Estimation of average annual rainfall over the Port Phillip region of Victoria

There is shown to be little correlation between average annual rainfall and elevation but consideration of physical principles involved in rainfall production indicates that other factors may have considerable influence on the amount received at a particular location. Orographic features increase the rainfall over favourably located areas and cause a decrease over others whilst elsewhere the distance from the sea may be the most important factor over the whole region the bulk of the rainfall is associated with a surface wind having a westerly component. Graphical methods of estimating the influence of each of these factors on average annual rainfall have been developed. Each correction is applied in turn and the resultant estimates are in most cases within 10 per cent of the observed values. Modification of the relationships developed would be necessary before the method could be applied to other regions.