［ 2017年03月02日 ］
RIKEN International Symposium on Data Assimilation 2017
"Using visible and near-infrared satellite observations for convective-scale data assimilation"
High-resolution observations from instruments on geostationary satellites provide a wealth of information about convective activity and are therefore seen as a important type of observation for convective scale data assimilation (DA). In particular the visible and near-infrared channels provide information on the cloud distribution, cloud microphysical properties and cloud structure with high temporal and spatial resolution. However, in operational DA systems currently only clear sky thermal infrared and microwave radiance observations are used, which mainly provide temperature and humidity information. Sufficiently fast and accurate forward operators for visible and near-infrared radiances are not yet available, because multiple scattering makes radiative transfer at solar wavelengths complicated and computationally expensive. Only recently a we developed a loop-up table based 1D radiative transfer method that is orders of magnitude faster than conventional radiative transfer solvers for the visible spectrum and similarly accurate. A preliminary version of a forward operator based on this method, which simulates synthetic MSG-SEVIRI images from COSMO-DE model output, has been completed and implemented in the pre-operational km-scale Ensemble Data Assimilation (KENDA) system of DWD. To improve the consistency and accuracy of the operator we included computationally cheap methods to account for the overlap of subgrid clouds and the most important 3D radiative transfer effects. We present this novel operator and first results from assimilation experiments.
|名前:Leonhard Scheck||所属:Ludwig-Maximilians-University of Munich|