Severe Convection Features in the Amazon Basin: A TRMM-Based 15-Year Evaluation

Nunes, Ana Maria Pereira; Dias, Maria A. F. Silva; Anselmo, Evandro M.; Morales, Carlos A.

doi:10.3389/feart.2016.00037

Cited by 26 publications

(43 citation statements)

References 69 publications

(101 reference statements)

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“…In general, we found that the rainy season (SONDJF) has a higher occurrence of windthrows than the dry season (MAMJJA), a pattern concurrent with extreme convection (highest in OND, lowest in AMJ) in Central Amazonia [57]. Seasonal rainfall is regulated by the South American Monsoon System (SAMS) [58][59][60].…”

Section: Discussionmentioning

confidence: 90%

Windthrow Variability in Central Amazonia

et al. 2017

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Windthrows are a recurrent disturbance in Amazonia and are an important driver of forest dynamics and carbon storage. In this study, we present for the first time the seasonal and interannual variability of windthrows, focusing on Central Amazonia, and discuss the potential meteorological factors associated with this variability. Landsat images over the 1998-2010 time period were used to detect the occurrence of windthrows, which were identified based on their spectral characteristics and shape. Here, we found that windthrows occurred every year but were more frequent between September and February. Organized convective activity associated with multicell storms embedded in mesoscale convective systems, such as northerly squall lines (that move from northeast to southwest) and southerly squall lines (that move from southwest to northeast) can cause windthrows. We also found that southerly squall lines occurred more frequently than their previously reported~50 year interval. At the interannual scale, we did not find an association between El Niño-Southern Oscillation (ENSO) and windthrows.

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Section: Discussionmentioning

confidence: 90%

Windthrow Variability in Central Amazonia

et al. 2017

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“…We made this selection considering preferred locations with reported concentrations of intense convective storms (Velasco and Frisch, 1987;Zuluaga and Poveda, 2004;Zipser et al, 2006;Romatschke and Houze, 2010;Rasmussen and Houze, 2011;Zuluaga and Houze, 2015;Rasmussen et al, 2016). With few exceptions (Nunes et al, 2016), little effort has been made to understand the differences between PFs among different sub-regions of the Amazon River Basin, characterized by a different hydro-climatology and vegetation cover. Therefore, we aim to further disentangle the PFs among these sub-regions.…”

Section: Study Regionsmentioning

confidence: 99%

Mesoscale convective systems and other precipitation features over the tropical Americas and surrounding seas as seen by TRMM

Jaramillo

Poveda

Mejía

2017

Intl Journal of Climatology

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We classified and characterized precipitation features (PFs) at annual and diurnal timescales during 1998–2011 over the tropical Americas and adjoining oceans using data from two instruments on board the Tropical Rainfall Measuring Mission (TRMM). Our scope included geographic distribution, frequency, area, rainfall rate, and polarization‐corrected temperatures (PCTs) of PFs in an effort to contrast different regions over Colombia, the Amazon River Basin, and the adjoining oceanic regions (Pacific Ocean and Caribbean Sea). Our results showed that mesoscale convective systems (MCSs) over the Caribbean Sea exhibited colder minimum PCTs than Pacific Ocean MCSs. Pacific Ocean MCSs had higher rainfall rates, however, than Caribbean Sea MCSs. Despite the fact that MCSs represented <1% of the total precipitation systems found, the MCSs contributed more rainfall over the study regions. Over the Pacific Ocean, for example, MCSs contributed approximately 57% of the total rainfall contributed by all precipitation systems identified over that region. Additionally, MCSs over the Pacific coast have their maximum frequency during the morning hours (0000–0600 Local Time) offshore and centred over the Pacific Ocean at 77.5°W. The annual cycle of PFs showed a marked bimodal annual cycle over Colombia, whereas over the Amazon Basin, Pacific Ocean, and Caribbean Sea, PFs were characterized by a unimodal annual cycle.

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“…In cloud processing (e.g., Hoppel et al, 1994;Lee et al, 2004) in shallow convective clouds and particle formation through heterogeneous pathways (Jang et al, 2002;Lim et al, 2005;Limbeck et al, 2003) are possible mechanisms contributing to the presence of Aitken mode particles in the lower free troposphere. The downward transport of particles from the lower free troposphere to the BL can occur either through convective downdrafts , typically observed in Amazonia (Machado et al, 2004;Nunes et al, 2016), or through continuous entrainment. Previous studies reported heights of 1500 to 2500 km as the probable level of the origin of convective downdraft events in Amazonia (Betts et al, 2002;Schiro and Neelin, 2018).…”

Section: Introductionmentioning

confidence: 99%

Multi-year statistical and modeling analysis of submicrometer aerosol number size distributions at a rain forest site in Amazonia

et al. 2018

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Abstract. The Amazon Basin is a unique region to study atmospheric aerosols, given their relevance for the regional hydrological cycle and the large uncertainty of their sources. Multi-year datasets are crucial when contrasting periods of natural conditions and periods influenced by anthropogenic emissions. In the wet season, biogenic sources and processes prevail, and the Amazonian atmospheric composition resembles preindustrial conditions. In the dry season, the basin is influenced by widespread biomass burning emissions. This work reports multi-year observations of high time resolution submicrometer (10-600 nm) particle number size distributions at a rain forest site in Amazonia (TT34 tower, 60 km NW from Manaus city), between 2008 and 2010 and 2012 and 2014. The median particle number concentration was 403 cm −3 in the wet season and 1254 cm −3 in the dry season. The Aitken mode (∼ 30-100 nm in diameter) was prominent during the wet season, while the accumulation mode (∼ 100-600 nm in diameter) dominated the particle size spectra during the dry season. Cluster analysis identified groups of aerosol number size distributions influenced by convective downdrafts, nucleation events and fresh biomass burning emissions. New particle formation and subsequent growth was rarely observed during the 749 days of observations, similar to previous observations in the Amazon Basin. A stationary 1-D column model (ADCHEMAerosol Dynamics, gas and particle phase CHEMistry and radiative transfer model) was used to assess the importance of the processes behind the observed diurnal particle size distribution trends. Three major particle source types are required in the model to reproduce the observations: (i) a surface source of particles in the evening, possibly related to primary biological emissions; (ii) entrainment of accumulation mode aerosols in the morning; and (iii) convective downdrafts transporting Aitken mode particles into the boundary layer mostly during the afternoon. The latter process has the largest influence on the modeled particle number size distributions. However, convective downdrafts are often associated with rain and, thus, act as both a source of Aitken mode particles and a sink of accumulation mode particles, causing a net reduction in the median total particle number concentrations in the surface layer. Our study shows that the combination of the three mentioned particle sources is essential to sustain particle number concentrations in Amazonia.

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Severe Convection Features in the Amazon Basin: A TRMM-Based 15-Year Evaluation

Cited by 26 publications

References 69 publications

Windthrow Variability in Central Amazonia

Windthrow Variability in Central Amazonia

Mesoscale convective systems and other precipitation features over the tropical Americas and surrounding seas as seen by TRMM

Multi-year statistical and modeling analysis of submicrometer aerosol number size distributions at a rain forest site in Amazonia

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