Temporal and Spatial Variability of Annual Rainfall Patterns in Guanacaste, Costa Rica Steyn, Douw G.; Moisseeva, Nadya; Harari, Ofir; Welch, William J.
We analyze a body of rainfall data covering 38 years from five meteorological stations in the Nicoya Peninsula of the Guanacaste Province, Costa Rica. The purpose of the analysis is to uncover spatial and temporal variability of rainfall in order to support research into water and sustainability under the FuturAgua project. We use a variety of statistical analysis and modelling techniques. The analysis uncovers a relatively suppressed spatial pattern of rainfall. Rainfall totals for periods shorter than two weeks are dominated by strong stochastic variability, while longer totalizing periods reveal systematic variation. Monthly totals show the strong double peak, and associated midsummer drought that has been previously reported. The annual cycle can be efficiently captured by a double Gaussian model. A simple application of this model to individual years shows large inter- annual variability, and a strong dependence of the second rainfall peak on the Oceanic Niño Index (ONI). A Bayesian analysis confirms the appropriateness of the double Gaussian model, and quantifies the strength of the dependence on ONI. We discuss the implications of our statistical analyses for research under the FuturAgua project.
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