Hydroclimatological Processes in the ”Central America Dry Corridor” PI: Hugo G. Hidalgo ([email protected]) General objective. • To provide a better understanding of the processes that generate climate in the Central America Dry Corridor (CADC) in order to improve forecasts based on variability and to validate climate change projections. Specific objectives. • To determine the characteristics of the climate in the CADC with respect to the different climates of the isthmus. • To identify the sources of climatological aridity and the drought precursors in the CADC. • To identify relationships between existing vegetation and land surface processes. • To model hydrometeorological processes of the CADC (using hydrological models). • To provide projections of the expected climate change impacts in the Central America region and evaluate characteristics in the CADC. • To compare the climate change projections with the vulnerabilities detected in social indexes. • To improve precipitation seasonal forecasts by: a) including other predictor fields, other than the sea surface temperature, such as soil moisture, and b) the inclusion of other predictands, other than the seasonal accumulations, such as the days with precipitation, the 20th or the 80th percentiles. Motivation. Even that Central America is located in a tropical region with low hydric stress in a large part of its territory; droughts are also frequent in another large fraction of the area. In particular, the subregion known as “Corredor Seco Centroamericano” (Figure 1) or “Central America Dry Corridor” (CADC) is a relatively dry zone in climatological terms, a byproduct of the commonly observed drought conditions. “The CADC is an imprecise geographic demarcation that extends as a zone with climatic characteristics of a dry tropical forest, with an accentuated and long dry season (“verano”), and where there is a latent risk of recurring droughts during the reduced rainy season (“invierno”) caused by a late arrival of the invierno, an extension of the Mid-‐Summer Drought, or a premature stopping of the invierno” (Peralta Rodríguez 2012). “The term Dry Corridor suggests a climatic phenomena, but it also has an ecological basis: it defines a group of ecosystems that combine in the ecoregion of the dry tropical forest of Central America, that begins in Chiapas, Mexico, and in a strip of land that contains the low lands of the Pacific slope and a large part of the premontane central region (0 to 800 m.a.s.l.) of Guatemala, El Salvador, Honduras, Nicaragua and part of Costa Rica (up to Guanacaste); in Honduras it also includes fragments that reach out to the Caribbean slope” (van der Zee Arias et al. 2012a). Social vulnerabilities are mentioned in many studies related to the CADC, as the impacts of droughts and floods usually threaten food security. It is common to observe widespread impacts to these extreme events due to vulnerabilities related to poverty and the dependency of feeding and economic livelihood on subsistence agriculture (Peralta Rodríguez et al. 2012; van der Zee Arias et al. 2012a; 2012b). From a total of 10.5 millions of people that live in the rural areas of the dry tropics (almost all in Nicaragua, Honduras, and Guatemala), close to 60% live in poverty conditions and depend of deteriorated livelihoods (van de Zee Arias 2012a). In Costa Rica, drought affects water supply for human consumption, agriculture, cattle rising and tourism (La Nación 2014; 2015). Background The process that makes the CADC so susceptible to drought is related to the sources and mechanisms of transport of humidity that govern the climate of the subregion. Van der Zee Arias et al. (2012) have mentioned that the process that makes this zone drier than the Caribbean slope, is the presence of a “rain shadow” that is produced when the trade winds reach the mountain ranges and discharge their humidity in the Caribbean slope. A recent study by Hidalgo et al. (2015) suggests that this is an oversimplification of a complex climatic mechanism. The mechanism suggested by Hidalgo et al. (2015) implies the relationship of the Caribbean Low Level Jet (CLLJ; Amador 1998), convection produced near the isthmus and the southern displacement of the Intertropical Convergence Zone (ITCZ), especially during June-‐July-‐August. The role of the Northern Hemisphere Warm Pool in this process is still unknown (Hidalgo et al. 2015). A better understanding of these processes would help to improve seasonal forecasts, and also this research has implications related with the effects of climate change, and in particular with the climate projections from General Circulation Models (GCMs). For example, in Hidalgo et al. (2013) the runoff climate change projections at the end of the century were presented, using data from 30 GCM runs and a hydrological model. It was found that a southern displacement of the mean location of the ITCZ at the end of the century would bring drier conditions to Central America (on the order of 10% runoff reductions for southern Central America and 30% in the northern region). It is important to determine if: a) the connections found in Hidalgo et al. (2015) are validated in high-‐resolution hydrometeorological datasets, b) if the characteristics of the land surface (including vegetation) are key to increase the aridity, c) if there are connections between aridity with other processes such as the Mid-‐Summer Drought timing or the sowing timing, and d) if the GCMs show a realistic representation of the processes and connections suggested in Hidalgo et al. (2015), e) if there will be future changes in these connections, and g) if it is possible to validate the conclusions of Hidalgo et al. (2013) using higher resolution data (5 km grid resolution instead of 50 km). Referencias Amador, J.A., 1998. A climatic feature of the tropical Americas: the Trade Wind Easterly Jet. Tópicos Meteorológicos y Oceanográficos, 5, 91–102. Hidalgo, H.G., Durán-‐Quesada, A.M., Amador, J.A. and Alfaro, E.J., 2015. The Caribbean Low-‐Level Jet, the Inter-‐Tropical Convergence Zone and precipitation patterns in the Intra-‐Americas Sea: a proposed dynamical mechanism. Geografiska Annaler, Series A: Physical Geography. doi:10.1111/geoa.12085 Hidalgo, H.G., Amador, J.A., Alfaro, E.J., Quesada, B. 2013. Hydrological climate change projections for Central America. Journal of Hydrology 495: 94-‐112. La Nación. 2014. Guanacaste está sedienta. http://www.nacion.com/nacional/infraestructura/Guanacaste-‐
sedienta_0_1428657137.html La Nación. 2015. Hoteleros alistan medidas de emergencia por falta de aguahttp://www.nacion.com/economia/empresarial/Hoteleros-‐alistan-‐medidas-‐
emergencia-‐falta_0_1463253701.html Peralta Rodríguez, O., Carrazón Alocén, J., Zelaya Elvir, C. A. 2012. Buenas prácticas para la seguridad alimentaria y la gestión de riesgo. Publicado por: Organización de las Naciones Unidas para la Alimentación y la Agricultura (FAO). Pp. 53. van der Zee Arias, A., van der Zee, J., Meyrat, A., Poveda, C., Picado, L. 2012a. Estudio de la caracterización del Corredor Seco Centroamericano. Publicado por: Organización de las Naciones Unidas para la Alimentación y la Agricultura (FAO). Pp. 92. van der Zee Arias, A., van der Zee, J., Meyrat, A., Poveda, C., Picado, L. 2012b. Identificación de actores relevantes y relaciones interinstitucionales en el Corredor Seco Centroamericano. Publicado por: Organización de las Naciones Unidas para la Alimentación y la Agricultura (FAO). Pp. 122. Figure 1. Location of the Central America Dry Corridor (yellow area). Source: http://www.arcgis.com/apps/SocialMedia/index.html?appid=1f5588691fb34c8a8d1
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