Circulação De Brisa Fluvial E a Banda De Precipitação Na Margem Leste Da Baía De Marajó

Abstract

ResumoNa região de Belém, além dos sistemas atmosféricos de grande escala como a ZCIT e de mesoescala como as Linhas de Instabilidade, há também sistemas convectivos forçados localmente que também causam precipitação. Este trabalho estuda um sistema convectivo, observado pela primeira vez nessa região durante a campanha do projeto CHUVA, o qual é denominado por Microlinha de Instabilidade Fluvial(MLF) devido sua formação estar associada a circulação de brisa fluvial. Os dados do satélite GOES 12, radar banda X, anemômetro de hélice, pluviômetros, disdrômetros, reanálises do NCEP foram utilizados para estudar esta MLF. Simulação numérica de alta resolução com o modelo BRAMS foi feita para esta MLF, utilizando-se duas grades com resolução horizontal de 3 Km e 1 Km. Os resultados da simulação mostraram que a MLF foi formada através de brisa fluvial proveniente da baía de Marajó, causando precipitação desde sua fase inicial sobre a região de Belém até quando estava sobre a margem oeste da baía do Marajó. Durante sua propagação para Oeste, observou-se aumento da sua intensidade, que foi máxima sobre a baía de Marajó, onde há intenso transporte de cargas e passageiros e naufrágios são o tipo de acidente mais frequente. Palavras-chave: Microlinha. Refletividade. Brisa fluvial. BRAMS. AbstractThe precipitation in Belem region is mainly due the large atmospheric systems such as ITCZ and mesoscale systems like the Instability Lines. Beside these systems, there are convective systems forced locally which also promote precipitation in this region. This paper studies a convective system, observed for first time during the campaign of the RAIN project, which is called Micro Instability Line Fluvial (MLF) because its formation is associated with river breeze circulation. The GOES 12 satellite data, radar band X, anemometer, rain gauges, disdrometer, and NCEP reanalyzes were used to study this MLF. High-resolution numerical simulation with the BRAMS model was made for this MLF, using two grids with horizontal resolution of 3 km and 1 km. The simulation results showed that the MLF was formed by river breeze from the Marajo Bay, causing precipitation since the early stages in Belem area until this MLF was on the west bank of the Marajo bay. During its propagation westward, this MLF had increased its intensity, which was maximum over the Bay of Marajo, where there is intense transportation of cargo and passengers, and shipwrecks are the most frequent type of accidents.

Local Circulation Features in the Eastern Amazon: High-resolution Simulation

“…The wind direction and speed are well-represented, except for the maxima, which are generally not well-represented in the wind speed. The model has also shown a delay in BB onset of approximately 2 h in Castanhal, which was also observed by Matos and Cohen (2016). Regarding the temperature at the surface, the diurnal cycle was well represented by the model for the four localities studied.…”

“…It is also worth noticing that wind phase change, associated with breeze onset, in the series is slightly delayed if compared to the observed; wind rotation, associated with the onset of BB, is delayed approximately 2 h in WRF compared to the observed. Matos and Cohen (2016) also find a delay in the formation of BB in BRAMS model. It is important to emphasize that Castanhal is at a point of juxtaposition between SB and BB.…”

“…10e), which exceeds 3 km and is related to the SB channeling effect that occurs on Marajó Bay. Matos and Cohen (2016) detected the same channeling effect of the wind on Marajó Bay.…”

Analysis of the breeze circulations in Eastern Amazon: an observational study

“…Therefore, this influence becomes much bigger than the oceanic effect on the SB. Other studies have shown the presence of the RB in Amazonian cities (Silva Dias et al , ; Fitzjarrald et al , ; Cohen et al, ; Santos et al , ; Matos and Cohen, ); generally this temperature contrast between the forest and the rivers can reach more than 6 °C (Greco et al , ; Oliveira and Fitzjarrald, ).…”

“…The Eastern Amazon (Figure for the geographical location of the target area in this study) observes a variety of mesoscale convective systems, among which we can highlight mesoscale convective complex (CCMs) and squall lines (SLs) (Kousky, ; Maddox, ; Cohen et al , ; Vitorino et al , ; Silva Dias et al , ; Lu et al , ; Fitzjarrald et al , ; Ramos da Silva et al , ; Cohen et al , ; Matos and Cohen, ).…”