Abstract

The importance of clouds to the radiation balance of the terrestrial climate is well known. Accordingly, state-of-the-art climate models include sophisticated parameterisations of the cloud variables. The aim of the GRAPE project is to produce a global cloud and aerosol dataset using a state-of-the-art physical retrieval of the entire duration of the Along Track Scanning Radiometer 2 (ATSR-2) mission (aboard ERS-2). This dataset will be compared and contrasted with existing climatologies (based on different instruments and very different retrieval algorithms). GRAPE will deliver the following products: Cloud Optical Depth, Aerosol Optical Depth (cloud free), Cloud Phase, Cloud Particle Size, Cloud Top Pressure, Cloud Fraction and Cloud Ice/Water Path along with associated error measurements. The cloud parameters produced will allow a direct comparison with model simulations from the ECMWF and the Met Office Unified Model. In conjunction with water vapour estimates from the MLS instrument aboard UARS, observational estimates of the total water vapour budget will be possible.