || By Year| Title | A 3D cloud-construction algorithm for the EarthCARE satellite mission | Authors/Editors* | H. W. Barker, M. P. Jerg, T. Wehr, S. Kato, D. P. Donovan and R. J. Hogan |
|---|---|
| Where published* | Quarterly Journal of the Royal Meteorological Society |
| How published* | Journal |
| Year* | 2011 |
| Volume | |
| Number | DOI:10.1002/qj.824 |
| Pages | 17 |
| Publisher | Royal Meteorological Society |
| Keywords | cloud; radiative transfer; satellite; EarthCARE |
| Link | |
| Abstract |
This article presents and assesses an algorithm that constructs 3D distributions of cloud from passive satellite imagery and collocated 2D nadir profiles of cloud properties inferred synergistically from lidar, cloud radar and imager data. It effectively widens the activeâpassive retrieved cross-section (RXS) of cloud properties, thereby enabling computation of radiative fluxes and radiances that can be compared with measured values in an attempt to perform radiative closure experiments that aim to assess the RXS. For this introductory study, A-train data were used to verify the scene-construction algorithm and only 1D radiative transfer calculations were performed. The construction algorithm fills off-RXS recipient pixels by computing sums of squared differences (a cost function F) between their spectral radiances and those of potential donor pixels/columns on the RXS. Of the RXS pixels with F lower than a certain value, the one with the smallest Euclidean distance to the recipient pixel is designated as the donor, and its retrieved cloud properties and other attributes such as 1D radiative heating rates are consigned to the recipient. It is shown that both the RXS itself and Moderate Resolution Imaging Spectroradiometer (MODIS) imagery can be reconstructed extremely well using just visible and thermal infrared channels. Suitable donors usually lie within 10 km of the recipient. RXSs and their associated radiative heating profiles are reconstructed best for extensive planar clouds and less reliably for broken convective clouds. Domain-average1Dbroadbandradiative fluxes at the top of the atmosphere(TOA) for (21 km)2 domains constructed from MODIS, CloudSat andCloudâAerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data agree well with coincidental values derived from Clouds and the Earthâs Radiant Energy System (CERES) radiances: differences betweenmodelled and measured reflected shortwave fluxes are within±10Wmâ2 forâ¼35% of the several hundred domains constructed for eight orbits. Correspondingly, for outgoing longwave radiationâ¼65% are within ±10Wmâ2. |
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