Uncertainties in climate change projections and regional downscaling: implications for water resources management

Climate change is expected to have a large impact on water resources worldwide. A major problem in assessing the potential impact of a changing climate on these resources is the difference in spatial scale between available climate change projections and water resources management. Regional climate models (RCMs) are often used for the spatial disaggregation of the outputs of global circulation models. However, RCMs are time-intensive to run and typically only a small number of model runs is available for a certain region of interest. This paper investigates the value of the improved representation of local climate processes by a regional climate model for water resources management in the tropical Andes of Ecuador. This region has a complex hydrology and its water resources are under pressure. Compared to the IPCC AR4 model ensemble, the regional climate model PRECIS does indeed capture local gradients better than global models, but locally the model is prone to large discrepancies between observed and modelled precipitation. It is concluded that a further increase in resolution is necessary to represent local gradients properly. Furthermore, to assess the uncertainty in downscaling, an ensemble of regional climate models should be implemented. Finally, translating the climate variables to streamflow using a hydrological model constitutes a smaller but not negligible source of uncertainty

Basic theory behind parameterizing atmospheric convection

Last fall, a network of the European Cooperation in Science and Technology (COST), called “Basic Concepts for Convection Parameterization in Weather Forecast and Climate Models” (COST Action ES0905; see http://w3.cost.esf.org/index.php?id=205&action_number=ES0905), organized a 10-day training course on atmospheric convection and its parameterization. The aim of the workshop, held on the island of Brac, Croatia, was to help young scientists develop an in-depth understanding of the core theory underpinning convection parameterizations. The speakers also sought to impart an appreciation of the various approximations, compromises, and ansatz necessary to translate theory into operational practice for numerical models

Impacts of land use on the hydrological response of tropical Andean catchments

Changes in land use and land cover are major drivers of hydrological alteration in the tropical Andes. However, quantifying their impacts is fraught with difficulties because of the extreme diversity in meteorological boundary conditions, which contrasts strongly with the lack of knowledge about local hydrological processes. Although local studies have reduced data scarcity in certain regions, the complexity of the tropical Andes poses a big challenge to regional hydrological prediction. This study analyses data generated from a participatory monitoring network of 25 headwater catchments covering three of the major Andean biomes (páramo, jalca, and puna), and link their hydrological responses to main types of human interventions (cultivation, afforestation and grazing). A paired catchment setup was implemented to evaluate the impacts of change using a “trading space-for-time” approach. Catchments were selected based on regional representativeness and contrasting land use types. Precipitation and discharge have been monitored and analysed at high temporal resolution for a time period between 1 and 5 years. The observed catchment responses clearly reflect the extraordinarily wide spectrum of hydrological processes of the tropical Andes. They range from perennially humid páramos in Ecuador and northern Peru with extremely large specific discharge and baseflows, to highly seasonal, flashy catchments in the drier punas of southern Peru and Bolivia. The impacts of land use are similarly diverse and their magnitudes are a function of catchment properties, original and replacement vegetation, and management type. Cultivation and afforestation consistently affect the entire range of discharges, particularly low flows. The impacts of grazing are more variable, but have the largest effect on the catchment hydrological regulation. Overall, anthropogenic interventions result in increased streamflow variability and significant reductions in catchment regulation capacity and water yield, irrespective of the hydrological properties of the original biome

Glaciers in Patagonia: Controversy and prospects

Lately, glaciers have been subjects of unceasing controversy. Current debate about planned hydroelectric facilitiesa US$7- to$10-billion megaprojectin a pristine glacierized area of Patagonia, Chile [Romero Toledo et al., 2009; Vince, 2010], has raised anew the matter of how glaciologists and global change experts can contribute their knowledge to civic debates on important issues. There has been greater respect for science in this controversy than in some previous debates over projects that pertain to glaciers, although valid economic motivations again could trump science and drive a solution to the energy supply problem before the associated safety and environmental problems are understood. The connection between glaciers and climate changeboth anthropogenic and naturalis fundamental to glaciology and to glaciers\u27 practical importance for water and hydropower resources, agriculture, tourism, mining, natural hazards, ecosystem conservation, and sea level [Buytaert et al., 2010; Glasser et al., 2011]. The conflict between conservation and development can be sharper in glacierized regions than almost anywhere else. Glaciers occur in spectacular natural landscapes, but they also supply prodigious exploitable meltwater. © 2012. American Geophysical Union. All Rights Reserved

