An investigation of seasonal precipitation patterns for rainfed agriculture in the Southeastern region of the United States

Over the last two decades, signs of precipitation irregularity were frequently reported across the Southeastern United States (US). Even though the region receives a relatively high annual precipitation, the precipitation events are not equally distributed in the time and space. Hence, rainfed agriculture, a common practice in the region is threatened by changes in precipitation frequencies during the crop growing seasons. With this situation, a better understanding of the actual patterns of precipitation irregularity is needed to support the local agriculture. This study uses a spatial regionalization approach to delineate precipitation regions for an area spanning the states of South Carolina, North Carolina, and Georgia. The data used include time-series of seasonal precipitation totals and seasonal numbers of precipitation events > 5mm over the period 1960-2017. A regionalization method which combines principal components and cluster analyses was applied to 208 precipitation stations selected across the study region. Finally, three precipitation regions were delineated based on statistics and similarity criteria. A comparative analysis of these three regions shows significant differences in the seasonal precipitation totals and the seasonal number of precipitation events. In addition, the differences were examined using a probabilistic approach. As a result, tables of probabilities and seasonal precipitation characteristics (precipitation totals and number of events > 5 mm) were generated for each region. These tables could provide information about the chances of precipitation deficits or excesses relatively to a crop and henceforth be useful for agricultural water use planning.