Observed changes in the frequency of heavy precipitation events in the southern climate region and policy implications

It is well known that an increased Global average temperature increases the water holding capacity of the atmosphere, with implications for the distribution and intensity of precipitation. The Intergovernmental Panel on Climate Change (IPCC) suggests that an increase in the frequency of heavy precipitation events is very likely, in conjunction with a general increase in the frequency of extreme events (floods/drought). Recent extreme rainfall events in parts of the Southern US have made salient the Societal and Economic impacts of these extremes. Flooding remains one of the number one weather related killers in the United States, and causes significant damage to infrastructure. This work investigates changes in the frequency of moderate, heavy and very heavy 1-day precipitation events using the Cooperative Raingauge network for the States of Oklahoma, Texas, Arkansas, Louisiana, Mississippi and Tennessee. Fixed precipitation thresholds are defined, which vary dependant on location, annual precipitation amounts and approximate return periods. Both individual station and Climate Division trends are examined over temporal periods ranging from 1900-2009. Multiday trends in each State Climate Division between 1-14 days are also examined. Preliminary results indicate that nearly all stations exhibit increased frequencies of moderate (1.5-3 inch/day) precipitation, with mixed results for higher thresholds. Statistically significant increasing trends are spatially diverse, but tend to be clustered in East and Central Texas north into Central Oklahoma, and along the Gulf Coast. Further results will be discussed, along with likely implications for local decision makers in forming adaptation and mitigation strategies.