Transporte de humedad y variaciones estacionales en la composición isotópica estable de la lluvia en el páramo centroamericano y andino durante las condiciones de El Niño (2015-2016)

Los sistemas de pastizales tropicales de gran altitud, llamados Páramo, brindan servicios ecosistémicos esenciales como el almacenamiento y el suministro de agua para las áreas circundantes y de tierras bajas. Los sistemas de páramo están amenazados por los cambios climáticos y de uso del suelo. Los procesos de generación de lluvia y las vías de transporte de humedad que influyen en la precipitación en el Páramo no se conocen bien, pero se necesitan para estimar el impacto de estos cambios, particularmente durante las condiciones de El Niño, que afectan en gran medida las condiciones hidrometeorológicas en las regiones tropicales. Para llenar este vacío de conocimiento, presentamos un análisis de isótopos estables de las muestras de lluvia recolectadas diariamente o semanalmente entre enero de 2015 y mayo de 2016 durante el evento de El Niño más fuerte registrado en la historia (2014-2016) en dos regiones de Páramo de América Central (Chirripó, Costa Rica) y el norte de los Andes (Cajas, sur de Ecuador). Se utilizaron composiciones isotópicas para identificar cómo los procesos de generación de lluvia (convectiva y orográfica) cambian estacionalmente en cada sitio de estudio. Se usó el análisis de trayectoria de masa de aire híbrido de modelo de trayectoria integrada lagrangiana de partícula única (HYSPLIT) para identificar rutas preferenciales de transporte de humedad a cada sitio de Páramo. Nuestros resultados muestran la fuerte influencia de los vientos alisios del noreste para transportar la humedad del Mar Caribe a Chirripó y el jet sudamericano de bajo nivel para transportar la humedad del bosque amazónico a Cajas. Estas contribuciones de humedad también se relacionaron con la formación de lluvia convectiva asociada con el paso de la Zona de Convergencia Intertropical sobre Costa Rica y Ecuador durante las estaciones más húmedas y con la precipitación orográfica durante las temporadas de transición y más secas. Nuestros hallazgos brindan información básica esencial para futuras aplicaciones de investigación de isótopos estables al agua como trazadores de procesos de generación de lluvia y transporte en el Páramo y otros ecosistemas montanos en los trópicos.High‐elevation tropical grassland systems, called Páramo, provide essential ecosystem services such as water storage and supply for surrounding and lowland areas. Páramo systems are threatened by climate and land use changes. Rainfall generation processes and moisture transport pathways influencing precipitation in the Páramo are poorly understood but needed to estimate the impact of these changes, particularly during El Niño conditions which largely affect hydrometeorological conditions in tropical regions. To fill this knowledge gap, we present a stable isotope analysis of rainfall samples collected on a daily to weekly basis between January 2015 and May 2016 during the strongest El Niño event recorded in history (2014‐2016) in two Páramo regions of Central America (Chirripó, Costa Rica) and the northern Andes (Cajas, south Ecuador). Isotopic compositions were used to identify how rainfall 

High-resolution hydrometeorological data from a network of headwater catchments in the tropical Andes

This article presents a hydrometeorological dataset from a network of paired instrumented catchments, obtained by participatory monitoring through a partnership of academic and non-governmental institutions. The network consists of 28 headwater catchments (<20 km2) covering three major biomes in 9 locations of the tropical Andes. The data consist of precipitation event records at 0.254 mm resolution or finer, water level and streamflow time series at 5 min intervals, data aggregations at hourly and daily scale, a set of hydrological indices derived from the daily time series, and catchment physiographic descriptors. The catchment network is designed to characterise the impacts of land-use and watershed interventions on the catchment hydrological response, with each catchment representing a typical land use and land cover practice within its location. As such, it aims to support evidence-based decision making on land management, in particular evaluating the effectiveness of catchment interventions, for which hydrometeorological data scarcity is a major bottleneck. The data will also be useful for broader research on Andean ecosystems, and their hydrology and meteorology