Characterising droughts in Central America with uncertain hydro-meteorological data

Central America is frequently affected by droughts that cause significant socio-economic and environmental problems. Drought characterisation, monitoring and forecasting are potentially useful to support water resource management. Drought indices are designed for these purposes, but their ability to characterise droughts depends on the characteristics of the regional climate and the quality of the available data. Local comprehensive and high-quality observational networks of meteorological and hydrological data are not available, which limits the choice of drought indices and makes it important to assess available datasets. This study evaluated which combinations of drought index and meteorological dataset were most suitable for characterising droughts in the region. We evaluated the standardised precipitation index (SPI), a modified version of the deciles index (DI), the standardised precipitation evapotranspiration index (SPEI) and the effective drought index (EDI). These were calculated using precipitation data from the Climate Hazards Group Infra-Red Precipitation with Station (CHIRPS), the CRN073 dataset, the Climate Research Unit (CRU), ECMWF Reanalysis (ERA-Interim) and a regional station dataset, and temperature from the CRU and ERA-Interim datasets. The gridded meteorological precipitation datasets were compared to assess how well they captured key features of the regional climate. The performance of all the drought indices calculated with all the meteorological datasets was then evaluated against a drought index calculated using river discharge data. Results showed that the selection of database was more important than the selection of drought index and that the best combinations were the EDI and DI calculated with CHIRPS and CRN073. Results also highlighted the importance of including indices like SPEI for drought assessment in Central America.Universidad de Costa Rica/[805-B0-810]/UCR/Costa RicaUniversidad de Costa Rica/[805-A9-532]/UCR/Costa RicaUniversidad de Costa Rica/[805-B3-600]/UCR/Costa RicaUniversidad de Costa Rica/[805-B0-065]/UCR/Costa RicaUniversidad de Costa Rica/[805-B3-413]/UCR/Costa RicaUniversidad de Costa Rica/[805-B4-227]/UCR/Costa RicaUniversidad de Costa Rica/[805-B4-228]/UCR/Costa RicaUniversidad de Costa Rica/[805-B5-295]/UCR/Costa RicaUppsala University/[54100006]//SueciaMarie Curie Intra-European Fellowship/[No.329762]//EuropaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Físic

Characteristic atmospheric states during mid‑summer droughts over Central America and Mexico

Open AccessAnnual precipitation over Central America and large areas of Mexico is typically characterised by its bimodal distribution, with a precipitation minimum in July to August that occurs between two separate maxima from May to July and August to October. Several theories have been proposed to explain this phenomenon, which is often termed the mid-summer drought (MSD), but most fail to address the diferent characteristics associated with individual MSD events. Here, a regression-based approach is used to detect and quantify the annual and climatological MSD signature over Central America and Mexico. This approach has been evaluated and shown to be robust for various datasets with diferent spatial resolutions. It was found that in the southeast of the Mexico/Central America region, MSDs start earlier and end later than elsewhere, and are thus longer in duration. However, the coast of the Gulf of Mexico, Cuba, and large areas of Central America, exhibit climatologically stronger MSDs. Changes in precipitation, brought about by the interaction between reversals of the onshore/ofshore winds and orographic forcing associated with the steep mountainous terrain, have also been shown to be signifcant factors in the timing of MSD occurrences, ofering support for a combined theory of large-scale dynamics and regional forcing. Using self-organising maps (SOMs) as an analysis tool, it was found that MSD events over the domain display strong spatial variability. The MSDs over the domain also generate distinct signatures and may be forced by particular mechanisms. We found that El Niño-Southern Oscillation (ENSO) could be a potential classifer for the SOM identifed atmospheric states, based on the correspondence of MSD occurrences with ENSO phasesLa precipitación anual sobre Centroamérica y grandes áreas de México se caracteriza típicamente por su distribución bimodal, con un mínimo de precipitación en julio a agosto que ocurre entre dos máximos separados de mayo a julio y de agosto a octubre. Se han propuesto varias teorías para explicar este fenómeno, que a menudo se denomina sequía de mediados de verano (TME), pero la mayoría no aborda las diferentes características asociadas con los eventos de TME individuales. Aquí, se utiliza un enfoque basado en regresión para detectar y cuantificar la firma anual y climatológica de MSD en Centroamérica y México. Este enfoque ha sido evaluado y ha demostrado ser robusto para varios conjuntos de datos con diferentes resoluciones espaciales. Se encontró que en el sureste de la región de México / Centroamérica, los TME comienzan antes y terminan más tarde que en otros lugares y, por lo tanto, tienen una duración más prolongada. Sin embargo, la costa del Golfo de México, Cuba y grandes áreas de Centroamérica exhiben TME climatológicamente más fuertes. Los cambios en la precipitación, provocados por la interacción entre las reversiones de los vientos en tierra / de tierra y el forzamiento orográfico asociado con el terreno montañoso escarpado, también han demostrado ser factores significativos en el momento de la ocurrencia de TME, ofreciendo apoyo para una teoría combinada de grandes dimensiones. -Dinámica de escala y forzamiento regional. Utilizando mapas autoorganizados (SOM) como herramienta de análisis, se encontró que los eventos de MSD en el dominio muestran una fuerte variabilidad espacial. Los MSD sobre el dominio también generan firmas distintas y pueden ser forzados por mecanismos particulares. Descubrimos que El Niño-Oscilación del Sur (ENOS) podría ser un clasificador potencial para los estados atmosféricos identifcados por la MOS, con base en la correspondencia de las ocurrencias de MSD con las fases del ENOS.Universidad de Melbourne, AustraliaUniversidad de Tasmania, AustraliaUniversidad de Dalhousie, CanadáUniversidad Nacional, Costa RicaDepartamento de Físic