佛山地区有限高度视线无云概率的计算

CALCULATION OF PROBABILITY OF CLOUD-FREE LINES-OF-SIGHT AT GIVEN HEIGHT IN FOSHAN

本文绘出了适用于世界任何地区的地面到任意有限高度上视线无云概率的计算方法和视线无云持续概率与再现概率的计算方法，并利用我国佛山地区30年的地面常规云观测资料计算了佛山地区有限高度视线无云概率、视线无云持续概率与视线无云再现概率，得到以下结论：（1）视线无云概率随高度的增加而减小，随视角的增大而增大。（2）视线无云持续概率和视线无云再现概率随高度的增加和滞后时间的延长而减小。（3）视线无云再现概率总等于或大于视线无云持续概率。

Based on Lund and Shanklin's work, methods of calculating probability ofCloud -Free Lines -Of -Sight (PCFLOS)、 Persistence Probability of Cloud -Free LinesOf -Sight (PPCFLoS) and Recurrence Probability of Cloud -free Lines -Of-Sight (RPCF-LOS) at given height are present. PCFLOS,PPCFLOS'RPCFLoS are calculated in Foshanby conventional observational data from 1961 to 1990 and three conclusions are obtained:(1)The higher the height and the lower the angle of view,the smaller the PCFLOS.(2)PPCFLOS and RPCFLOS reduce with the increase of height and lag time.(3)RPCFLOS are always equal to or larger than PPCFLOS at lag time.