A study of atmospheric turbidity for Hong Kong

Clear skies are important in predicting the peak solar irradiance and daylight illuminance levels for active solar energy utilisation and passive energy-efficient building designs. The clearness of a sky is affected by the clarity of the atmosphere which is usually expressed in terms of a turbidity index. This study considers two common turbidity parameters including the Linke turbidity factor (T-L) and Angstrom turbidity coefficient (beta). The annual and monthly average values, frequency of occurrence and cumulative frequency distribution of individual turbidity indices based on different approaches have been established to describe the clear sky atmospheric conditions in Hong Kong. The general features and characteristics of the findings are discussed. (C) 2001 Elsevier Science Ltd. All fights reserved.