【文章內(nèi)容簡(jiǎn)介】 ecember and in January with the amount difference of 170 mm, merely 1/3 of the former amount and only one month in time difference, which is possibly related to the fast moving of the ITCZ in sum mer. Correspondingly, theδ18O in reservoirs also shows the bimodal seasonality, in which the variations of theδ18O in precipitation and in surface runoff have similarity: their two maximums appear in January and July and two minimums in April and October, with the negative correlation of stable isotopic ratio with water budget。 additionally, in vapor, two maximums of theδ18O appears in January and August and two minimums of theδ18O does in April and November. The second extremums are later than that in precipitation and in runoff. Such a result shows that, to a certain degree, the stable isotopes in reservoirs and vapor are impacted not only by largescale climatic conditions, for example the solar radiation and atmospheric circulation, but also by the vapor origins.Figure 2 The monthly variations of the O in precipitation (a),vapor (b), surface runoff (c), surface dew (d) and surface evaporation (e), with the corresponding water budgets at Manaus, Brazil. The magnitude of surface evaporation is related to atmospheric humidity. Compared Figure 2(e) with 2(b), the evaporation is relatively small at two maximal specific humidity in April and in December, but relatively great at the minimal specific humidity in July. Unlike the behaviors of precipitation, specific humidity and condensation, evaporation shows the weak seasonality and indistinctive correlation with theδ18O in evaporation. Seasonal variations of the 18O and waterThe surface infiltration water, originated primarily from atmospheric precipitation, shows a very good consistency with precipitation . As a result, 18the monthly meanδ18O in infiltration water is positively correlated to that in precipitation, but negatively to infiltration water in accordance with the amount effect. Compared with precipitation, the infiltration water is isotopic ally enriched markedly due to evaporation action.The variation of supersurface soil water is influenced not only by infiltration water but also by mass exchange with root region water and surface evaporation action. Impacted by the storage regulation and peak attenuation actions of soil, the seasonality of supersurface soil water is weakened. Correspondingly, theδ18O in superurface reservoir displays unclear seasonality and unmarked correlation with supersurface water. However, the surface evaporation keeps isotopic consistency with supersurface reservoir because of drawing water from supersurface soil directly . Comparatively, the evaporated vapor is isotopic ally depleted. The rootregion water and the subsurface runoff have all weak seasonality with slightly later time phase than precipitation. Usually, in the rainy season, bigger aquiclude and stronger subsurface runoff corresponds to the higher water table。 and in the dry season, smaller aquiclude and weaker subsurface runoff to the lower water table. Correspondingly, δ18O in reservoirs shows that, in the rainy season, the heavy precipitation and the produced strong infiltration have the marked impact on δ18O in rootregion reservoir and in the decrease of theδ18Oin rootregion reservoir and subsurface run off is in apparent. Additionally, it can be found that theδ18Oin subsurface runoff is equal to that in rootregion water because the mass plement mainly es from rootregion water. Seasonal variations of the O and water budgets in canopy reservoir The canopy storage water mainly es from the precipitation interception by canopy, the replenishment from condensation is less. Therefore, the seasonal variation of theδ18O in canopy reservoir is consistent with that in precipitation. In accordance withδ18O in canopy reservoir is inthe amount effect, the versely proportional to the canopy storage water: in the rainy season, more canopy storage water corresponds toδ18O in reservoir, and in dry season, less canopy lowerδ18O in reservoir. Compared with precipitation, canopy reservoir is isotopically enriched due to evaporation action. Because vegetation transpiration process is considered not to generate isotopic fractionation, theδ18O variation in canopy transpiration keeps consistent with that in rootregion water that furnishes the most of the canopy transpiration. By paring ,the canopy transpiration varies with contrary to canopy evaporation. In the dry season, the water furnishing to canopy evaporation is less for lighter precipitation, but canopy transpiration is more due to drier atmosphere。 in the rainy season, the water furnishing to canopy evaporation is more for heavier precipitation, but canopy transpiration is less due to moister atmosphere.3 Comparison between CLM simulated and actual results Manaus is one of sampling stations attached to the global survey network set by the International Atomic Energy Agency (IAEA) in cooperation with the World Meteorological Organization (WMO). There have been 26year stable isotopic survey records from 1965 to 1990 (absent from 1993 to 1995) at Manaus (:// ). On the monthly timescale, there is the marked amount effect between the actualδ18O in precipitation and precipitation amount with the confidence level above ,and the simulated amount effect has good consistency with the actual that.The relationship betweenδD andδ18O in atmospheric precipitation is called as the meteoric water line (MWL). The actual global MWL by Craig is D = +. The slope item of stands for parativ