We apply different methods for detection of extreme phenomena (EP) in air-turbulent time series measured in the nocturnal boundary layer above the Amazon forest. The methods used were: (a) a Morlet ...complex wavelet transform, which is often used in analysis of non-linear application processes. Through the use of the wavelet, it is possible to observe a phase singularity that involves a strong interaction between an extensive range of scales; (b) recurrence plot tests, which were used to identify a sudden change between different stable atmospheric states. (c) statistical analysis of early-warning signals, which verify simultaneous increases in the autocorrelation function and in the variance in the state variable; and (d) analysis of wind speed versus turbulent kinetic energy to identify different turbulent regimes in the stable boundary layer. We found it is adequate to use a threshold to classify the cases of strong turbulence regime, as a result of the occurrence of EP in the tropical atmosphere. All methods used corroborate and indicate synergy between events that culminate in what we classify as EP of the stable boundary layer above the tropical forest.
Prolonged drought stress combined with high leaf temperatures can induce programmed leaf senescence involving lipid peroxidation, and the loss of net carbon assimilation during early stages of tree ...mortality. Periodic droughts are known to induce widespread tree mortality in the Amazon rainforest, but little is known about the role of lipid peroxidation during drought-induced leaf senescence. In this study, we present observations of green leaf volatile (GLV) emissions during membrane peroxidation processes associated with the combined effects of high leaf temperatures and drought-induced leaf senescence from individual detached leaves and a rainforest ecosystem in the central Amazon. Temperature-dependent leaf emissions of volatile terpenoids were observed during the morning, and together with transpiration and net photosynthesis, showed a post-midday depression. This post-midday depression was associated with a stimulation of C₅ and C₆ GLV emissions, which continued to increase throughout the late afternoon in a temperature-independent fashion. During the 2010 drought in the Amazon Basin, which resulted in widespread tree mortality, green leaf volatile emissions (C₆ GLVs) were observed to build up within the forest canopy atmosphere, likely associated with high leaf temperatures and enhanced drought-induced leaf senescence processes. The results suggest that observations of GLVs in the tropical boundary layer could be used as a chemical sensor of reduced ecosystem productivity associated with drought stress.
BUILDING THE NEXT GENERATION OF CLIMATE MODELERS Frassoni, Ariane; Castilho, Dayana; Rixen, Michel ...
Bulletin of the American Meteorological Society,
11/2018, Letnik:
99, Številka:
11
Journal Article
ACRIDICON–CHUVA CAMPAIGN Wendisch, Manfred; Pöschl, Ulrich; Andreae, Meinrat O. ...
Bulletin of the American Meteorological Society,
10/2016, Letnik:
97, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Between 1 September and 4 October 2014, a combined airborne and ground-based measurement campaign was conducted to study tropical deep convective clouds over the Brazilian Amazon rain forest. The new ...German research aircraft, High Altitude and Long Range Research Aircraft (HALO), a modified Gulfstream G550, and extensive ground-based instrumentation were deployed in and near Manaus (State of Amazonas). The campaign was part of the German–Brazilian Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems–Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitation Measurement) (ACRIDICON–CHUVA) venture to quantify aerosol–cloud–precipitation interactions and their thermodynamic, dynamic, and radiative effects by in situ and remote sensing measurements over Amazonia. The ACRIDICON–CHUVA field observations were carried out in cooperation with the second intensive operating period of Green Ocean Amazon 2014/15 (GoAmazon2014/5). In this paper we focus on the airborne data measured on HALO, which was equipped with about 30 in situ and remote sensing instruments for meteorological, trace gas, aerosol, cloud, precipitation, and spectral solar radiation measurements. Fourteen research flights with a total duration of 96 flight hours were performed. Five scientific topics were pursued: 1) cloud vertical evolution and life cycle (cloud profiling), 2) cloud processing of aerosol particles and trace gases (inflow and outflow), 3) satellite and radar validation (cloud products), 4) vertical transport and mixing (tracer experiment), and 5) cloud formation over forested/deforested areas. Data were collected in near-pristine atmospheric conditions and in environments polluted by biomass burning and urban emissions. The paper presents a general introduction of the ACRIDICON–CHUVA campaign (motivation and addressed research topics) and of HALO with its extensive instrument package, as well as a presentation of a few selected measurement results acquired during the flights for some selected scientific topics.
