| Abstract: | Based on Lund and Shanklin's work (1972), methods of calculating Probability of Cloud-FreeLines-of-Sight (PCFLOS). Persistence Probability of Cloud Free Lines of-Sight (PPCFLOS) and Recurrence Probability of Cloud-free Lines-of-Sight (RPCFLOS) at given heights are presented. PCFLOS,PPCFLOS and RPCFLOS are calculated in Foshan. China by conventional observation data from 1961 to1990. The conclusions are:(1) The higher the elevations, the smaller the PCFLOS and the larger the view angles, the larger thePCFLOS.(2) PPCFLOS and RPCFLOS decrease with the increase of elevation and the delay of time.(3) RPCFLOS is always equal to or larger than PPCFLOS at lag times. |
