Review

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Abstract
This research aims to calculate the amount of precipitable water vapor in the atmosphere of
Thailand. From upper air checking data, relative humidity and temperature. The data were collected
continuously from four meteorological monitoring stations, Chiang Mai, Ubon Ratchathani, Bangkok and
Songkhla station during 1992-2007. The data from this investigation were used to predict a mathematical
model to make correlations to the precipitable water with surface climatological data, relative humidity and
temperature. Results show that precipitable water vapor at Chiang Mai, Ubon Ratchathani and Bangkok
station were higher in the rainy season and lower in the dry season. The precipitable water vapor in
Songkhla station was quite constant throughout the year. The precipitable water vapor obtained from upper
air corrended to value of the model. Difference in the Root Mean Square Error (RMSE) was 0.354 cm.
After calculation the amount of precipitable water vapor from surface data at 85 meteorological stations
nationwide, it varied from 2.431 cm to 6.146 cm. The result showed that the precipitable water vapor were
relative low in the dry (November to March) and relative high in the rainy season (April to October) with
an average was 4.571±0.107 cm per year.
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