Analyses of haze and mist situations over Swiss lowlands during summer smog-periods with NOAA-AVHRR data

Within the Swiss interdisciplinary summer-smog research programme POLLUMET (POLLUtion and METeorology), systematical analyses of haze and mist concentrations over the Swiss lowlands with digital weather-satellite data (NOAA-AVHRR) were made. The aim of this study was to learn about the temporal and spatial behaviour of haze and mist which is very important for air pollution situations. A model was created which is based on the calculation of the sky light reaching the satellite sensor in the visible and near-infrared channels. The sky light is caused by the particles in the lower region of the troposphere (haze and mist causing particles) and, therefore, the sky light can be considered proportional to the loading of haze and mist. Taking the sky light as an indicator of haze and mist, the main advantages are that no additional information concerning the atmosphere is needed and the parameter "sky light" is itself one part of the incoming radiation at the satellite sensor. With the model developed, this amount of the signal received at the satellite sensor can be calculated. With this new tool, time series of haze and mist concentrations during summer smog-periods over the Swiss lowlands could be calculated and analysed. The main interest focused on the behaviour of haze and mist quantities in different areal scales and over different objects on the earth's surface. The analyses showed interesting and even surprising results.