Papers by Antonio Donato Nobre
Frontiers in forests and global change, Jul 20, 2023
arXiv (Cornell University), Jun 23, 2021
While water lifting plays a recognized role in the global atmospheric power budget, estimates for... more While water lifting plays a recognized role in the global atmospheric power budget, estimates for this role in tropical cyclones vary from no effect to a major reduction in storm intensity. To better assess this impact, here we consider the work output of an infinitely narrow thermodynamic cycle with two streamlines connecting the top of the boundary layer in the vicinity of maximum wind (without assuming gradient-wind balance) to an arbitrary level in the inviscid free troposphere. The reduction of a storm's maximum wind speed due to water lifting is found to decline with increasing efficiency of the cycle and is about 5% for maximum observed Carnot efficiencies. In the steady-state cycle, there is an extra heat input associated with the warming of precipitating water. The corresponding positive extra work is of an opposite sign and several times smaller than that due to water lifting. We also estimate the gain of kinetic energy in the outflow region. Contrary to previous assessments, this term is found to be large when the outflow radius is small (comparable to the radius of maximum wind). Using our framework, we show that Emanuel's maximum potential intensity (E-PI) corresponds to a cycle where total work equals work performed at the top of the boundary layer (net work in the free troposphere is zero). This constrains a dependence between the outflow temperature and heat input at the point of maximum wind, but does not constrain the radial pressure gradient. We outline the implications of the established patterns for assessing real storms.
arXiv (Cornell University), May 11, 2015
The pattern and size of the Earth's atmospheric circulation cells determine regional climates and... more The pattern and size of the Earth's atmospheric circulation cells determine regional climates and challenge theorists. Here the authors present a theoretical framework that relates the size of meridional cells to the kinetic energy generation within them. Circulation cells are considered as heat engines (or heat pumps) driven by surface gradients of pressure and temperature. This approach allows an analytical assessment of kinetic energy generation in the meridional cells from the known values of surface pressure and temperature differences across the cell, Δp s and ΔT s. Two major patterns emerge. First, the authors find that kinetic energy generation in the upper and lower atmosphere respond in contrasting ways to surface temperature: with growing ΔT s , kinetic energy generation increases in the upper atmosphere but declines in the lower. A requirement that kinetic energy generation must be positive in the lower atmosphere can limit the poleward cell extension of the Hadley cells via a relationship between Δp s and ΔT s. The limited extent of the Hadley cells necessitates the appearance of heat pumps (Ferrel cells)circulation cells with negative work output. These cells consume the positive work output of the Hadley cells (heat engines) and can in theory drive the global efficiency of an axisymmetric atmospheric circulation down to zero. Second, the authors show that, within a cell, kinetic energy generation is largely determined by ΔT s in the upper atmosphere, and by Δp s in the lower. By absolute magnitude, the temperature contribution is about 10 times larger. However, since the heat pumps act as sinks of kinetic energy in the upper atmosphere, the net kinetic energy generation in the upper atmosphere, as well as the net impact of surface temperature, is reduced. The authors use NCAR/NCEP and MERRA data to verify the obtained theoretical relationships. These observations confirm considerable cancellation between the temperature-related sources and sinks of kinetic energy in the upper atmosphere. Both the theoretical approach and observations highlight a major contribution from surface pressure gradients, rather than temperature, in the kinetic energy budget of meridional circulation. The findings urge increased attention to surface pressure gradients as determinants of the meridional circulation patterns.
The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence
Global Change Biology
The terrestrial water cycle links the soil and atmosphere moisture reservoirs through four fluxes... more The terrestrial water cycle links the soil and atmosphere moisture reservoirs through four fluxes: precipitation, evaporation, runoff, and atmospheric moisture convergence (net import of water vapor to balance runoff). Each of these processes is essential for sustaining human and ecosystem well‐being. Predicting how the water cycle responds to changes in vegetation cover remains a challenge. Recently, changes in plant transpiration across the Amazon basin were shown to be associated disproportionately with changes in rainfall, suggesting that even small declines in transpiration (e.g., from deforestation) would lead to much larger declines in rainfall. Here, constraining these findings by the law of mass conservation, we show that in a sufficiently wet atmosphere, forest transpiration can control atmospheric moisture convergence such that increased transpiration enhances atmospheric moisture import and results in water yield. Conversely, in a sufficiently dry atmosphere increased tr...
Patterns of 'CO IND. 2' and water fluxes measured by flux towers across tropical forest, ecotone and savanna ecosystems in Brazil
Proceedings of the 1st iLEAPS sciences Conference, 2006
Data for: Development of an automated and open source GIS tool for reproducing the HAND terrain model
The HAND tool was developed using Python programming language which uses functionalities of a com... more The HAND tool was developed using Python programming language which uses functionalities of a commercial geographic information system for constructing the HAND model and terrain map. This tool can be used in ArcGIS 10.2.
