Cloud height measurement by a network of all-sky imagers

Abstract. Cloud base height (CBH) is an important parameter for many applications such as aviation, climatology or solar irradiance nowcasting (forecasting the next seconds to hours ahead). The latter application of increasing importance operation distribution grids and photovoltaic power plants, energy storage systems flexible consumers. To nowcast irradiance, based on all-sky imagers (ASIs), cameras monitoring entire sky dome above their point installation, have been demonstrated. Accurate knowledge CBH required spatial around ASI's location at a resolution down 5 m. measure CBH, two ASIs located distance usually less than 6 km can be combined into ASI pair. However, accuracy limited. We present validate method using network enhance accuracy. best our knowledge, this first with which demonstrated experimentally. In study, deviations 42 pairs are studied in comparison ceilometer characterized by camera distance. formed from seven feature distances 0.8…5.7 km. Each 21 tuples yields independent used main auxiliary camera, respectively, swapped. Deviations found compiled conditional probabilities that tell how probable it receive certain reading pair given true takes some specific value. Based statistical inference, likeliest actual estimated readings all pairs. validation results, small (especially if <1.2 km) accurate low clouds (CBH<4 km). contrast, more 3 provide smaller greater CBH. No provides most measurements under conditions. presented different proves that, cloud conditions, single