Pilot Analysis of Hourly Rainfall in Central and Eastern Amazonia

Cutrim, Elen; Martin, David W.; Butzow, Dean G.; Silva, Isa M.; Yulaeva, E.

doi:10.1175/1520-0442(2000)013<1326:paohri>2.0.co;2

Cited by 30 publications

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Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

“…Specifically over the eastern coast of the Amazon, it has been found that peaks of rainfall tend to occur at 05:00 h LST in Marajó Island and at 17:00 h LST in Belém (Kousky 1980). In the central Amazon, near the convergence between the Amazonas and Negro rivers and over the Reserva Florestal Ducke, located at 25 km from Manaus, peaks of precipitation occur at 12:00 and 15:00 h LST, respectively (Lloyd 1990, Cutrim et al 2000.Despite the low rain-gauge density over the Amazon Basin, the pluviometers in that area are sufficient to allow evaluation of some rainfall characteristics and also to be very useful as ground truth for satellite applications. The main purpose of the present study is to analyse 3 yr of previously unavailable rain-gauge data over the Brazilian Amazon so as to increase knowledge of the diurnal variations of rainfall over this area.…”

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Diurnal cycle of rainfall over the Brazilian Amazon

Angelis¹,

McGregor

Kidd

2004

Clim. Res.

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The rainfall characteristics over the Brazilian Amazon were analysed using 3 yr of 3 h data from 24 rain gauges. During this period, areas in the eastern sector experienced up to 22% of rainy hours, while those in the southern sector recorded up to 7%. In the northern Amazon, rain tends to occur during the night, while in southern, central and central-western Amazon it occurs mainly in the afternoon. In contrast, over the eastern Amazon, rain occurs late at night and early in the morning. Harmonic analysis revealed an increase in the phase of the first harmonic phase from eastern towards central Amazon, suggesting that the rain propagates in that direction. The amplitude of the first and second harmonics revealed the existence of a relatively dry area inland about 500 km from the Atlantic coast. This area seems to be the limit for the inland penetration of systems originating at the coast. The phase of the first harmonic revealed small differences between the diurnal cycles of rainfall during the wet and dry seasons, suggesting that there is no difference between low-level circulations in either season. KEY WORDS: Amazon · Diurnal cycle · Rainfall · Precipitation · Rain gauge Resale or republication not permitted without written consent of the publisherClim Res 26: [139][140][141][142][143][144][145][146][147][148][149] 2004 noon, from about 15:00 to 19:00 h LST (Dai 2001). The phase of convective activity over land in the South and Central Americas, South and Central Africa, India and Borneo is generally from late afternoon to evening (Houze et al. 1981, Hendon & Woodberry 1993, Yang & Slingo 2001. Specifically over the eastern coast of the Amazon, it has been found that peaks of rainfall tend to occur at 05:00 h LST in Marajó Island and at 17:00 h LST in Belém (Kousky 1980). In the central Amazon, near the convergence between the Amazonas and Negro rivers and over the Reserva Florestal Ducke, located at 25 km from Manaus, peaks of precipitation occur at 12:00 and 15:00 h LST, respectively (Lloyd 1990, Cutrim et al. 2000.Despite the low rain-gauge density over the Amazon Basin, the pluviometers in that area are sufficient to allow evaluation of some rainfall characteristics and also to be very useful as ground truth for satellite applications. The main purpose of the present study is to analyse 3 yr of previously unavailable rain-gauge data over the Brazilian Amazon so as to increase knowledge of the diurnal variations of rainfall over this area. DATA AND ANALYSIS METHODThe nature of the diurnal rainfall cycle was established using harmonic analysis, which yields information about the amplitude and phase (timing) of the peak in a time series. The methodology followed is that outlined by Wilks (1995). Accordingly, rainfall is modelled at time t in a series y by the harmonic function:where y is the mean of the series, n is the period, C is the amplitude, φ is the phase and k is the harmonic number. The amplitude C is estimated by:(2) where A 1 = 2/n × Σy t cos(2πt/n) (3)The phase can then be derived...

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Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

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confidence: 99%

Diurnal cycle of rainfall over the Brazilian Amazon

Angelis¹,

McGregor

Kidd

2004

Clim. Res.

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“…Greco et al (1990) found that instability line that reached Manaus during ABLE-2B were responsible for 40% of directly observed rainfall. The somewhat reduced nocturnal convective activity still brings appreciable rainfall to the region (Cutrim et al, 2000;Angelis et al, 2004, Kousky et al, 2006. We take advantage of the natural temporal partition of rainfall types: local rainfall falls in the afternoon, with primarily instability line stimulated rainfall at night.…”

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confidence: 99%

Radar-observed spatial and temporal rainfall variability near the Tapajós-Amazon confluence

Cohen

Fitzjarrald

D'Oliveira

et al. 2014

Rev. bras. meteorol.

