Some Models for Visibility for German Stations.

Abstract : A goal of the Air Weather Service is to be able to expeditiously give the probability that a weather element will have a value above a specified threshold for any location and any time. In previous reports, the present investigators have shown how probability models can be constructed for such weather elements as visibility, ceiling, sky cover, precipitation and windspeed for stations where records exist, so that the required probabilities can be easily calculated. More recently studies have been made to develop models for visibility where data does not exist. The pilot study was made using data from Germany. Models for visibility were developed for thirty German stations for different months and times of day using the Weibull distribution. Regression runs were made to obtain expressions for parameter estimates as functions of variables such as elevation, relative elevation, proximity to water, direction of terrain at the station, etc. These expressions are then usable to obtain Weibull model parameter estimates for arbitrary locations. The present report gives the Weibull parameter estimates for the thirty German stations for each month of the year and eight times of day. Measures of model accuracies for the different stations are also given. The data used to develop the models was extracted from the 'Revised Uniform Summary of Weather Observations' (RUSSWO's) prepared by the Data Processing Division of the Air Weather Service. (Author)