ABSTRACT The Amazon region is one of the most pristine continental areas whose concentrations of atmospheric trace gases and aerosol particles are very low, mainly in the wet season. This study provides observational results of aerosol optical and radiative characteristics in situ as well as atmospheric columnar at a pristine forest in Central Amazonia. Spectral variation of the aerosol properties (aerosol optical depth [AOD], single scattering albedo [SSA], and asymmetry parameter [AP]) was evaluated using the AErosol RObotic NETwork (AERONET) data. The SSA values under natural atmospheric column conditions (AERONET) were compared to the SSA values calculated with in situ measurements. The values of shortwave aerosol radiative forcing (SWARF) on top of the atmosphere (TOA) and the surface (SUR) were estimated using the SBDART model and were validated with the AERONET values with regression analysis. SWARF had a high correlation to TOA (0.97) and SUR (0.92), including dry and wet seasons. Monthly, seasonal and annual mean values of SWARFTOA and SWARFSUR were negative while SWARFATM values were positive. SWARFTOA was -9.18 ± 2.80 W m-2 and SWARFSUR was -20.77 ± 5.04 W m-2 in the dry season, inducing a heating rate (HR) of 0.37 ± 0.13 K.day-1. This study showed that, for a long series of measurements, the effects caused by aerosols on the radiative flux in the pristine forest of Central Amazonia were of the order of SWARFTOA of -3.66 ± 1.59 W m-2 and SWARFSUR of -11.86 ± 2.35 W m-2 during the wet season.

RESUMEN La región del Amazonas es una de las áreas continentales más impolutas, cuyas concentraciones de gases traza atmosféricos y partículas de aerosol son muy bajas, sobre todo en la estación húmeda. El presente estudio proporciona resultados observacionales in situ tanto de las características ópticas y radiativas como de la columna atmosférica de los aerosoles en un bosque virgen de la Amazonia Central. Se evaluó la variación espectral de las propiedades de los aerosoles (profundidad óptica de aerosoles [AOD, por sus siglas en inglés], albedo de dispersión simple [SSA] y parámetro de asimetría [AP]) utilizando para ello datos de la Red Robótica de Aerosoles (AERONET). Los valores de SSA en condiciones naturales de la columna atmosférica (obtenidos de AERONET) se compararon con valores de SSA obtenidos de mediciones in situ. Se estimaron los valores del forzamiento radiativo de onda corta (SWARF) en el techo de la atmósfera (TOA) y en la superficie (SUR) con datos del modelo SBDART y se validaron con valores de AERONET utilizando análisis de regresión. Los valores de SWARF tuvieron una alta correlación con los de TOA (0.97) y SUR (0.92), incluyendo las temporadas húmeda y seca. Los valores promedio mensuales, estacionales y anuales de SWARFTOA y SWARFSUR fueron negativos, en tanto que los de SWARFATM fueron positivos. Los valores de SWARFTOA fueron de -9.18 ± 2.80 W m-2 y los de SWARFSUR de -20.77 ± 5.04 W m-2 en la estación seca, induciendo una tasa de calentamiento (HR) de 0.37 ± 0.13 K día-1. El presente estudio muestra que, para series largas de medición, los efectos ocasionados por los aerosoles en el flujo radiativo en un bosque virgen de la Amazonia Central fueron del orden de -3.66 ± 1.59 W m-2 para SWARFTOA y de -11.86 ± 2.35 W m-2 para SWARFSUR durante la temporada húmeda.

This work aims to evaluate the possible relations between the confirmed daily cases of COVID-19 and the environmental parameters for the Cuiabá-Várzea Grande conurbation in the state of Mato Grosso, Brazil. The data sets used to cover the rainy-dry periods, from January to December 2020, were achieved from a database of government institutions, and processed through the Spearman correlation test. Our results showed that atmospheric pressure and fire radiative power has a significant positive correlation, suggesting that these parameters favor the transmission of COVID-19. On the other hand, the relative humidity of the air and the total column of water vapor showed a significant negative correlation with the number of confirmed daily cases of COVID-19, which indicates that the water vapor present in the atmosphere acts in the regulation of virus transmission. Thus, taking into account the results obtained, there is a need for collaborative policies and measures among the three spheres of executive power in Brazil, to act in the surveillance of fire cases, which can favor the transmission of COVID-19. In addition, prevention and protection measures aimed at reducing the spread of coronavirus continue to be indispensable.

Resumo As variações das propriedades óticas dos aerossóis podem interferir nos processos de transferência de energia entre a atmosfera e a superfície terrestre. A AOD (Aerosol Optical Depth) é a variável mais usada para este propósito, a qual possibilita obtenção das principais tendências e periodicidades das variações. Este trabalho objetivou verificar a habilidade das técnicas SSA (Singular Spectrum Analysis) e Wavelet em descrever as flutuações, e respectivas periodicidades, presentes em uma série temporal de 12 anos (2003-2014) de AOD na faixa do espectro de 550 nm (AOD 550 nm) sobre a região do Pantanal brasileiro. Os dados de AOD 550 nm foram adquiridos dos produtos do sensor MODIS, a bordo dos satélites TERRA e AQUA, e foram submetidos a análise de SSA, permitindo a descrição das principais periodicidades da AOD 550 nm, além de constatar dois períodos dominantes, 1 e 0,5 ano, tendo pequenas variações. A Wavelet de Morlet inferiu as periodicidades estatisticamente significativas, entre as quais também foram detectadas periodicidades anual e semestral. Ambas as técnicas reproduziram as principais oscilações dos valores da AOD 550 nm, bem como a gradativa redução dos valores de AOD 550 nm a partir de 2011. A Wavelet possibilitou a interpretação e visualização das principais periodicidades ao longo do tempo, sendo possível verificar em quais instantes as periodicidades ocorreram.

Abstract Variations of the optical properties of aerosols can interfere in the energy transfer processes between the atmosphere and the Earth's surface. Aerosol Optical Depth (AOD) has been most used variable to investigate such variations, which enabling the achievement of main trends and periodicities from AOD time series. This study aimed to verify the sensitivity of Singular Spectrum Analysis (SSA) and Wavelet techniques on a time series of 12 years (2003-2014) AOD at wavelengths 550 nm (AOD 550 nm) over the Brazilian Pantanal region. AOD 550 nm data set were acquired from MODIS sensor and were subjected by SSA, allowing description of the main frequencies of the AOD 550 nm and of two dominant periods of 1 and 0.5 year. From Morlet Wavelet model were inferred major statistically significant periodicity, among which were also detected an annual and a biannual frequencies. Both techniques explained the main variations of the values of AOD 550 nm on the area of study, moreover, detected a gradual reduction in AOD 550 nm values from 2011. The Wavelet analysis allowed the interpretation and visualization of the main periodicities over time, being possible to identify at what instant such periodicities series occurred.