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Standard Amazonian rainfall climatologies rely on stations preferentially located near river margins. River breeze circulations that tend to suppress afternoon rainfall near the river and enhance it inland are not typically considered when reporting results. Previous studies found surprising nocturnal rainfall maxima near the rivers in some locations. We examine spatial and temporal rainfall variability in the Santarém region of the Tapajós-Amazon confluence, seeking to describe the importance of breeze effects on afternoon precipitation and defining the areal extent of nocturnal rainfall maxima. We used three years of mean S band radar reflectivity from Santarém airport with a Z-R relationship appropriate for tropical convective conditions. These data were complemented by TRMM satellite rainfall estimates. Nocturnal rainfall was enhanced along the Amazon River, consistent with the hypothesis that these are associated with the passage of instability lines, perhaps enhanced by local channeling and by land breeze convergence. In the daytime, two rainfall bands appear in mean results, along the east bank of the Tapajós River and to the south of the Amazon River, respectively. Keywords : Precipitation, River Breeze, Instability Lines. RESUMO: VARIABILIDADE ESPACIAL E TEMPORAL DA PRECIPITAÇÃOOBSERVADA COM O RADAR NA CONFLUENCIA DO TAPAJÓS E AMAZONAS Na Amazônia as series climatológicas estão baseadas na rede de estações meteorológicas de superfície que estão instaladas preferencialmente nas margens de rios. Portanto, o efeito de brisas fluviais que promovem precipitação no interior do continente não está sendo contabilizado nas medidas realizadas nestas estações. Além disto, estudos anteriores encontraram máximo de precipitação no período noturno sobre rios. Assim, este artigo examina a variabilidade espacial e temporal da precipitação na região de confluência dos rios Tapajós e Amazonas em Santarém, visando descrever a importância da brisa fluvial na distribuição da precipitação durante a tarde e definir a extensão da área onde ocorre maxima precipitação no período noturno. A refletividade medida pelo radar meteorológico banda S, instalado em Santarém para um período de três anos foi utilizada, tendo estes dados sido calibrados através dos dados do sensor de precipitação instalado abordo do satélite TRMM. A intensidade de precipitação foi estimada utilizando a relação ZR para o caso convectivo tropical. No período noturno, a máxima precipitação foi encontrada ao longo do rio Amazonas, consistente com a hipótese de que esta precipitação estaria associada a passagem das linhas de instabilidade neste período, talvez esta precipitação também esteja sendo reforçada pela canalização do rio e pela confluência do vento de retorno da brisa fluvial durante a noite. Para o período diurno, observou-se duas bandas de precipitações localizadas no interior do continente, uma ao longo da margem leste e outra ao sul dos rios Tapajós e Amazonas, respectivamente. Palavras-chave: Precipitação, Brisa Fluvial, Linhas de Instabili...

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“…Many efforts have been made to observe and to understand the diurnal cycle over the Amazon basin using surface observations (e.g., Harriss et al, 1990;Cutrim et al, 2000;Machado et al, 2004;Tanaka et al, 2014) or satellite data (e.g., Minnis and Harrison, 1984;Janowiak et al, 2005;Burleyson et al, 2016). The diurnal cycle over the Amazon basin is complex because it is affected by three types of convective systems : locally occurring systems (LOS) generated locally in the form of small convective cells (area less than 1000 km 2 ) with short lifetime (on the order of 1 h), coastal-occurring systems (COS) initialized at the northeast coast of Brazil by the sea breeze and propagating inland as squall lines and basin-occurring systems (BOS) initialized in the Amazon basin in the form of mesoscale convective systems (MCSs) with areas larger than 1000 km 2 .…”

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Large-scale vertical velocity, diabatic heating and drying profiles associated with seasonal and diurnal variations of convective systems observed in the GoAmazon2014/5 experiment

et al. 2016

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Abstract. This study describes the characteristics of largescale vertical velocity, apparent heating source (Q 1 ) and apparent moisture sink (Q 2 ) profiles associated with seasonal and diurnal variations of convective systems observed during the two intensive operational periods (IOPs) that were conducted from 15 February to 26 March 2014 (wet season) and from 1 September to 10 October 2014 (dry season) near Manaus, Brazil, during the Green Ocean Amazon (GoAmazon2014/5) experiment. The derived large-scale fields have large diurnal variations according to convective activity in the GoAmazon region and the morning profiles show distinct differences between the dry and wet seasons. In the wet season, propagating convective systems originating far from the GoAmazon region are often seen in the early morning, while in the dry season they are rarely observed. Afternoon convective systems due to solar heating are frequently seen in both seasons. Accordingly, in the morning, there is strong upward motion and associated heating and drying throughout the entire troposphere in the wet season, which is limited to lower levels in the dry season. In the afternoon, both seasons exhibit weak heating and strong moistening in the boundary layer related to the vertical convergence of eddy fluxes.A set of case studies of three typical types of convective systems occurring in Amazonia -i.e., locally occurring systems, coastal-occurring systems and basin-occurring systems -is also conducted to investigate the variability of the large-scale environment with different types of convective systems.

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Pilot Analysis of Hourly Rainfall in Central and Eastern Amazonia

Cited by 30 publications

References 0 publications

Diurnal cycle of rainfall over the Brazilian Amazon

Diurnal cycle of rainfall over the Brazilian Amazon

Radar-observed spatial and temporal rainfall variability near the Tapajós-Amazon confluence

Large-scale vertical velocity, diabatic heating and drying profiles associated with seasonal and diurnal variations of convective systems observed in the GoAmazon2014/5 experiment

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