Year-to-Year Variations of the Stable Isotopes in Precipitation in February at Cuiabá, Located on the Northern Fringe of Pantanal, Brazil

Abstract

Large year-to-year variations of δ18O were found in the precipitation recorded in the International Atomic Energy Agency/Global Network of Isotopes in Precipitation (IAEA/GNIP) database for February at Cuiabá, located on the northern fringe of Pantanal, Brazil. Three depleted years (1963, 1978, and 1968) and three enriched years (1966, 1984, and 1983) were chosen to investigate this phenomenon and to correlate the amount of precipitation, the occurrences of storm precipitation, and the vapor flux field. In the depleted years, precipitation exceeding the long-term mean was observed at Cuiabá, while the southward vapor flux from the Amazon basin was less than the long-term mean. Since d-excesses in these years were large in general, fast evaporation must contribute to the greater precipitation observed in these depleted years. In contrast, such common features were not found in the vapor flux field in the enriched years. The occurrences of storm precipitation are important in 1966, while the amount effect is responsible for 1984. In 1983, enriched meteoric water is attributed to both the occurrences of storm precipitation and vapor flux field.

Controls over spatial and seasonal variations on isotopic composition of the precipitation along the central and eastern portion of Brazil

“…Inclinations of these lines are close to 8, indicating a low evaporation effect; the interception is about 12-13 for most stations, probably due to effects of vapour recirculation along the transportation of air masses. For the Cuiabá station, the interception is about 7, this value could be associated with the proximity of this station to the moisture source located in the Amazonian region, as observed by Matsuyama et al [29].…”

“…Evaluation of temporal variations in isotopic composition of precipitation collected at Cuiabá GNIP station, located in the Brazilian central zone, has revealed that during the active period of the SACZ, more depleted values observed in precipitation were associated with the precipitation amount and the occurrence of storm precipitation, while during the inactive period of the SACZ, a weakening of the vapour flux coming from the Amazon basin was observed [28,29].…”

Comparison of atmospheric hydrology over convective continental regions using water vapor isotope measurements from space

“…Precipitation rates have been found to influence isotopic composition during the monsoonal seasons, and are suggested as one cause of the amount effect [e.g., Matsuyama et al , 2005; Vuille et al , 2005]. Table 1 shows significant negative relationships between wet season δ D values and GPCP daily rainfall rates for all regions.…”

Estimating water balance components of tropical wetland lakes in the Pantanal dry season, Brazil

“…Such water balance tracer approaches typically involve the analysis of stable water isotopes (Gibson et al 1993). Isotopic analysis of water has proven to be one of the most important tools for investigating the water budget of water bodies (Matsuyama et al 2005) and is indispensable for water balance studies in fairly inaccessible areas (Turner and Townley 2006). Insight into lake hydrological processes can be gained even with only a small number of samples (Rozanski et al 2000).…”