Using Climate Variability to Predict the Inter-annual Variability of Precipitation and to Estimate the Persistence of Climate Extremes for Urban Areas and Regions within the United States

Links between climate variability and total precipitation in several regions and urban areas throughout the United States are developed using one of nearly thirty global climate indices tested. Precipitation data from over 1200 stations are obtained from the United States Historical Climatology Network maintained by the National Climate Data Center, NOAA. All data are temporally averaged over an extended period (up to five years), and attempts are made to correlate the data with climate indices averaged over a period of equal length using lag times also up to five years. The length of the period and the lag time are varied until the highest correlation is achieved. The index that demonstrates the best correlation with precipitation is identified for each urban area and used to create regions that are dominated by a particular index; strong correlations (r2 values > 0.70) were found to exist in all regions. A map of the United States is constructed that displays the spatial distribution of each region. The final results of this study will not only allow a greater understanding of the major mechanisms that are responsible for inter-annual rainfall variability throughout the United States, but will also allow improved predictability of precipitation over multiple time scales. In addition, the ability to predict total rainfall for periods greater than one year will allow an estimate of the persistence of trends and extreme events, such as periods of drought or above-average rainfall, to be made in advance with a lead time that is dependent on the lag times used to create each correlation. An example related to the California Drought is given.