Analysis of atmospheric turbidity levels at Taichung Harbor near the Taiwan Strait

In this study, two universal turbidity parameters, the Angstrom turbidity coefficient and Linke turbidity factor, are applied to study the atmospheric turbidity characteristics of Taichung Harbor. Meteorological parameter values were measured during 2004 and 2005 at the Wuchi weather station of the Taiwan Central Weather Bureau, near the Taiwan Strait. Results based on the Angstrom turbidity models (βLou, βPin, and βVis) indicated that annual mean values of the Angstrom turbidity coefficients were 0.174, 0.21 and 0.201, respectively. Four sets of Linke turbidity factors (TLin, TLou, TPin and TVis) were calculated using the original Linke method and the Dogniaux method, incorporating the computed Angstrom turbidity coefficients (βLou, βPin and βVis); the resultant values were 4.30, 6.40, 7.10 and 6.95, respectively. The monthly average values, frequency of occurrence, and cumulative frequency distributions were calculated using different models to describe the clear-sky atmospheric conditions at Taichung Harbor. The frequency results show that for over 50% of the dataset, three sets of Angstrom turbidity coefficients fell between 0.15 and 0.18, and four sets of Linke turbidity factors (TLin, TLou, TPin and TVis) fell between 4.0 and 6.5. Thus, for 50% of cloudless days, the sky can be between turbid and clear over Taichung Harbor. Furthermore, the results reveal that for 30% of the dataset, three Angstrom sets of turbidity coefficients (βLou, βPin, and βVis) exceed 0.2 and four sets of Linke turbidity factors (TLin, TLou, TPin and TVis) exceed 5.0. This indicates that 30% of cloudless sky conditions can be considered turbid to very turbid.