The other side of drought: What is the effect of hydrological environment on Amazon forest "green-up" and drought responses?
Falhas e retrocessos da legislação ambiental. [Depoimento a Sylvia Miguel]
LBA-ECO CD-32 Flux Tower Network Data Compilation, Brazilian Amazon: 1999-2006
This data set is a compilation of carbon and energy eddy covariance flux, meteorology, radiation,... more This data set is a compilation of carbon and energy eddy covariance flux, meteorology, radiation, canopy temperature, humidity, and CO2 profiles and soil moisture and temperature profile data that were collected at nine towers across the Brazilian Amazon. Independent investigators provided the data from a variety of flux tower projects over the period 1999 thru 2006. The data have been harmonized across projects, additional quality control checks were performed, and the data were aggregated to several time intervals. Two versions of data are provided. One version is as received from the investigators and the second was processed through a series of automated and manual quality control steps. This data set includes 18 compressed (*.zip) data files with the two versions of data files for each of the nine sites.
Boundary-Layer Meteorology, 2000
The turbulence structure in two Amazon rain forests was characterised for a range of above-canopy... more The turbulence structure in two Amazon rain forests was characterised for a range of above-canopy stability conditions, and the results compared with previous studies in other forest canopies and recent theory for the generation of turbulent eddies just above forest canopies. Threedimensional wind speed and temperature fluctuation data were collected simultaneously at up to five levels inside and above two canopies of 30-40 m tall forests, during three separate periods. We analysed hourly statistics, joint probability distributions, length scales, spatial correlations and coherence, as well as power spectra of vertical and horizontal wind speed. The daytime results show a sharp attenuation of turbulence in the top third of the canopies, resulting in very little movement, and almost Gaussian probability distributions of wind speeds, in the lower canopy. This contrasts with strongly skewed and kurtotic distributions in the upper canopy. At night, attenuation was even stronger and skewness vanished even in the upper canopy. Power spectral peaks in the lower canopy are shifted to lower frequencies relative to the upper canopy, and spatial correlations and coherences were low throughout the canopy. Integral length scales of vertical wind speed at the top of the canopy were small, about 0.15 h compared to a value of 0.28 h expected from the shear length scale at the canopy top, based on the hypothesis that the upper canopy air behaves as a plane mixing layer. All this suggests that, although exchange is not totally inhibited, tropical rain forest canopies differ from other forests in that rapid, coherent downward sweeps do not penetrate into the lower canopy, and that length scales are suppressed. This is associated with a persistent inversion of stability in that region compared to above-canopy conditions. The inversion is likely to be maintained by strong heat absorption in the leaves concentrated near the canopy top, with the generally weak turbulence being unable to destroy the temperature gradients over the large canopy depth.
Lba-Eco CD-08 Coarse Wood Litter Respiration and Decomposition, Manaus, Brazil
ORNL Distributed Active Archive Center Datasets
Environmental Modelling & Software, 2018
Height Above the Nearest Drainage (HAND), a state-of-the-art topo-hydrological index, has been in... more Height Above the Nearest Drainage (HAND), a state-of-the-art topo-hydrological index, has been increasingly used in geo-environmental studies. It describes the local normalized drainage potential of a large region. To date, a trial and error and cumbersome multistep process has been used to obtain the HAND index which does not result in an optimal threshold for contributing area. This study aims at developing a user-friendly geographic information system (GIS) tool, HANDTool, using the Python programming language. We successfully applied the tool for the Chehel-Chai watershed, Iran and the random forest algorithm was used to model groundwater potential. Results revealed that the HAND index made a great contribution to groundwater potential modeling among the other conditioning factors. This tool gives valuable insights on the soil-topography-moisture shared interactions and vegetation condition, especially in ungauged watersheds.
Biogeosciences, Sep 14, 2007
We obtained regional estimates of surface CO 2 exchange rates using atmospheric boundary layer bu... more We obtained regional estimates of surface CO 2 exchange rates using atmospheric boundary layer budgeting techniques above tropical forest near Manaus, Brazil. Comparisons were made with simultaneous measurements from two eddy covariance towers below. Although there was good agreement for daytime measurements, large differences emerged for integrating periods dominated by the night-time fluxes. These results suggest that a systematic underestimation of night time respiratory effluxes may be responsible for the high Amazonian carbon sink suggested by several previous eddy covariance studies. Large CO 2 fluxes from riverine sources or high respiratory losses from recently disturbed forests do not need to be invoked in order to balance the carbon budget of the Amazon. Our results do not, however, discount some contribution of these processes to the overall Amazon carbon budget.
