Meso-scale effects of tropical deforestation in Amazonia: preparatory LBA modelling studies

Dolman, A.J.; Dias, M. A. Silva; Calvet, Jean‐Christophe; Ashby, Mark; Tahara, A. S.; Delire, Christine; Kabat, P.; Fisch, Gilberto; Nobre, Carlos A.

doi:10.1007/s00585-999-1095-0

Cited by 19 publications

(8 citation statements)

References 29 publications

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“…Still, both timing and depth of the CBL seems to have been significantly underestimated over pasture, when compared with observations made concurrently at the same sites , arguably due to the inability of one-dimensional models to reproduce the thermal instabilities induced across the surrounding deforested strips. Similar results were encountered by Dolman et al (1999), who noted that modeling CBL over pastures in Rondônia may not only make it seem lower than observations (Calvet et al, 1997) but also colder and wetter, indicating the failure of SCMs to generate the necessary amount of heat to induce a deeper and warmer CBL. These findings were supported by additional experiments performed by Dolman et al (1999), who showed that even mesoscale gridded models may fail to properly predict both depth and temperature of the CBL over pastures in Rondônia, despite their ability to simulate the Tennekes (1973).…”

Section: Single-column Models (Scms)supporting

confidence: 80%

“…Atmospheric instabilities induced between areas of forest and pasture (Dolman et al, 1999;Liu et al, 1999;Baidya Roy and Avissar, 2000;Souza et al, 2000;Weaver and Avissar, 2001) are thus better represented by mesoscale models, which have showed that the impact of such instabilities are (typically) quite different from the results encountered by AGCM simulations of a basin-wide deforestation (Table II).…”

Section: Mesoscale Modelsmentioning

confidence: 99%

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The effects of deforestation on the hydrological cycle in Amazonia: a review on scale and resolution

D’Almeida

Vörösmarty

Hurtt

et al. 2007

Intl Journal of Climatology

227

137

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Abstract:This paper reviews the effects of deforestation on the hydrological cycle in Amazonia according to recent modeling and observational studies performed within different spatial scales and resolutions. The predictions that follow from future scenarios of a complete deforestation in the region point to a restrained water cycle, while the simulated effects of small, disturbed areas show a contrasting tendency. Differences between coarsely spatially averaged observations and finely sampled data sets have also been encountered. These contrasts are only partially explained by the different spatial resolutions among models and observations, since they seem to be further associated with the weakening of precipitation recycling under scenarios of extensive deforestation and with the potential intensification of convection over areas of land-surface heterogeneity. Therefore, intrinsic and interrelated scale and heterogeneity dependencies on the impact of deforestation in Amazonia on the hydrological cycle are revealed and the acknowledgement of the relevance of these dependencies sets a few challenges for the future.

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Section: Single-column Models (Scms)supporting

confidence: 80%

Section: Mesoscale Modelsmentioning

confidence: 99%

The effects of deforestation on the hydrological cycle in Amazonia: a review on scale and resolution

D’Almeida

Vörösmarty

Hurtt

et al. 2007

Intl Journal of Climatology

227

137

View full text Add to dashboard Cite

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“…In recent years, a variety of LBA results have been published. Available data range from those related to the mesoscale effects of tropical deforestation [ Dolman et al , 1999] to those describing biosphere‐atmosphere interactions, interactions among cloud and rain processes [ Silva Dias et al , 2002a], aerosol‐cloud interactions [ Andreae et al , 2004] and the transport of biomass burning emissions [ Freitas et al , 2006]. Specific data used in the numerical simulations were CCN concentrations and shape parameters of gamma functions representing cloud droplet spectra, as described by Martins et al [2004] and Gonçalves et al [2008].…”

Section: Introductionmentioning

confidence: 99%

Impact of biomass burning aerosols on precipitation in the Amazon: A modeling case study

