Rawinsonde‐Based Analysis of the Urban Boundary Layer in the Metropolitan Region of São Paulo, Brazil

Abstract

The main features of the urban boundary layer in the metropolitan region of São Paulo are estimated based on rawinsondes carried out (a) every 3 hr in two 10‐day field campaigns of the MCITY BRAZIL Project during the summer and winter of 2013 and (b) regularly once per day and continuously for 4 years from 2009 to 2013. On average, the boundary layer height showed a daytime maximum of 1476 ± 149 m in summer and 1122 ± 168 m in winter campaigns. The differences are related to seasonal variations in the (a) buoyancy flux at the surface, which was 30% larger in summer (4.7 ± 0.6 MJ m−2 day−1), and the (b) static stability of the free atmosphere, which was 15% smaller in summer (3.3 ± 0.1 K km−1). The average nighttime boundary layer height, estimated from equilibrium empirical expression, indicated maximum of 126 ± 13 m in summer and 122 ± 10 m in winter campaigns. The presence of a low‐level jet was identified in 80% of the field campaign nights, with intensity varying from 2.7 to 14 m s−1 and height ranging from 95 to 962 m. The nighttime residual‐mixing layer is well estimated using the air temperature gradient method and is a good indication of the maximum vertical evolution of the previous daytime boundary layer. The monthly average maximum boundary layer height varied from a minimum of 1,061 ± 77 m in September to maximum of 1,632 ± 96 m in May.

Air pollutants associated with surface meteorological conditions in São Paulo’s ABC region

“…The climate at MASP, including the ABC region, is classified as high elevation subtropical humid (Cwb), according to the Köppen classification (Piñero Sánchez et al, 2020). The winter at the ABC region is dry and mildly cold, with a mean temperature of 16.7°C and 74.5% relative humidity (RH) in July.…”

“…The highest monthly rainfalls occur in the summer, reaching 242 mm.month -1 in January on average, while August is typically the month with the lowest amount of rainfall, 26 mm.month -1 (Valverde et al, 2020). The planetary boundary layer (PBL) height at MASP shows a daytime maximum of about 1,500 m in the summer and 1,100 m in the winter, related to seasonal variations in the heat fluxes at surface (Piñero Sánchez et al, 2020). The seasonality of large-scale circulation at MASP is influenced by the dynamics of the South Atlantic Subtropical Anticyclone (SASA), which is zonally wider and closer to the continent in the austral winter and retracted to the east during the summer (Reboita et al, 2019).…”

“…In the winter, surface anticyclonic circulation predominates at MASP, and postfrontal high-pressure systems moving northeast typically merge with SASA. This winter synoptic pattern inhibits cloud formation and provides increased atmospheric stability, leading to a higher frequency of thermal inversions and restrictions on the air pollutant dispersion at MASP (Piñero Sánchez et al, 2020;Gozzo et al, 2021;Oliveira et al, 2021).…”

“…This is the closest available WMO meteorological station, with distances to the air quality monitoring stations ranging from 4 to 15 km ( Figure 1). Previous studies have shown that measurements of temperature, precipitation and relative humidity at IAG-USP station are representative within this spatial scale (Sugahara et al, 2012;Piñero Sánchez et al, 2020). The following surface variables were used in this study: air temperature (T), relative humidity (RH), wind speed (WS), global radiation (RAD) and precipitation.…”

Implantation, Operation Data and Performance Assessment of An Urban Area Grid-Connected Small Wind Turbine

“…Due to the intense dynamics of the air masses, large-scale and local circulations, and seasonal and even daily changes disturb the weather conditions[19]. São Paulo has weak predominance surface winds throughout the year, with speeds varying from minimum of 1.7 m/s to 2.3 m/s in May to maximum of 2.3 m/s to 3.1 m/s in November[20].Figure4shows a map plotted from[21]. At the SWT location point (pin), the mean average wind speed at 50 m height is 3 m/s.…”