Tuesday, 11 January 2005
Assessment of PCM Results for Predictions of Climate Changes in the Caribbean
A validation exercise for the global circulation model Parallel Climate Model (PCM) using the “Business as Usual” (BAU) scenario, was performed over the Caribbean region. The chosen period of analysis was the early rainy season (ERS) for the region, which comprises the months from May through July. The ERS of 1998 was a dry season due to the development of a La Nina event, with SSTs over the North Atlantic having the strongest influence for this lower-than-average precipitation period. The 24 year precipitation climatology of the Caribbean basin shows a strong correlation between dry early rainfall seasons with La Niña events. When comparing Sea Surface Temperatures (SSTs) from the PCM and the Atmospheric Model Intercomparison Project (AMIP) over the Caribbean basin, it was clear that the PCM was unable to capture the La Nina influence on precipitation over the region. The National Centers for Environmental Prediction (NCEP) re-analysis data was used to validate the PCM atmospheric variables. NCEP data, altogether with simulated SSTs ocean data, evidenced the deviations of the PCM global model on the ocean interface over the Caribbean basin, in which simulated SSTs anomalies (SSTAs) had negatives values whereas positive SSTAs were actually observed. Also, during the course of the early rainy season, the SSTAs and the vertical wind shear dominated over the positive/negative moisture advection with regard to precipitation variability both in the Main Development Region (MDR) and the Gulf of Mexico. The PCM coupled model followed this behavior at first, but it showed deviations by the middle and end of the early rainy season.