Calculation of Probability of Cloud-Free Lines-of-Sight at given heights in Foshan, China

Based on Lund and Shanklin's work (1972), methods of calculating Probabilit y of Cloud-Free Lines-of-Sight (PCFLOS), Persistence Probability of Cloud-F ree Lines-of-Sight (PPCFLOS) and Recurrence Probability of Cloud-free Lines -of-Sight (RPCFLOS) at given heights are presented. PCFLOS, PPCFLOS and RPC FLOS are calculated in Foshan, China by conventional observation data from 1961 to 1990. The conclusions are: (1) The higher the elevations, the smaller the PCFLOS and the larger the vi ew angles, the larger the PCFLOS. (2) PPCFLOS and RPCFLOS decrease with the increase of elevation and the del ay of time. (3) RPCFLOS is always equal to or larger than PPCFLOS at lag times.