A study of atmospheric turbidity for Hong Kong

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