A significant proportion of the solar irradiance that reaches the Earth's surface is normally attenuated by atmospheric properties and overcast conditions related to the rainy season. The Solar Analyst (SA) model, irradiance and long term precipitation data were used to assess this relationship in Guadalajara, Mexico. A spatial analysis based on morphological and statistical criteria increased the model's certainty. The SA model explains 95.4% of the irradiation variability observed on the ground, with average uncertainties of 3.7% during clear sky conditions in the dry season and 4.4% on sunny days in the wet season. The meteorological data analysis shows that total precipitation in 2014 had an atypical temporal distribution and was slightly lower (12.6%) than the average from 1991 to 2012. A deficit of 39% in precipitation compared to the long term average was found in the first half of the season, which was later partially compensated. This deficit was interpreted as a temporary delay in high values of precipitation. Based on the potential average irradiation from the SA model and field observations, it can be concluded that overcast conditions related to rainfall through 2014 attenuated approximately 28.5% of the incoming solar energy. Taking the global energy balance into account, this fraction was higher in comparison to the energy proportion reflected by the cloud's albedo (ca 23%). These results suggest that both the high proportion of energy attenuated and atypical weather conditions may be local effects of large‐scale phenomena such as the El Niño‐Southern Oscillation.

Nitrogen dioxide (NO₂) is a critical air pollutant that has significant health and environmental impacts. Tropospheric NO₂ refers specifically to the vertical column density of NO₂, which is measured by satellites and serves as an indicator of anthropogenic NO₂ sources. This pollutant is frequently assessed using satellite data owing to limitations in local monitoring. This investigation employs the Spectral Angle Mapper (SAM), a geometric machine-learning model, given its advantages in simplicity and computational efficiency, and OMI satellite measurements to carry out spatially supervised classification of tropospheric NO₂ global patterns from 2005 to 2021. This study identifies four typical trends across developed urban centers, examining correlations with population growth, economic factors, and air quality policies. The results demonstrated regional variations, with a general downward trend in North America, Europe, and parts of Asia, underscoring the efficacy of stricter emission controls. However, upward trends persist in some Asian regions, reflecting varying policy implementations. This study revealed a pivotal inflection point around 2013, marking a shift in global NO₂ dynamics. Although policies have led to improved air quality in some regions, achieving absolute decoupling of economic growth from NO₂ emissions remains challenging. The COVID-19 pandemic has also exerted a significant influence, temporarily reducing emissions due to economic slowdowns. Overall, the SAM model effectively delineated NO₂ patterns and provided insights for future policy and emission control strategies.

Polycyclic aromatic hydrocarbons (PAHs) and quinones in the gas phase and as submicron particles raise concerns due to their potentially carcinogenic and mutagenic properties. The majority of existing studies have investigated the formation of quinones, but it is also important to consider both the primary and secondary sources to estimate their contributions. The objectives of this study were to characterize PAHs and quinones in the gas and particulate matter (PM₁) phases in order to identify phase distributions, sources, and cancer risk at two urban monitoring sites in the Guadalajara Metropolitan Area (GMA) in Mexico. The simultaneous gas and PM₁ phases samples were analyzed using a gas chromatography–mass spectrometer. The lifetime lung cancer risk (LCR) due to PAH exposure was calculated to be 1.7 × 10⁻³, higher than the recommended risk value of 10⁻⁶, indicating a potential health hazard. Correlations between parent PAHs, criteria pollutants, and meteorological parameters suggest that primary sources are the main contributors to the Σ₈ Quinones concentrations in PM₁, while the secondary formation of 5,12-naphthacenequinone and 9,10-anthraquinone may contribute less to the observed concentration of quinones. Additionally, naphthalene, acenaphthene, fluorene, phenanthrene, and anthracene in PM₁, suggest photochemical degradation into unidentified species. Further research is needed to determine how these compounds are formed.

Tropospheric ozone is an obligatorily-regulated pollutant, to ensure health protection and better air quality. Most countries have established maximum permissible limits (MPL) equal to 0.06 or 0.070 ppmv, but these could be insufficient considering the strictest MPL of the World Health Organization (WHO) guidelines. Such concentrations may still cause health damage to some groups of the population in urban areas. Additionally, the mean value is the principal statistical parameter for monitoring air pollution. This factor may be hiding critical ozone concentrations for public health. This work examines the mean and maximum ozone based on a multi-temporal analysis, to explore the use of a maximum average value as an air quality standard. The mean ozone had a remarkably stationary contrast; while, the maximum ozone emphasized a semi-permanent state of high pollution over the year. Diurnal variation highlights the differences of frequency between the mean and maximum ozone above any MPL, which is accentuated when compared with the WHO guidelines. Under the WHO-MPL, the mean ozone underestimates the highest concentrations; while the maximum ozone represents the extremely high concentrations observed over the year. Instead, the maximum average ozone becomes moderate; this preserves the proper, but conservative high concentrations, following similar temporal patterns as the mean ozone. This parameter is proposed to be adapted as an alternative statistical criterion to prevent negative effects on public health due to high and frequent ozone concentrations in subsequent years.