The aim of this study is to investigate the low‐frequency characteristics of diurnal turbulent scalar spectra and cospectra near the Amazonian rain forest during the wet and dry seasons. This is ...because the available turbulent data are often nonstationary and there is no clear spectral gap to separate data into “mean” and “turbulent” parts. Daubechies‐8 orthogonal wavelet is used to scale project turbulent signals in order to provide scale variance and covariance estimations. Based on the characteristics of the scale dependence of the scalar fluxes, some classification criteria of this scale dependence are investigated. The total scalar covariance of each 4‐hour data run is partitioned in categories of scale covariance contributions. This permits the study of some statistical characteristics of the scalar turbulent fields in each one of these classes and, thus, to give an insight and a possible explanation of the origin of the variability of the scalar fields close to the Amazonian forest. The results have shown that a two‐category classification is the most appropriate to describe the kind of observed fluctuations: “turbulent” and “mesoscale” contributions. The largest contribution of the sensible heat, latent heat, and CO2 covariance contributions occurs in the “turbulent” length scales. Mesoscale eddy motions, however, can contribute up to 30% of the total covariances under weak wind conditions. Analysis of scale correlation coefficient r(Tvq) between virtual temperature (Tv) and humidity (q) signals shows that the scale patterns of Tv and q variability are not similar and r(Tvq) < 1 for all analyzed scales. Scale humidity skewness calculations are negative during the dry season and positive during the wet season. This suggests that different boundary layer moisture regimes occur during the dry and wet seasons.
We compared forecasts of the Center for Weather Prediction and Climate Studies (Centro de Previsão de Tempo e Estudos Clim´ticos—CPTEC) General Circulation Model (GCM) and the mesoscale Eta Model ...with observations undertaken at the Rondonia Coordinated Enhanced Observing Period (CEOP) reference site, Brazil, for the dry period between 1 July and 1 September 2001. The Rondonia site is located in the Jaru Biological Reserve Area in the state of Rondonia within the Amazon region. The site is forested and is one of the Reference Sites of the Large-Scale Biosphere-Atmosphere Experiment in the Amazon Basin (LBA) Continental-Scale Experiment (CSE). Time series and mean diurnal cycles of precipitation, near-surface temperature, latent and sensible heat fluxes, surface incoming shortwave and net radiation fluxes are shown for 24-h and 48-h forecasts. In the global model, the predicted incoming shortwave radiation and net radiation are similar to observed values; however, this is accompanied by large overestimate of deep clouds and precipitation. Partition of the available energy results in an overestimate of the sensible heat fluxes and an underestimate of the latent heat fluxes. The latent heat fluxes are large shortly after rain, but decay quickly. No clear improvement is noted in the 48-h forecasts compared with the 24-h forecasts. The Eta Model is a grid-point limited-area model. Its precipitation forecasts are similar to observations; however, the model overestimates the incoming shortwave radiation, resulting in excessive net radiation. The Eta sensible and latent heat fluxes are both overestimated, and 48-h forecasts produce small improvements over the 24-h forecasts. Near-surface temperatures are overestimated by both models. The global model requires a reduction in precipitation production, and both models require a reduction in incoming short-wave radiation at the surface.
