Monday, 14 January 2002: 5:15 PM
How are Decade-Scale Precipitation Variations Reflected in the Daily Precipitation Record?
The presence of decade-scale variations in the climatic records has been a subject of research for a number of years. Research has also established that even small decade-scale changes in precipitation can have large impacts on surface water resources. To better identify the impact of decade-scale variations in precipitation on surface water, it is necessary to determine the changes in daily precipitation characteristics that produce the decade-scale variations, because it is the daily precipitation and weather that control surface runoff, infiltration, soil water storage and evapotranspiration. This study uses a 100+ year record of daily precipitation to investigate this question. The location of interest is central Oklahoma. Previous studies based on divisional precipitation records showed that this region experienced an increase in precipitation over the last two decades of the 20th century. The Kingfisher National Weather Service (NWS) cooperative station in Kingfisher County, Oklahoma, is the source for the daily data. A preliminary analysis of the annual precipitation identified the beginning of the decade-scale precipitation increase. This decade-scale period of increased precipitation is called the wet period. The annual, monthly and daily precipitation statistics, including frequency distributions, of the wet period are compared to the remainder of the record earlier in the century. Based on these findings, the relevance of the change in daily precipitation characteristics during the wet period for surface water is discussed. Also, the most appropriate analysis approach, daily (process based) versus statistical (lumped), to linking decade-scale precipitation variations to surface water is identified. These last considerations are critical to the practical relevance and application of decade-scale precipitation variations to related societal water resource problems.