ISCCP_DX cloud products in support of BALTEX

Abstract

Within the framework of BALTEX (Baltic Sea Experiment), the European GEWEX (Global Energy and Water Cycle Experiment) regional study, a regional atmospheric model REMO (horizontal resolution 18km) is used at GKSS to study the exchange of energy and water between surface and atmosphere over the Baltic sea catchment area. For such numerical model calculations of water and energy balances to be reliable, ideally the model should be validated over the whole computational domain with high spatiotemporal resolution, for which satellite data are particularly well suited. The International Satellite Cloud Climatology Project (ISCCP) has been for more than a decade collecting data of the operational satellites. While those data in general are used to improve understanding of the cloud and radiation problems with a typical resolution of 280×280 km 2, there have to be new studies initiated focusing on how to use these data for the retrieval of regional radiation budget products related to the spatiotemporal scales of the regional models. We compare results of our REMO predictions against products of the ISCCP_DX data. These products are derived for individual instantaneous satellite field of views of about 4km 2 sampled horizontally every 30km with a 3 hourly time resolution. To compare ISCCP_DX products against model predictions for a 18×18km 2 grid cell we take into account the ISCCP sampling within such a grid cell to retain temporal and spatial information in model output and observations.