Time Series Analysis of 20 Years of Hourly Precipitation in Southwest Michigan

Abstract

Hourly precipitation data from Oshtemo Township, Michigan, located approximately 55 km east of the lee shore of Lake Michigan, for the period of April 1980 through March 2000 were examined. Diurnal analysis of precipitation as well as time series analysis of precipitation were performed on the study period. An overall nocturnal maximum in the mean accumulation of precipitation was detected during the 2-hour periods before 2000 LST and 2200 LST. Elevated spring and fall accumulations were responsible for this evening maximum. Elevated summer and winter accumulations were responsible for a weak secondary morning maximum. An overall morning maximum in the mean precipitation hours was detected during the 2-hour period before 1000 LST. ARIMA modeling verified that both precipitation accumulations and counts, for all times of the day, were significant at the 5% level. A storm event model was developed from the time series, the resulting values of which can be used as input in mesoscale climate, hydrological, and agricultural computer models: the mean pulse duration was 2.44 hours; the mean interlude between pulses was 37.64 hours; the mean event accumulation was 4.1 mm; and the mean rate was 1.8 mm / hr. Finally, inter-annual analysis performed for the period of 1981 to 1999 showed that there was no statistically significant change in precipitation over the period.