The book essentially covers: Temporal and spatial distribution of total precipitable water (TPW), derived from ATOVS measurements and radiosonde profiling across different geographical regions and climatic seasons in Peninsular Malaysia. Distribution of TPW at different altitudes (atmospheric layers) namely upper, lower and middle layers. Computation of empirical models correlating TPW at middle and higher atmospheric layers with that of the lower layer in order to establish possible interlayer correlation. Development of models to estimate/predict layered (lower, middle and upper) and TPW using precipitable water obtained from ATOVS satellite data and surface meteorological data (temperature, pressure and relative humidity). Development and comparison of artificial neural networks (ANN) models with the multiple linear regression (MLR) models. Contrasting precipitable water data from ATOVS with radiosonde observations, portrays the former as suitable for studies on TPW. The two sources of water vapour profiles agreed reasonably well, both seasonally and spatially across the different geographical regions and climatic seasons in Peninsular Malaysia. The developed MLR based models provide excellent predictive capabilities with seasonal and spatial dependency, especially during the northeast monsoon and northwards across Peninsular Malaysia.