The variability of cloud cover and cloud forcing inferred from NOAA AVHRR data for the North Sea

• Published in: Advances in space research Vol. 16; no. 10; pp. 29 - 32
• Main Author: Berger, F.H.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1995
• ISSN: 0273-1177; 1879-1948
• DOI: 10.1016/0273-1177(95)00376-P

From August 1990 until September 1994, NOAA AVHRR HRPT data were analysed to determine the variability of cloud cover and of cloud forcing at top of atmosphere (TOA) for the North Sea (1300×1300 km 2). The first step was a detailed cloud classification based on the maximum likelihood method. That classification scheme allows a discrimination of 24 cloud classes, especially high clouds with different optical properties. The validation of these results is based on synoptical observations. Therefore, the annual variability of cloud cover can be shown for individual synoptical ground stations and for larger areas inferred from satellite data. Due to an overlapping period with ISCCP C2 data, a comparison with the high-resolution results was carried out. That led to a 10 year cloud cover climatology (1983–1993) for the North Sea, where 24 grid areas (each 2.5°×2.5°) could be investigated. A further step is the computation of cloud-climate efficiency and cloud forcing at top of atmosphere, where cloud forcing is the area mean of cloud-climate efficiencies. The cloud-climate efficiency is the cloud forcing of an individual classified cloud. For the analysed period, the variability of cloud forcing depends strongly on the cloud cover variability. Thus, the drought 1992 in Schleswig-Holstein and in northern Germany can be detected and the influence of high clouds, their amplifying heating effect, can be shown.