| 英文摘要: | In this study, radiosonde observations from seven sites in Saudi Arabia for the period 1985 to 2016 were utilized to investigate the interannual, monthly, and seasonal variations and trends of precipitable water vapour (PWV). The magnitudes of these trends have been characterized and tested using the Mann-Kendall (MK) rank statistics at different significance levels. A significant decrease in the annual mean PWV by about 7% is found for the entire period. A seasonal cycle of PWV with a maximum during summer time and a minimum during winter has been found and can be mostly attributed to the variations of air temperature. On a monthly basis, the PWV values revealed a decreasing trend with the rate of decrease ranging between 0.47 and 2.6 mm per 32 years. There was a decrease in PWV in all the seasons, but it was only significant for the spring season, when it was the highest (1.79 mm per 32 years).
Power spectra analyses using the Fourier Transform (FT) technique were carried out for the period 1985-2016 to investigate the periodicities in the PWV time series. Several long, mid, and short-term periodicities were recognized. Short-term periodicities such as one year, six months, three months, and four months were found. On the other hand, long and mid term periodicities such as 10.8-11 years, 1.7 years, and 1.3 years were detected. The obtained periodicities are similar to those reported by several investigators and found in solar, interplanetary, and cosmic ray parameters. The spectral results suggest that the obtained PWV periodicities in Arabian Peninsula are, possibly, related to the solar activities, as well as, the effect of terrestrial meteorological phenomena.
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