Isoprene (Is) emissions by plants represent a loss of carbon and energy resources leading to the initial hypothesis that fast growing pioneer species in secondary tropical forests allocate carbon ...primarily to growth at the expense of isoprenoid defenses. In this study, we quantified leaf isoprene and methanol emissions from the abundant pantropical pioneer tree species Vismia guianensis and ambient isoprene concentrations above a diverse secondary forest in the central Amazon. As photosynthetically active radiation (PAR) was varied (0 to 3000â¯Âµmolâ¯m.sup.-2 â¯s.sup.-1) under standard leaf temperature (30⯰C), isoprene emissions from V. guianensis increased without saturation up to 80â¯nmolâ¯m.sup.-2 â¯s.sup.-1 . A nonlinear increase in isoprene emissions with respect to net photosynthesis (Pn) resulted in the fraction of Pn dedicated to isoprene emissions increasing with light intensity (up to 2â¯% of Pn). Emission responses to temperature under standard light conditions (PAR of 1000â¯Âµmolâ¯m.sup.-2 â¯s.sup.-1) resulted in the classic uncoupling of isoprene emissions (T.sub.opt,âiso â¯>â¯40⯰C) from net photosynthesis (T.sub.opt,âPn â=â30.0-32.5⯰C) with up to 7â¯% of Pn emitted as isoprene at 40⯰C. Under standard environmental conditions of PAR and leaf temperature, young V. guianensis leaves showed high methanol emissions, low Pn, and low isoprene emissions. In contrast, mature leaves showed high Pn, high isoprene emissions, and low methanol emissions, highlighting the differential control of leaf phenology over methanol and isoprene emissions. High daytime ambient isoprene concentrations (11â¯ppbv) were observed above a secondary Amazon rainforest, suggesting that isoprene emissions are common among neotropical pioneer species. The results are not consistent with the initial hypothesis and support a functional role of methanol during leaf expansion and the establishment of photosynthetic machinery and a protective role of isoprene for photosynthesis during high temperature extremes regularly experienced in secondary rainforest ecosystems.
Estimativa do Índice de Área Foliar (IAF) e Biomassa em pastagem no estado de Rondônia, Brasil Zanchi, Fabrício Berton(Vrije Universiteit Faculty of Earth and Life Sciences Department of Geo-Environmental Sciences,Universidade Federal do Amazonas Instituto Agricultura e Ambiente); Waterloo, Maarten J.(Vrije Universiteit Faculty of Earth and Life Sciences Department of Geo-Environmental Sciences); Aguiar, Leonardo J. G.(Universidade Ferderal de Rondônia) ...
Acta amazonica,
2009, Letnik:
39, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Medidas mensais da altura da pastagem, biomassa total, variações de biomassa viva e morta, a área específica foliar (SLA) e o Índice de Área de Folha (IAF) de fevereiro de 1999 a janeiro de 2005 na ...Fazenda Nossa Senhora (FNS) e em Rolim de Moura (RDM) entre Fevereiro a Março de 1999, Rondônia, Brasil. A pastagem predominante é Urochloa brizantha (Hochst. ex A. Rich) R. D. Webster (99% na FNS e 76% em RDM), com pequenas manchas de Urochloa humidicula (Rendle). A altura média anual da grama foi de ~0,16 m. Com o pastejo, o mínimo mensal foi de 0,09 m (estação seca) e máximo de 0,3 m sem pastejo (estação úmida). O IAF, biomassa total, material morto, vivo e SLA tiveram valores médios de 2,5 m² m-2 , 2202 kg ha-1, 2916 kg ha-1 e 19 m² kg-1 respectivamente. A média mensal da biomassa foi 4224 kg ha-1 em 2002 e 6667 kg ha-1 em 2003. Grande variação sazonal do material vivo e morto, sendo mais alto o vivo durante a estação úmida (3229 contra 2529 kg ha-1), sendo o morto maior durante a seca (2542 contra 1894 kg ha-1). O nível de água no solo variou de -3,1 a -6,5 m durante as estações. Em médias anuais os IAF foram de 1,4 em 2000 a 2,8 em 2003 e o SLA entre 16,3 m² kg-1 em 1999 e 20,4 m² kg-1 em 2001. As observações do Albedo variaram de 0,18 para 0,16 em relação aos altos valores de IAF.
