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The main features of low‐level jet (LLJ) in the metropolitan region of São Paulo (MRSP), Brazil, are assessed using rawinsondes carried out: (a) every 3‐hr during 10‐consecutive days in summer and winter field campaigns of the MCITY BRAZIL Project in 2013, (b) at 0900 and 2100 local time, from September 2009 to August 2013. These observations indicate that the LLJ is a typical feature of the MRSP, observed in 85% of the 20 days of the field‐campaigns and 77.6% of the 1,446 days of regular rawinsonde period. The fine temporal and spatial resolution soundings indicate that most of the LLJs occur during nighttime and early in the morning, with mean intensity of 8.5 ± 0.3 m s−1, height of 539 ± 26 m, and mostly (52.5%) from east and north. The coarse resolution soundings indicate the LLJ display a seasonal variation with maximum intensity in October (8.6 ± 0.3 m s−1) and a minimum in February (7.1 ± 0.2 m s−1), a maximum height in March (703 ± 151 m) and a minimum in June (577 ± 151 m). During MCITY campaigns about 76.4% of LLJ events show inertial oscillation and 35.3% of them are combined with sea breeze. Only 17.6% of LLJ events are associated with cold fronts and post‐frontal high pressure system. The urban heat island intensity, surface inversion layer strength, particulate matter 2.5 and carbon monoxide concentrations are negatively correlated with the LLJ intensity, suggesting the jet‐induced turbulent mixing may contribute to reduce them. Key Points: The low‐level jet (LLJ) is a remarkable robust feature of metropolitan region of São Paulo climate, occurring in more than 77% of timeThey occur during nighttime, under less disturbed synoptic conditions and more often in association to sea‐breeze circulationMost of LLJ display inertial oscillation and are correlated with urban heat island, surface inversion layer, and air pollution [ABSTRACT FROM AUTHOR]

This paper presents the graphical results of the Lagrangian-model and the weathering processes associated with oil spills in the tropical South Atlantic, taking into account the meteorological and oceanographic conditions of the study region. The scenarios were created in the Brazilian-NE waters adjacent, with simulation times of 670 h, and densities of 35, 25, and 15API with volume of 1590 m3 were considered. The main results showed that the meteo-oceanographic characteristics of the study region influence the trajectories and weathering processes in the oil spill. The trajectories varied for each launch point and reached the continent severely in January and October. The associated weathering processes showed higher rates in September and lower rates in April, indicative of the influence of phenomena such as Intertropical Tropical Convergence Zone and warm pool in the South Atlantic region. Sea surface temperature and wind speed are key factors that correlate positively with these months. [Display omitted] • Evaporation, dispersion and water content in the oil show different temporal patterns in April and September. • Wind intensity, wave energy and SST affect weathering processes. • The trajectories change according to the zonal component towards the continent. [ABSTRACT FROM AUTHOR]

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Flow-Topography Interaction can be considered as a particular set of processes resulting of the currents interaction with a topographic gradient, specially associated with submarine canyon areas, which are important morphological features with potential to upwelling and cross-isobath transport on the continental margins. The South Pernambuco Continental Shelf (SPCS) and Pernambuco Plateau located on the Southwestern Tropical Atlantic (SWTA), present incised morphological features, highlighting the shelf valleys and blind canyons, which do not have a connection to the shelf or an onshore river system. They are likely features for interactions between the dominant along-shelf flow represented by the strong western boundary North Brazil Undercurrent. We investigated potential canyon induced upwelling and the respective mechanisms at the late spring/early fall context. CTD and reanalysis data from GLORYS12V1, and in situ bathymetric measurements were used to characterise the hydrodynamics and canyon morphology, respectively. Then, we combined both to obtain dimensionless numbers from dynamical scale analysis to infer possible imbalances of the acting forces. Reanalysis data evidenced uplift at the slope not related to the blind canyons. CTD data indicated a seasonal variation of the intrusion of water masses, especially at the shelf-break for the Middle shelf valley and Campas shelf valley. A temperature difference of 2.5 °C (2.0 °C) between surface and deep waters was observed during the late spring. A stepwise temperature structure was present in both seasons, indicating instability below the mixed layer depth, the uplifting of isotherms, and the corrosion of the lower portion of the surface mixed layer. The dimensionless parameters analysis reveals highest Rossby values during the fall, mainly in Zieta shelf valley (R 0 =130.87) and Csv (R 0 =111.71), and lower values for the canyons of the Pernambuco Plateau. Our hypothesis is that the shelf valleys might play a role in conducting the uplifted slope water coast-ward. For the blind canyons, although no related upwelling was observed, reanalysis revealed the presence of a deep anti-cyclonic eddy at one of the blind canyon's mouth. Rossby and Burger numbers indicate a weak geostrophic balance at the canyon rim, and instability of the horizontal length scale of the pressure gradient force, with tendency to vorticity control. While the paradigm that shelf and coastal waters off north-eastern Brazil are mostly oligotrophic in the surface is true, our observation of shallow (<60 m) subsurface uplift should be considered in future works in the SWTA. [Display omitted] • Flow-topography interaction is investigated at the western Atlantic boundary. • 105 CTD profiles has indicate colder water masses intrusion over the shelf-break. • Dimensionless numbers confirm the shoreward transport through shelf valleys. • Slope uplift transport was identified instead upwelling process. [ABSTRACT FROM AUTHOR]