Martins¹,

Dias²,

Gonçalves³

2009

J. Geophys. Res.

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[1] A study of the potential role of aerosols in modifying clouds and precipitation is presented using a numerical atmospheric model. Measurements of cloud condensation nuclei (CCN) and cloud size distribution properties taken in the southwestern Amazon region during the transition from dry to wet seasons were used as guidelines to define the microphysical parameters for the simulations. Numerical simulations were carried out using the Brazilian Development on Regional Atmospheric Modeling System, and the results presented considerable sensitivity to changes in these parameters. High CCN concentrations, typical of polluted days, were found to result in increases or decreases in total precipitation, depending on the level of pollution used as a reference, showing a complexity that parallels the aerosol-precipitation interaction. Our results show that on the grids evaluated, higher CCN concentrations reduced low-to-moderate rainfall rates and increased high rainfall rates. The principal consequence of the increased pollution was a change from a warm to a cold rain process, which affected the maximum and overall mean accumulated precipitation. Under polluted conditions, cloud cover diminished, allowing greater amounts of solar radiation to reach the surface. Aerosol absorption of radiation in the lower layers of the atmosphere delayed convective evolution but produced higher maximum rainfall rates due to increased instability. In addition, the intensity of the surface sensible heat flux, as well as that of the latent heat flux, was reduced by the lower temperature difference between surface and air, producing greater energy stores at the surface.

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“…These studies focused on the exchange of heat, water vapor, CO 2 , and other trace gases between the primary forest and the atmosphere (e.g., Fitzjarrald et al , 1990; Fitzjarrald & Moore, 1990; Wofsy et al , 1990). Determining the consequences of Amazon deforestation has been the focus of many numerical model studies (Nobre et al , 1991; Lean & Rowntree, 1993; Dolman et al , 1999). Observational studies specifically aimed to determine the impact of deforestation on climate and carbon exchange in the Amazon include the ABRACOS project (Anglo‐Brazilian Amazonian Climate Observation Study; Shuttleworth et al , 1991; Fisch, 1996; Gash et al , 1996) and LBA (Large‐Scale Biosphere–Atmosphere Experiment in Amazonia) field experiments.…”

Section: Introductionmentioning

confidence: 99%

Land‐use change effects on local energy, water, and carbon balances in an Amazonian agricultural field

Sakai

Fitzjarrald

Moraes

et al. 2004

Global Change Biology

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To study how changing agricultural practices in the eastern Amazon affect carbon, heat and water exchanges, a 20 m tower was installed in a field in August 2000. Measurements include turbulent fluxes (momentum, heat, water vapor, and CO 2 ) using the eddy covariance (EC) approach, soil heat flux, wind, and scalar profiles (T, q, and CO 2 ), soil moisture content, terrestrial, total solar radiation, and photosynthetically active radiation (PAR, 400-700 nm). At the beginning of the measurements, in September 2000, the field was a pasture. On November 2001, the pasture was burned, plowed, and planted in upland (nonirrigated) rice.Calm nights were the norm in this site. Anomalously low values of net ecosystem exchange (NEE) were found using the EC method, even when the common criterion u Ã o0.2 m s À1 was used to identify and exclude poor performance nights. We observed more plausible values of NEE using criterion u Ã o0.08 m s À1 , indicating that the criterion must be revised downward for flow over surfaces smoother than forests. However, even using the lower threshold, u Ã was lower than this limit for 82% of nights, and this led to nocturnal respiration underestimates. We compensate for this difficulty by estimating the respiration rate using the nocturnal boundary layer budget method.Land-use change from pasture to rice cultivation strongly affected both diurnal rates of turbulent exchange but also the pattern of seasonal variation. Seasonal wet and dry season differences in vegetation state were clearly detected in the albedo and PARalbedo. These reflectivity changes were accompanied by modified net radiative flux, turbulent heat flux and evaporation rates. The highest evaporation rate was observed during the rice crop, when the field had total evaporation approximately half the precipitation input, less than that of the surrounding forest. Effects of the land-cover changes were also detected in the carbon budget. For the pasture, the maximum CO 2 uptake occurred in May, appreciably delayed from the start of the rainy season. After the field was plowed and the soil was exposed and there was efflux of CO 2 to the atmosphere day and night for an extended period. Highest values of carbon uptake occurred during the rice plantation. Although the upland rice took up carbon at double the rate of the pasture that it replaced, the field was left fallow for much of the year, during the dry season.

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Meso-scale effects of tropical deforestation in Amazonia: preparatory LBA modelling studies

Cited by 19 publications

References 29 publications

The effects of deforestation on the hydrological cycle in Amazonia: a review on scale and resolution

The effects of deforestation on the hydrological cycle in Amazonia: a review on scale and resolution

Impact of biomass burning aerosols on precipitation in the Amazon: A modeling case study

Land‐use change effects on local energy, water, and carbon balances in an Amazonian agricultural field

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