Isotopic Variations and Internal Storm Dynamics in the Amazon Basin
Rainwater samples taken every 10 min, protected from fractionation by a hydrocarbon layer and collected every 12 h, are subjected to isotopic analyses to obtain a time series of oxygen and deuterium values through successive rain events in the eastern and central Amazon basin. Satellite imagery is used to characterize the rain events, and rain rates from recording rain gauges are used to delineate changes in internal rain production within each storm.
Three clear isotopic signals are seen in the storm systems examined. These three responses consist of depletion of heavy isotopes by as much as −6.7% in a single storm, depletion followed by enrichment, and little change in the isotopic signal. Each of these changes in isotopic content of the rainwater can be related to the internal rain-rate production, evaporation/condensation processes together with the implied convective/stratiform circulations of the storm. The storm-related isotopic results suggest, in addition to illuminating the internal dynamics of these storm systems, that sampling of rain from any given rain-producing system can yield significantly different isotopic values. Conclusions about the large-scale hydrologic cycle and the sources and pathways followed by water contained within rain must take these internal storm variations in isotopic values into account.
Unable to display preview. Download preview PDF.
- Adar, E., and A. Long, 1987: Oxygen-18 and deuterium distribution in rainfall, runoff and groundwater in a small semi-arid basin: The Aravaipa Valley in the Sonora Desert, Arizona. IAEA Rep. SM-299/135, 15 pp.Google Scholar
- Faure, G., 1986: Principles of Isotope Geology. John Wiley and Sons, 589 pp.Google Scholar
- Garstang, M.,and D. R. Fitzjarrald, 1999: Observations of Surface to Atmosphere Interactions in the Tropics. Oxford University Press Inc., 405 pp.Google Scholar
- Gedzelman, S. D., and R. Arnold, 1994: Modeling the isotopic composition of precipitation. J. Geophys. Res., 99, 10 455–10 471.Google Scholar
- Greco, S., R. Swap, M. Garstang, S. Ulanski, M. Shipham, R. Harriss, R. Talbot, M. Andreae, and P. Artaxo, 1990: Rainfall and surface kinematic conditions over central Amazonia during ABLE 2B. J. Geophys. Res., 95, 17 001–17 014.Google Scholar
- Hoefs, J.,1987: Stable Isotope Geochemistry. Springer-Verlag, 241 pp.Google Scholar
- Houze, R. A., 1993: Cloud Dynamics. Academic Press, 573 pp.Google Scholar
- Miyake, Y., O. Matsubaya, and C. Nishihara, 1968: An isotopic study on meteoric precipitation. Pap. Meteorol. Geophys., 19, 243266.Google Scholar
- Schirmer, T., 1995: Die Zusammensetzung (D, 180 und ausgewählte Inhaltsstoffe) von Einzelniederschlagsereignissen Göttingens und Clausthal-Zellerfelds für den Zeitraum vom Mai 93 bis zum Marz 94. Diplomarbeit, University of Göttingen.Google Scholar
- Swap, R. J., August 1990: The nature and origin of central Amazonian wet season rainfall. M.S. thesis, Department of Environmental Sciences, University of Virginia, 116 pp.Google Scholar
- Victoria, R. L., L. A. Martinelli, J. Mortatti, and J. Richey, 1991: Mechanisms of water recycling in the Amazon Basin: Isotopic insights. Ambio, 20, 384–387.Google Scholar