TOPOGRAPHICAL EFFECTS ON THE DISTRIBUTIONS OF RAINFALL AND O-18 DISTRIBUTIONS - A CASE IN MIYAKE ISLAND, JAPAN

In this paper, we try to calculate precipitation in Miyake Island, Jap an. In order to know the temporal and spatial variations of precipitat ion, we have set 15 rain gauges randomly in the island to collect the monthly precipitation data since June 1994. It is found that the preci pitation is very different from point to point. First, we used statist ical methods to get the correlations between the monthly precipitation at our survey points and that at the weather station. Next, regressio n analyses were used to establish formulae to calculate precipitation as a function of altitude, aspect of the geomorphological surface and wind direction. Based on these results, distributions of monthly and y early precipitation and delta(18)O over the island were assessed. The results show that landscape patterns strongly influence precipitation distribution over the island, with the highest precipitation being fou nd on the windward side, about 400-600 m above sea level. Even at plac es at the same altitude, the precipitation was different because of th e aspect of the landscape. At the same time, altitude effects for delt a(18)O on both the windward and leeward sides were -0.10 parts per tho usand/100 m and -0.15 parts per thousand/100 m, respectively. Comparin g with the distribution of precipitation distribution, it was also fou nd that delta(18)O for the windward and leeward sides was different fr om that for precipitation, which means that both topographical effects must be considered separately. (C) 1998 John Wiley & Sons, Ltd.