Amazonia's Hydrologic Cycle and the Role of Atmospheric Recycling in Assessing Deforestation Effects

Lettau, H.; Lettau, Katharina; Molion, Luiz Carlos Baldicero

doi:10.1175/1520-0493(1979)107<0227:ahcatr>2.0.co;2

Cited by 145 publications

(90 citation statements)

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“…As was shown by Mintz (1984), the UCLA GCM produces almost no land precipitation in the dry soil case except for the Sahel, while the GLAS GCM produced considerable precipitation in the Amazon regions, the Sahel and southeast Asia. Studies for the hydrological cycle of the Amazon by Lettau et al (1979) and Salati (1987) stress the importance of the local recycling of water there.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The realization that deforestation has become an ecological crisis has led to extensive efforts to monitor the actual condition of the tropical rain forest and its decline (U.S. Government, 1980;Woodwell et al, 1987) and to investigate its possible effects on the biosphere and climate (Bolin, 1977;Gentry andLopez-Parodi, 1980, 1982;Woodwell et at, 1978Woodwell et at, , 1983Potter et al, 1975;Lettau et al, 1979;Dickinson, 1987).…”

Section: Introductionmentioning

confidence: 99%

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Influence of Soil Moisture and Surface Albedo Changes over the African Tropical Rain Forest on Summer Climate

Yamazaki¹,

Tokioka²

1988

Journal of the Meteorological Society of Japan

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Section: Summary and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of Soil Moisture and Surface Albedo Changes over the African Tropical Rain Forest on Summer Climate

Yamazaki¹,

Tokioka²

1988

Journal of the Meteorological Society of Japan

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“…Continuous recycling of water along the trajectory thus adds more and more water vapor to the airstream traveling westward, which carries an isotopic "memory" of the local amount effect. Because recycling may contribute to more than half of the precipitation in the western part of the basin (estimates vary between 50% and 88%) (46,47), isotopic signatures in these parts of the Amazon are therefore also expected to be partly a reflection of the accumulated local amount effects. We expect that these two mechanisms will enhance the differences in the isotopic signal between dry and wet years along the water-vapor trajectory, and thus exacerbate difference in isotopic signal in the western and eastern part of the basin.…”

Section: Possible Mechanisms Underlying the Strong Precipitation Signmentioning

confidence: 99%

Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Niño-Southern Oscillation variability

Brienen

Helle

Pons

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

170

142

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We present a unique proxy for the reconstruction of variation in precipitation over the Amazon: oxygen isotope ratios in annual rings in tropical cedar (Cedrela odorata). A century-long record from northern Bolivia shows that tree rings preserve the signal of oxygen isotopes in precipitation during the wet season, with weaker influences of temperature and vapor pressure. Tree ring δ 18 O correlates strongly with δ 18 O in precipitation from distant stations in the center and west of the basin, and with Andean ice core δ 18 O showing that the signal is coherent over large areas. The signal correlates most strongly with basin-wide precipitation and Amazon river discharge. We attribute the strength of this (negative) correlation mainly to the cumulative rainout processes of oxygen isotopes (Rayleigh distillation) in air parcels during westward transport across the basin. We further find a clear signature of the El Niño-Southern Oscillation (ENSO) in the record, with strong ENSO influences over recent decades, but weaker influence from 1925 to 1975 indicating decadal scale variation in the controls on the hydrological cycle. The record exhibits a significant increase in δ 18 O over the 20th century consistent with increases in Andean δ 18 O ice core and lake records, which we tentatively attribute to increased water vapor transport into the basin. Taking these data together, our record reveals a fresh path to diagnose and improve our understanding of variation and trends of the hydrological cycle of the world's largest river catchment.climate change | dendrochronology | plant physiology T he Amazon basin is a major center of atmospheric convection and precipitation (1), and at the same time the world's largest drainage basin. The Amazon's river discharge accounts for ∼17% of the annual global discharge to the oceans (2); its hydrological cycle is tightly linked with the carbon cycle of the Amazon rainforest (3), which itself is one of the largest terrestrial biomass carbon pools. Changes in the hydrological cycle of the Amazon may therefore significantly affect atmospheric dynamics and global climate by changing atmospheric CO 2 concentration. Two particularly severe droughts occurred within the last decade (4), and long-term river records of the Amazon show a steady increase in discharge over the last century (5), indicating that the system may start to undergo some changes. It has been suggested that these changes are a result of anthropogenic warming, but they may also be part of longer-term, natural climatic variability. To clarify such a globally important issue, long-term, accurate records of the hydrological cycle of the Amazon basin are needed. However, meteorological data are only reliable for the last 50-60 y (6), and annually resolved long-term proxies for the hydrological cycle from within the Amazon basin itself are very scarce (7).A commonly used diagnostic for strength and functioning of the water cycle is the isotopic composition of precipitation. Although variation of oxygen isotope ratios in precip...

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“…The concept of precipitation recycling has been explored in many studies focusing on land surface-atmosphere interactions (e.g., Eltahir and Bras 1994;Kunstmann and Jung 2007;Lettau et al 1979;Szeto et al 2008). The so-called precipitation-recycling ratio is used to quantify the contribution of local evaporation to precipitation in the same region.…”

Section: Introductionmentioning

confidence: 99%

Impacts of boreal hydroelectric reservoirs on seasonal climate and precipitation recycling as simulated by the CRCM5: a case study of the La Grande River watershed, Canada

Irambona¹,

Music

Nadeau

et al. 2016

Theor Appl Climatol

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Located in northern Quebec, Canada, eight hydroelectric reservoirs of a 9782-km 2 maximal area cover 6.4% of the La Grande watershed. This study investigates the changes brought by the impoundment of these reservoirs on seasonal climate and precipitation recycling. Two 30-year climate simulations, corresponding to pre-and post-impoundment conditions, were used. They were generated with the fifthgeneration Canadian Regional Climate Model (CRCM5), fully coupled to a 1D lake model (FLake). Seasonal temperatures and annual energy budget were generally well reproduced by the model, except in spring when a cold bias, probably related to the overestimation of snow cover, was seen. The difference in 2-m temperature shows that reservoirs induce localized warming in winter (+0.7 ± 0.02°C) and cooling in the summer (−0.3 ± 0.02°C). The available energy at the surface increases throughout the year, mostly due to a decrease in surface albedo. Fall latent and sensible heat fluxes are enhanced due to additional energy storage and availability in summer and spring. The changes in precipitation and runoff are within the model internal variability. At the watershed scale, reservoirs induce an additional evaporation of only 5.9 mm year −1 (2%). We use Brubaker's precipitation recycling model to estimate how much of the precipitation is recycled within the watershed. In both simulations, the maximal precipitation recycling occurs in July (less than 6%), indicating weak land-atmosphere coupling. Reservoirs do not seem to affect this coupling, as precipitation recycling only decreased by 0.6% in July.

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Amazonia's Hydrologic Cycle and the Role of Atmospheric Recycling in Assessing Deforestation Effects

Cited by 145 publications

References 0 publications

Influence of Soil Moisture and Surface Albedo Changes over the African Tropical Rain Forest on Summer Climate

Influence of Soil Moisture and Surface Albedo Changes over the African Tropical Rain Forest on Summer Climate

Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Niño-Southern Oscillation variability

Impacts of boreal hydroelectric reservoirs on seasonal climate and precipitation recycling as simulated by the CRCM5: a case study of the La Grande River watershed, Canada

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