Modeling and Simulation of Spatial and Temporal Precipitation Patterns in Coastal Mountainous Regions – The Case of Northwestern Colombia

Regional and local weather patterns are strongly affected by macroclimatic phenomena. In tropical South America, hydroclimatological behavior is affected by such factors as the meridional oscillation of the Intertropical Convergence Zone, the dynamics of Pacific and Atlantic oceans, the Amazon jungle, and the orographic barriers of the Andes mountains. Interactions between these factors at different space and time scales are complex and non-linear, in particular for the region of northwestern Colombia, one of the rainiest regions of the world. In addition, the El Niño/Southern Oscillation (ENSO) phenomenon is recognized as the dominant mode of inter-annual climate variability in the region (e.g., ENSO variability explains about 50% of the observed variance of Colombian hydrology beyond the annual cycle when a linear relationship is assumed). To capture these non-linear interactions and their impact on precipitation, CSU’s Regional Atmospheric Modeling System (RAMS) has been used to perform representative simulations of precipitation cycles in Colombia. CSU-RAMS has been implemented using a nested set of two grids. Input data for initial and lateral boundary conditions were from National Center for Environmental Prediction reanalysis products. Results illustrate the challenges in modeling these non-linear interactions, especially the significant impact of local relief, and the great importance of capturing the diurnal cycle in defining the magnitude and the spatial and temporal patterns of precipitation. It is expected that this physically-based modeling technique will lead to increased understanding of hydroclimatic patterns that can be used for regional and local socio-economic planning and policy making in the contexts of hazard mitigation and optimal use of water resources in Colombia.