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Precipitation climatologies for the period 1961–1990 were generated for all climatic regions of Costa Rica using an irregular rain-gauge observational network comprised by 416 rain-gauge stations. Two sub-networks were defined: a high temporal resolution sub-network (HTR), including stations having at least 20 years of continuous records during the study period (157 in total); and a high spatial resolution sub-network (HSR), which includes all HTR-stations plus those stations with less than 20 years of continuous records (416 in total). Results from the kriging variance reduction efficiency (KRE) objective function between the two sub-networks, show that ordinary kriging (OK) is unable to fully explain the spatio-temporal variability of precipitation within most climatic regions if only stations from the HTR sub-network are used. Results also suggests that in most cases, it is beneficial to increase the density of the rain-gauge observational network at the expense of temporal fidelity, by including more stations even though their records may not represent the same time step. Thereafter, precipitation climatologies were generated using seven deterministic (IDW, TS2, TS2PARA, TS2LINEAR, TPS, MQS and NN) and two geostatistical (OK and KED) interpolation methods. Performance of the various interpolation methods was evaluated using cross validation technique, selecting the mean absolute error (MAE) and the root-mean square error (RMSE) as agreement metrics. Results suggest that IDW is marginally superior to OK and KED for most climatic regions. The remaining deterministic methods however, considerably deviate from IDW, which suggests that these methods are incapable of properly capturing the true-nature of spatial precipitation patterns over the considered climatic regions. The final generated IDW climatology was then validated against the Global Precipitation Climatology Centre (GPCC), Climate Research Unit (CRU) and WorldClim datasets, in which overall spatial and temporal coherence is considered satisfactory, giving assurance about the use this new climatology in the development of local climate impact studies.

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This study aimed to assess the impacts of climate change on streamflow characteristics of five tropical catchments located in Costa Rica. An ensemble of five General Circulation Models (GCMs), namely HadGEM2-ES, CanESM2, EC-EARTH, MIROC5, MPI-ESM-LR dynamically downscaled by two Regional Climate Models (RCMs), specifically HadRM3P and RCA4, was selected to provide an overview of the impacts of different climate change scenarios under Representative Concentration Pathways (RCPs) 2.6, 4.5 and 8.5 using the 1961–1990 baseline period. The GR2M hydrological model was used to reproduce the historical monthly surface runoff patterns of each catchment. Following calibration and validation of the GRM2 model, the projected impact of climate change on streamflow was simulated for a near-future (2011–2040), mid-future (2041–2070) and far-future (2071–2100) for each catchment using the bias-corrected GCM-RCM multimodel ensemble-mean (MEM). Results anticipate wetter conditions for all catchments in the near-future and mid-future periods under RCPs 2.6 and 4.5, whereas dryer conditions are expected for the far-future period under RCP 8.5. Projected temperature trends indicate consistently warmer conditions with increasing radiative forcing and future periods. Streamflow changes across all catchments however are dominated by variations in projected precipitation. Wetter conditions for the near-future and mid-future horizons under RCPs 2.6 and 4.5 would result in higher runoff volumes, particularly during the late wet season (LWS). Conversely, dryer conditions for the far-future period under RCP8.5 would result in considerably lower runoff volumes during the early wet season (EWS) and the Mid-Summer Drought (MSD). In consequence, projected seasonal changes on streamflow across all catchments may result in more frequent flooding, droughts, and water supply shortage compared to historical hydrological regimes.

Actualmente, los datos textuales constituyen una parte fundamental de las bases de datos de todo el mundo y uno de los mayores desafíos ha sido la extracción de información útil a partir de conjuntos grandes de documentos de texto. La literatura existente sobre métodos para resolver este problema es muy extensa, sin embargo, los métodos estadísticos (que utilizan métricas de similitud sobre vectores de palabras) han mostrado resultados muy favorables en el campo de la minería de texto durante los últimos 25 años. Adicionalmente, otros modelos han surgido como una prometedora alternativa para lograr reducción dimensional e incorporación de la semántica en la clasificación de documentos, tal como el modelado de temas. Este proyecto se enfoca en la evaluación de técnicas de representación y medidas de similitud de texto (Coseno, Jaccard y Kullback-Leibler) usando el algoritmo de Vecinos más Cercanos (KNN por sus siglas en inglés), con el fin de medir la efectividad del modelado de temas para reducción dimensional al clasificar texto. Los resultados muestran que la versión más tradicional del vector de palabras y la similitud Jaccard superaron al resto de las combinaciones en la mayoría de los casos de uso. Sin embargo, el análisis estadístico mostró que no hubo una diferencia significativa entre la exactitud obtenida al usar representaciones generadas por la Asignación de Dirichlet Latente (técnica de modelado de temas más conocida como LDA por sus siglas en inglés), y la obtenida usando técnicas tradicionales de clasificación de texto. LDA logró abstraer miles de palabras en menos de 60 temas para el primer conjunto de pruebas. Experimentos adicionales sugieren que el modelado de temas puede llegar a lograr un mejor rendimiento al ser usado para clasificar textos cortos y al incrementar el número de temas permitidos al momento de generar el modelo.