Stable water isotope simulation in different reservoirs of Manaus, Brazil, by Community Land Model incorporating stable isotopic effect

Abstract The daily and monthly variations of stable water isotopes in different reservoirs at Manaus, Brazil, are simulated and inter‐compared in an equilibrium year, using the Community Land Model (CLM) involving the stable isotopic effects as a diagnostic tool for an in‐depth understanding of the hydrometeorological processes. On the daily scale, the δ 18 O in precipitation, vapour and surface runoff have clear seasonality, with marked negative correlations with the corresponding water amount. However, the δ 18 O in surface dew displays marked positive correlation with dew amount. On the diurnal time scale, the δ 18 O in precipitation displays an unclear diurnal variation and an unmarked correlation with the precipitation amount. However, the δ 18 O in vapour keeps consistency with specific humidity. On the monthly time scale, the δ 18 O in precipitation and surface runoff displays distinct bimodal seasonality, with two maxima in January and in July, and two minima in April and in October; Vapor displays a similar bimodal pattern, two maxima appear in January and August, and two minima in April and November. The amount effect simulated on the monthly time scale has consistency with the actual survey result at the Manaus station, from 1965 to 1990, set up by International Atomic Energy Agency (IAEA)/World Meteorological Organization (WMO). In addition, the slope (7.49) and the intercept (6.25) of the simulated meteoric water line (MWL) are all smaller than those of the actual mean MWL. However, compared with the annual MWL, the simulated MWL lies within the variation range of actual MWLs. Copyright © 2008 Royal Meteorological Society