The current decade-scale precipitation fluctuation in the Southern Great Plains

Decade-scale precipitation fluctuations have been documented and analyzed to further the understanding of climate variability and predictability. These fluctuations also touch many aspects of our society that depend on trends and changes in the weather, such as drought and flood preparedness, agriculture, transportation and energy production, to name a few. This study investigates the characteristics of the latest decade-scale precipitation fluctuation in the Southern Great Plains. The magnitude and geographical extent of this fluctuation are determined and the potentials for agricultural production are discussed.

The precipitation fluctuation is studied based on monthly and annual precipitation records of selected weather stations and climate divisions in the Southern Great Plains. The length of the historical precipitation records is about 100 years for the weather stations and about 85 years for the climate divisions. High frequency annual fluctuations are removed from the records by use of a moving-average filter. The intensity and distribution of severe weather during the fluctuation are studied and reported separately. Only the decade-scale characteristics of the precipitation fluctuation are reported here. The geographic extent of the study includes the states of Colorado, Kansas, Missouri, New Mexico, Oklahoma, Arkansas, Texas and Louisiana. The Rocky Mountain regions of Colorado and New Mexico are subject to a different climate regime than the plains and are not included in this study.

In a first step, the spatial extent and magnitude of the precipitation fluctuations are determined based on the climate division data of all eight states. The amplitude of the latest fluctuation is compared to those of previous fluctuations this century for each climate division. The results are graphically displayed by use of a Geographic Information System. Preliminary results suggest that the fluctuation covers a large portion of the Southern Great Plains and the fluctuation appears to be strongest in the Oklahoma-Kansas region.

In a second step, the fluctuation is analyzed for selected weather stations and climate divisions in Oklahoma. The results indicate that the fluctuation appears to begin in early to mid 1980's and reach its peak in mid 1990's and the amplitude appears to be the largest on record. This is further supported by a general rising trend in precipiation normals in the last half of the century. A further analysis of the annual distribution suggests that the increased precipitation is not uniformly distributed throughout the year.

The recurrence of decade-scale precipitation fluctuations and the seasonal distribution of the increased precipitation suggest that agriculture in the Southern Great Plains, which is primarily based on dry-land farming and irrigation, could benefit from this climate information. Agricultural planning and management strategies could be developed to diversify and increase production during the seasons with increased precipitation.