Assessment of the variability of pollutants concentration over the metropolitan area of São Paulo, Brazil, using the wavelet transform

Abstract

The objective of this work was to investigate the mean and variability of a dataset of pollutant concentrations from measurements taken over the metropolitan area of São Paulo city, Brazil. Wavelet analysis was applied to the time series of pollutant concentrations, revealing the strongest harmonics influencing the signals. A mode of variability of 4-8 days was significant until the middle of the last decade and is likely associated with the approach and passage of meteorological systems. A dataset representing the number of frontal systems moving across the state helped to explain the interannual variability during wintertime. Years with fewer frontal systems had higher levels of pollutants in several locations. Weather events such as inversions and the passage of frontal systems influence the concentration of pollutants. Public policies on air quality should focus not only on reducing the long-term exposure of city-dwellers to the negative effects of pollutants but also account for the possible short-term effects of the weather on air quality.

Evaluating the variability, transport and periodicity of particulate matter over smart city Bhubaneswar, a tropical coastal station of eastern India

“…Continuous wavelet transform (CWT) scalogram is a tool for determining dominant modes within a time series by decomposing the time series into the time-frequency domain [44,56,62]. In the present study, the periodicity test is performed on hourly data sets using Morlet mother wavelet, normalised by the standard deviation.…”

Atmospheric Pollution Reduction in São Paulo City and the Social Isolation Effect

“…The municipality of São Paulo is located in the southeast portion (23.5477ºS; 46.6336º W) of the state of São Paulo and has a territorial area equal to 1,521 km 2 ( Figure 1). In population estimative for July 2019, São Paulo is classified as the most populated municipality in Brazil, with 12.25 million inhabitants (IBGE, 2019;ZERI et al, 2016). Economically, it presents a large industrial district, dominated mainly by food, chemical and oil industries.…”

“…In the summer, the South Atlantic Convergence Zone (SACZ) and the Mesoscale Convective Systems (SCM) are main drivers for precipitation and greater atmospheric instability. In winter, due to the reduction of precipitation and the occurrence of thermal inversions, the atmosphere tends to acquire a greater stability, which causes the stagnation of atmospheric pollutants from industrial activities and from the burning of fuels in the lower atmospheric layers and near the surface (Vieira-Filho et al 2015;Segalin et al 2016;Zeri et al 2016).…”

Exposure assessment of rainfall to interannual variability using the wavelet transform

“…The advantage of the technique is that intermittent influences are better identified in comparison with the traditional Fourier transform, which is based on sine and cosine functions that extend over the whole record. The wavelet transform has been used in many studies recently, including the characterization of turbulence over plant canopies (Collineau and Brunet, ; Krusche and De Oliveira, ), variability of pollutants concentrations (Zeri et al, ) and climate studies, among others (Torrence and Compo, ; Grinsted et al, ; Labat et al, ; Apaéstegui et al, ).…”