The location of Costa Rica on the Central American Isthmus creates unique microclimate systems that receive moisture inputs directly from the Caribbean Sea and the Pacific Ocean. In Costa Rica, stable isotope monitori...The location of Costa Rica on the Central American Isthmus creates unique microclimate systems that receive moisture inputs directly from the Caribbean Sea and the Pacific Ocean. In Costa Rica, stable isotope monitoring was conducted by the International Atomic Energy Agency and the World Meteorological Association as part of the worldwide effort entitled Global Network of Isotopes in Precipitation. Sampling campaigns were mainly comprised of monthly-integrated samples during intermittent years from 1990 to 2005. The main goal of this study was to determine spatial and temporal isotopic variations of meteoric waters in Costa Rica using historic records. Samples were grouped in four main regions: Nicoya Peninsula (d2H = 6.65d18O -0.13;r2 = 0.86);Pacific Coast (d2H = 7.60d18O + 7.95;r2 = 0.99);Caribbean Slope (d2H = 6.97d18O + 4.97;r2 = 0.97);and Central Valley (d2H = 7.94d18O + 10.38;r2 = 0.98). The water meteoric line for Costa Rica can be defined as d2H = 7.61d18O + 7.40 (r2 = 0.98). The regression of precipitation amount and annual arithmetic means yields a slope of ﹣1.6‰ d18O per 100 mm of rain (r2 = 0.57) which corresponds with a temperature effect of ﹣0.37‰ d18O/°C. A strong correlation (r2 = 0.77) of ﹣2.0‰ d18O per km of elevation was found. Samples within the Nicoya Peninsula and Caribbean lowlands appear to be dominated by evaporation enrichment as shown in d-excess interpolation, especially during the dry months, likely resulting from small precipitation amounts. In the inter-mountainous region of the Central Valley and Pacific slope, complex moisture recycling processes may dominate isotopic variations. Generally, isotopic values tend to be more depleted as the rainy season progresses over the year. Air parcel back trajectories indicate that enriched isotopic compositions both in Turrialba and Monteverde are related to central Caribbean parental moisture and low rainfall intensities. Depleted events appear to be related to high rainfall amounts despite the parental origin of the moisture.展开更多
Little information is available for Central America regarding methane and carbon dioxide mixing ratios in urban areas. This work reports a representative spatial and seasonal study of near surface carbon dioxide and m...Little information is available for Central America regarding methane and carbon dioxide mixing ratios in urban areas. This work reports a representative spatial and seasonal study of near surface carbon dioxide and methane, carried out between July 2014 and January 2015 (27 weeks) in the Central Valley of Costa Rica, and other urban and rural sites across the country and covering three distinct seasons: Mid-summer drought (July-August), wet season (September-November) and transition period (December-January). The mixing ratios of both gases are clearly influenced by the metropolitan area, and by the prevailing atmospheric conditions during the wet season months. Average carbon dioxide concentration (629 ± 80 ppm) and average methane concentration (2192 ± 110 ppb) were up to 8% and up to 10%, respectively, higher during the wet season than the values recorded outside this period. HYSPLIT back air mass trajectories analysis, and weather data available for the Central Valley, suggest that these differences arise as result of a reduction in the mixing layer of depth (~425 m) and the wind speed (~1.5 m/s) across the valley, favoring the accumulation of polluted air masses in the metropolitan area. Other natural and anthropogenic sources, like the volcanic emissions of the Turrialba Volcano and the livestock activities at rural sites, apparently influence the mixing ratios of both gases across Costa Rica. Although the scope of this study is limited to representative seasonal conditions of the Central Valley in 2014 and 2015, it is possible considering the information presented in this work that the “dome” phenomenon can be assumed to exist.展开更多
文摘The location of Costa Rica on the Central American Isthmus creates unique microclimate systems that receive moisture inputs directly from the Caribbean Sea and the Pacific Ocean. In Costa Rica, stable isotope monitoring was conducted by the International Atomic Energy Agency and the World Meteorological Association as part of the worldwide effort entitled Global Network of Isotopes in Precipitation. Sampling campaigns were mainly comprised of monthly-integrated samples during intermittent years from 1990 to 2005. The main goal of this study was to determine spatial and temporal isotopic variations of meteoric waters in Costa Rica using historic records. Samples were grouped in four main regions: Nicoya Peninsula (d2H = 6.65d18O -0.13;r2 = 0.86);Pacific Coast (d2H = 7.60d18O + 7.95;r2 = 0.99);Caribbean Slope (d2H = 6.97d18O + 4.97;r2 = 0.97);and Central Valley (d2H = 7.94d18O + 10.38;r2 = 0.98). The water meteoric line for Costa Rica can be defined as d2H = 7.61d18O + 7.40 (r2 = 0.98). The regression of precipitation amount and annual arithmetic means yields a slope of ﹣1.6‰ d18O per 100 mm of rain (r2 = 0.57) which corresponds with a temperature effect of ﹣0.37‰ d18O/°C. A strong correlation (r2 = 0.77) of ﹣2.0‰ d18O per km of elevation was found. Samples within the Nicoya Peninsula and Caribbean lowlands appear to be dominated by evaporation enrichment as shown in d-excess interpolation, especially during the dry months, likely resulting from small precipitation amounts. In the inter-mountainous region of the Central Valley and Pacific slope, complex moisture recycling processes may dominate isotopic variations. Generally, isotopic values tend to be more depleted as the rainy season progresses over the year. Air parcel back trajectories indicate that enriched isotopic compositions both in Turrialba and Monteverde are related to central Caribbean parental moisture and low rainfall intensities. Depleted events appear to be related to high rainfall amounts despite the parental origin of the moisture.
文摘Little information is available for Central America regarding methane and carbon dioxide mixing ratios in urban areas. This work reports a representative spatial and seasonal study of near surface carbon dioxide and methane, carried out between July 2014 and January 2015 (27 weeks) in the Central Valley of Costa Rica, and other urban and rural sites across the country and covering three distinct seasons: Mid-summer drought (July-August), wet season (September-November) and transition period (December-January). The mixing ratios of both gases are clearly influenced by the metropolitan area, and by the prevailing atmospheric conditions during the wet season months. Average carbon dioxide concentration (629 ± 80 ppm) and average methane concentration (2192 ± 110 ppb) were up to 8% and up to 10%, respectively, higher during the wet season than the values recorded outside this period. HYSPLIT back air mass trajectories analysis, and weather data available for the Central Valley, suggest that these differences arise as result of a reduction in the mixing layer of depth (~425 m) and the wind speed (~1.5 m/s) across the valley, favoring the accumulation of polluted air masses in the metropolitan area. Other natural and anthropogenic sources, like the volcanic emissions of the Turrialba Volcano and the livestock activities at rural sites, apparently influence the mixing ratios of both gases across Costa Rica. Although the scope of this study is limited to representative seasonal conditions of the Central Valley in 2014 and 2015, it is possible considering the information presented in this work that the “dome” phenomenon can be assumed to exist.
