Adjustment of temperature and rainfall records for site changes



Methods are presented for estimating the effect of known site changes on temperature and rainfall measurements. Parallel cumulative sums of seasonally adjusted series from neighbouring stations are a useful exploratory tool for recognizing site-change effects at a station that has a number of near neighbours. For temperature data, a site-change effect can be estimated by a difference between the target station and weighted mean of neighbouring stations, comparing equal periods before and after the site change. For rainfall the method is similar, except for a logarithmic transformation. Examples are given. In the case of isolated stations, the estimation is necessarily more subjective, but a variety of graphical and analytical techniques are useful aids for deciding how to adjust for a site change.