NOCTURNAL ACCUMULATION OF CO<sub>2</sub>UNDERNEATH A TROPICAL FOREST CANOPY ALONG A TOPOGRAPHICAL GRADIENT
Ecological Applications, Sep 1, 2008
Flux measurements of carbon dioxide and water vapor above tropical rain forests are often difficu... more Flux measurements of carbon dioxide and water vapor above tropical rain forests are often difficult to interpret because the terrain is usually complex. This complexity induces heterogeneity in the surface but also affects lateral movement of carbon dioxide (CO2) not readily detected by the eddy covariance systems. This study describes such variability using measurements of CO2 along vertical profiles and along a toposequence in a tropical rain forest near Manaus, Brazil.Seasonal and diurnal variation was recorded, with atmospheric CO2 concentration maxima around dawn, generally higher CO2 build‐up in the dry season and stronger daytime CO2 drawdown in the wet season. This variation was reflected all along the toposequence, but the slope and valley bottom accumulated clearly more CO2 than the plateaus, depending on atmospheric stability. Particularly during stable nights, accumulation was along lines of equal altitude, suggesting that large amounts of CO2 are stored in the valleys of the landscape. Flushing of this store only occurs during mid‐morning, when stored CO2 may well be partly transported back to the plateaus. It is clear that, for proper interpretation of tower fluxes in such complex and actively respiring terrain, the horizontal variability of storage needs to be taken into account not only during the night but also during the mornings.
Disinformation permeates Castro's reply to Rajão et al. (2022)
Biological Conservation
arXiv (Cornell University), Jan 24, 2023
Along with the accumulation of atmospheric carbon dioxide, the loss of primary forests and other ... more Along with the accumulation of atmospheric carbon dioxide, the loss of primary forests and other natural ecosystems is a major disruption of the Earth system causing global concern. Quantifying planetary warming from carbon emissions, global climate models highlight natural forests' high carbon storage potential supporting conservation policies. However, some model outcomes effectively deprioritize conservation of boreal and temperate forests suggesting that increased albedo upon deforestation could cool the planet. Potential conflict of global cooling versus regional forest conservation could harm environmental policies. Here we present theoretical and observational evidence to demonstrate that, compared to the carbon-related warming, the model skills for assessing climatic impacts of deforestation is low. We argue that deforestation-induced global cooling results from the models' limited capacity to account for the global effect of cooling from evapotranspiration of intact forests. Transpiration of trees can change the greenhouse effect via small modifications of the vertical temperature profile. Due to their convective parameterization (which postulates a certain critical temperature profile), global climate models do not properly capture this effect. This parameterization may lead to underestimation of warming from the loss of evapotranspiration in both high and low latitidues, and therefore, conclusions about deforestation-induced global cooling are not robust. To avoid deepening the environmental crisis, these conclusions should not inform policies of vegetation cover management. Studies are mounting quantifying the stabilizing impact of natural ecosystems evolved to maintain environmental homeostasis. Given the critical state and our limited understanding of both climate and ecosystems, an optimal policy would be a global moratorium on the exploitation of all natural forests.
Regional ecotypes structure biogeography of Amazon forest drought resilience and vulnerability
&lt;p&gt;Amazonia contains the most extensive tropical forests on Earth, but the role of ... more &lt;p&gt;Amazonia contains the most extensive tropical forests on Earth, but the role of the region as a carbon appears to be declining. Increasing deforestation, fire and climate change-associated increases in drought, threaten to push forests past a tipping point. However, forests are complex, exhibiting drought responses indicative of both resilience (photosynthetic &amp;#8220;greening&amp;#8221;) and vulnerability (browning and tree mortality) that are difficult to explain by climate variation alone. Still needed is a framework for understanding and predicting how different regions will respond to different kinds of future drought. Here, we combine remotely-sensed photosynthetic vegetation indices (enhanced vegetation index, EVI, corrected for sun-sensor geometry; and solar-induced chlorophyll fluorescence, SIF) with ground-based tree demography to test recent ecological hypotheses about forest drought resilience and vulnerability for different forest ecotypes across the basin, defined by their water-table depth, soil fertility and vegetation characteristics. In high-fertility southern Amazonia, drought response was importantly structured by water-table depth, with resilient greening in shallow-water-table-forests (where greater water availability heightened responsiveness to excess sunlight) contrasting with vulnerability (&amp;#8220;browning&amp;#8221; and excess tree mortality) over deeper water tables. Notably, shallow-water-table-forest resilience weakened as droughts lengthened. By contrast, low-fertility northern Amazonia, with slower-growing but drought-hardy trees (or tall trees, with deep-rooted water access), supported more drought-resilient forests independent of water-table depth. This work reveals a new biogeography of forest drought response that provides a framework for conservation decisions and improved prediction of heterogeneous forest responses to future climate changes, but warns that longer/more frequent droughts undermine these multiple ecohydrological strategies of Amazon forest resilience.&lt;/p&gt;
