The cloud classification model SCANDIA (SMHI Cloud ANalysis model using DIgital AVHRR data) is described in this report. SCANDIA is based on multispectral processing of NOAA AVHRR imagery where cloud and surface analyses are produced in real-time for use in operational weather forecasting. Also other applications are described, e.g. compilation of cloud climatologies, estimation of snow area coverage and validation of cloud forecasts from numerical weather prediction models.

Two different versions of the SCANDIA model are discussed. The first version was introduced in 1988 and the model structure is explained in detail. Model strengths and weaknesses are described by using comparisons with observed cloudiness from ordinary surface weather observations (SYNOP). Also the feedback response from operational weather forecasters is discussed. The second version was introduced in 1994, now operating on a larger area covering the major parts of northem Europe. Necessary modifications for operating on larger scales are described and new features for the identification and highlighting of situations with serious limitations of classification results are demonstrated.