Determination of the visibility using a digital panorama camera

We describe a method to determine the daytime visibility at a station that is located at the University of Karlsruhe, Germany. A comparison of visibilities determined by applying our new method and visibilities observed with standard methods at a nearby station of the German Weather Service (DWD) demonstrate the successful operation of our method. The highest differences occur for very low and very high visibilities. For visibilities > 10 km, the correlation between visibilities of both methods is 0.73. Additionally, at low sun zenith angles of <30 degrees, an overestimation by the visibility determined with digital photographs (VISIDIP) method of up to 20% has been observed. Partially, the bias could be explained by the different measurement heights and different local conditions which have an effect especially under certain meteorological conditions as fog or precipitation events. In contrast to human observations, the new method presented in this feasibility study is completely automatic and objective. (C) 2007 Elsevier Ltd. All rights reserved.