Communications Earth & Environment
Careful management of deforested Amazonian land cannot replace, but must complement, efforts to p... more Careful management of deforested Amazonian land cannot replace, but must complement, efforts to preserve the rainforest. Sustainable agricultural practices that promote diverse uses can help minimise climate and environmental impacts. Different land uses in deforested regions of Amazonia can have very different impacts on the climate and environment. Although different sectors of society are engaged in efforts to curb Amazonian deforestation, the consequences of land use in deforested areas have not received enough attention. After deforestation, the remaining forest fragments continue to be affected by ecosystem disturbances in the surrounding areas. These disturbances have profound effects not only on the biodiversity and functioning of remaining forests but also on agribusiness. We argue that we need a land-use revolution toward the management of deforested lands that takes an environmental, social and economic perspective. Rapidly changing land use The uses of deforested areas in the Amazon region are under constant change. After the 1970s, a combination of technological advances, including plant breeding and soil acidity correction (i.e., liming), led to the expansion of soybean plantations into Brazil's Savannas-the Cerrado-and the Southern Amazon frontier. Together, these advances marked a turning point for agricultural production in the Southern Amazon. Higher productivity and increasing profits created fertile ground for corporate farming and led to a rapid expansion of extensive monocultures 1. From 2000 to 2019, the area of soybean cultivation in the Amazon region increased more than 10-fold (Fig. 1), from 0.4 to 4.6 Mha 2. Not all deforestation is the same Environmental changes within remaining forest fragments often mirror changes in their surroundings 3. The climatic impacts that arise from forest loss depend on the size of deforested patches, on land use, and on the land management in those areas. Small-scale deforestation of patches below 10 km 2 in size leads to more shallow clouds as there is more convective energy in the system, and promotes higher volumes of rainfall 4. However, as deforested areas increase in size, convective lifting mechanisms lose force, which reduces the appearance of shallow clouds, and thereby evapotranspiration and rainfall 5. This shift is already taking place in many areas of Amazon 6 .
SN Applied Sciences
An improved version of the Integrated Land Surface Model (INLAND), incorporating the physical, ec... more An improved version of the Integrated Land Surface Model (INLAND), incorporating the physical, ecological and hydrological parameters and processes pertaining to two subclasses of tropical forest in the central Amazon basin, a poorly drained flat plateau and a well-drained adjacent broad valley, is used to simulate the hydrological, energy and CO2 fluxes. The model is forced with observed meteorological data. The experimental output data from the model runs are compared with observational data at the two locations. The seasonal variabilities of water table depth at the valley site and the soil moisture at the plateau site are satisfactorily simulated. The two locations exhibit large differences in energy, carbon and water fluxes, both in the simulations and in the observations. Results validate the INLAND model and indicate the need for incorporating sub-grid scale variability in the relief, soil type and vegetation type attributes to improve the representation of the Amazonian ecos...
SSRN Electronic Journal, 2022
Destabilization of the water cycle threatens human lives and livelihoods. Meanwhile our understan... more Destabilization of the water cycle threatens human lives and livelihoods. Meanwhile our understanding of whether and how changes in vegetation cover could trigger abrupt transitions in moisture regimes remains incomplete. This challenge calls for better evidence as well as for the theoretical concepts to describe it. Here we briefly summarise the theoretical questions surrounding the role of vegetation cover in the dynamics of a moist atmosphere. We discuss the previously unrecognized sensitivity of local wind power to condensation rate as revealed by our analysis of the continuity equation for a gas mixture. Using the framework of condensation-induced atmospheric dynamics, we then show that with the temperature contrast between land and ocean increasing up to a critical threshold, ocean-to-land moisture transport reaches a tipping point where it can stop or even reverse. Land-ocean temperature contrasts are affected by both global and regional processes, in particular, by the surface fluxes of sensible and latent heat that are strongly influenced by vegetation. Our results clarify how a disturbance of natural vegetation cover, e.g., by deforestation, can disrupt large-scale atmospheric circulation and moisture transport. In view of the increasing pressure on natural ecosystems, successful strategies of mitigating climate change require taking into account the impact of vegetation on moist atmospheric dynamics. Our analysis provides a theoretical framework to assess this impact. The available data for Eurasia indicate that the observed climatological land-ocean temperature contrasts are close to the threshold. This can explain the increasing fluctuations in the continental water cycle including droughts and floods and signifies a yet greater potential importance for large-scale forest conservation.
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Papers by Antonio Donato Nobre