The EU‐CLOUDMAP project: Cirrus and contrail cloud‐top maps from satellites for weather forecasting climate change analysis

Abstract

The EU‐CLOUDMAP project took place between 1997–2000 as a collaboration between five university and government research groups in the UK, Germany, the Netherlands and Switzerland. The original scientific motivation of the EU‐CLOUDMAP Project was to improve the measurement and characterization of cirrus and contrail cloud properties. IPCC (Penner et al.1999) demonstrated that contrail clouds could play a small but significant role in changing the radiative balance of the atmosphere based on work from one of the CLOUDMAP partners (DLR) using AVHRR data over Europe. However, the scope was broadened to include properties of clouds at all altitudes as (Cess et al.1993) had shown that depending on how cloud processes are parameterised can lead to an order of magnitude difference in predictions of surface temperature due to changes in CO2 radiative forcing. This error is by far the largest uncertainty in making accurate forecasts of global warming. The primary technological motivation of the Project was to develop new techniques for deriving cloud‐top properties (cloud‐top height, amount, microphysics and winds) from a new series of meteorological sensors based on the use of either cloud‐top stereo (ATSR‐2 and MISR) or Oxygen A‐band (MOS) and their application to the generation of new cloud climatology products. A secondary goal was to develop an automated technique, based on fuzzy logic, to detect contrails in non‐thermal imagery where contrails can only be detected through their unique spatial characteristics. Validation of cloud products was perceived as a crucial central issue to any adoption of these products by the Numerical Weather Prediction (NWP) and climate forecasting communities. This presents unique challenges as validation must be conducted simultaneously with satellite data acquisition. Ground‐based remote sensing techniques exploiting continuously operating radars and lidars were used and a new technique based on visible stereo digital cameras for retrieving cloud‐base properties was pioneered. A technology spin‐off from the CLOUDMAP work at UCL was the development of an uncooled thermal IR fish‐eye lens camera for continuously monitoring cloud cover from the ground to replace existing manual observations of cloud cover (Chapman et al. 2007). Eight papers in this issue show some of the highlights of the project including fundamental aspects of the algorithms for retrieval of cloud‐top height using stereo photogrammetry from ATSR‐2 (Muller et al. 2007, Denis et al. 2007) and MOMS (Drescher 2007) and Oxygen A‐band from MOS (Preusker et al. 2007). Seiz et al. (2007) describe the development of a novel technique for the automated retrieval of cloud‐base height from stereo visible digital cameras. Naud et al. (2007) describe the validation of cloud‐top heights from ATSR‐2 and MOS using ground‐based radar and lidar. Hetzheim (2007) shows how fuzzy logic systems can be employed for contrail detection when thermal imagery is not available using MOS and ATSR‐2 to demonstrate his techniques. Finally, Meyer et al. (2007) show results from applying the thermal IR contrail detection technique to AVHRR over Asia.