Monthly measurements of the grass height, total above-ground biomass and the proportions of live and dead biomass, Specific Leaf Area (SLA) and Leaf Area Index (LAI) were made in one cattle ranch at the Fazenda Nossa Senhora (FNS) (February of 1999 to January of 2005) and also in Rolim de Moura (RDM) (February to March of 1999) in Rondônia state. The predominant grass species is Urochloa brizantha (Hochst. ex A. Rich) R. D. Webster (covering 99% of the area in FNS and 76% in RDM), with minor patches of Urochloa humidicula. This pasture was regularly grazed. The average grass height was 0.16 m but monthly value varied between 0.09 m after intensive grazing in the dry season to 0.32 m in a wet season without grazing. The LAI, total biomass, dead plant material, live above-ground plant material and SLA average 2,5 m² m-2, 2202 kg ha-1, 2916 kg ha-1 and 19 m² kg-1 respectively. The monthly average above-ground biomass showed little seasonal variation, but annual averages ranged from 4224 kg ha-1 in 2002 to 6667 kg ha-1 in 2003. Live biomass was significantly higher during the wet season than during the dry season (3229 versus 2529 kg ha-1) whereas dead biomass was higher during the dry season than during the wet season (2542 versus 1894 kg ha-1). The groundwater levels changes from -3.1 m to -6.5 m during the wet and dry seasons, respectively. The annual average of SLA was 16.3 m² kg-1 in 1999 and 20.4 m² kg-1 in 2001. And for LAI was 1.5 in 2000 to 2.8 in 2003. The Albedo changes from 0.18 down to 0.16 at higher values of LAI.
This research aims to assess air quality in a transitional location between city and forest in the Amazon region. Located downwind of the Manaus metropolitan region, this study is part of the ...large-scale experiment GoAmazon2014/5. Based on their pollutant potential, inhalable particulate matter (PM
), nitrogen dioxide (NO
), sulfur dioxide (SO
), ozone (O
), hydrogen sulfide (H
S), benzene, toluene, ethylbenzene and meta-, orto-, para-xylene (BTEX) were selected for analysis. Sampling took place during the wet season (March-April 2014) and dry season (August-October 2014). The number of forest fires in the surroundings was higher during the dry wet season. Results show significant increase during the dry season in mass concentration (wet: <0.01-10 μg m
; dry: 9.8-69 μg m
), NH
soluble content (wet: 13-125 μg m
; dry: 86-323 μg m
) and K
soluble content (wet: 11-168 μg m
; dry 60-356 μg m
) of the PM
, and O
levels (wet: 1.4-14 μg m
; dry: 1.0-40 μg m
), indicating influence of biomass burning emissions. BTEX concentrations were low in both periods, but also increased during the dry season. A weak correlation in the time series of the organic and inorganic gaseous pollutants indicates a combination of different sources in both seasons and NO2 results suggest a spatial heterogeneity in gaseous pollutants levels beyond initial expectations.
Atmospheric turbulence characteristics within and above rain forest canopies are investigated at several sites located in the Amazon region of Brazil. Turbulence data provided by bi- and ...three-dimensional sonic anemometers, which were deployed at heights ranging from near the forest floor to about 80 m, are analyzed to describe the principal features of atmospheric turbulence, sensible heat flux (H), and components of the turbulent kinetic energy (TKE) budget equation. The analyses focused on weak (WW) and strong (SW) wind conditions to achieve the research objectives of evaluating the turbulence structure above and below the rain forest canopy and estimating the degree of coupling between air layers above the forest and deep in the canopy. Turbulence statistical moments show that atmospheric eddies, generated above the canopy, hardly penetrate the region below 0.5h (h is the canopy height). Forest-atmosphere exchanges of heat differ depending on the observed wind regimes. Sensible heat fluxes decrease with canopy depth for SW conditions and are approximately constant with the height for WW above the canopy. Sensible heat flux profiles reveal a transition layer (around 0.6h) which sometimes exchanges heat with the upper and sometimes with the lower forest canopy, depending on time of day and weather conditions. TKE balance results show that during the daytime period in SW conditions the shear production is at least an order of magnitude greater than the buoyancy above the forest canopy. This turbulence, however, is practically all dissipated in the region above 0.5h. Thus, the air layer from the soil surface to 0.5h is largely decoupled from the upper part of the forest canopy. This feature of having the bottom of the canopy mostly decoupled from the air aloft in the dense and tall rain forest can exert control on the residence times and turbulent transport of plant-emitted gases out of the forest canopy.
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