Aerosol Optical Depth and Precipitation

The relationship between aerosol optical depth (AOD) and temperature is a complex and significant aspect of climate science, impacting atmospheric dynamics and weather patterns on both regional and global scales. Aerosols, consisting of fine solid or liquid particles suspended in the atmosphere, play a critical role in shaping the Earth’s energy balance and climate system. This review chapter aims to provide a comprehensive analysis and synthesis of existing research on the interactions between aerosol optical depth and temperature, elucidating the underlying mechanisms and regional variations. Key findings from observational studies revealed the diverse effects of aerosols on temperature. Reflective aerosols cool the surface scattering solar radiation while absorbing aerosols, such as black carbon and organic aerosols, warm the atmosphere by absorbing solar energy. The chapter further investigates the influence of aerosol optical depth on cloud formation and precipitation patterns. Moreover, this review emphasizes the regional variability of aerosol effects on temperature and rainfall, emphasizing the significance of local meteorological conditions, aerosol types, and geographical locations. In conclusion, a comprehensive understanding of the relationship between aerosol optical depth and temperature is vital for accurate climate modeling and predictions. The insights gained from this chapter contribute to the knowledge base for climate scientists, policymakers, and researchers, paving the way for targeted strategies to mitigate the impacts of aerosols on climate change and fostering sustainable environmental practices. As climate change remains a pressing global concern, the findings of this chapter offer valuable guidance in addressing the challenges posed by aerosols in the Earth’s atmosphere.

This study delves into the temporal and spatial dynamics of various atmospheric parameters and lightning activity in Uttarakhand, India. Between January and May, there was a notable surge in aerosol optical depth (AOD) attributed to an inflow of aerosols from the Thar Desert and arid regions. AOD peaks in May and subsequently diminishes due to the removal of aerosols from the atmosphere. The month of May exhibits the highest lightning activity, accompanied by noteworthy events in March, April, June, July, August, and September. However, the peak flash rate in May (0.065 flashes/km²/day) is high in comparison to reported values (6.5 flashes/km²/day) over the monsoon zone of India. Convective Available Potential Energy (CAPE) values exhibit an ascending trend from January onwards, reaching their highest values in May, July, and August, driven by rising surface temperatures. Conversely, surface cooling in June leads to a reduction in lightning activity. Lower Outgoing Longwave Radiation (OLR) values observed in June and July suggest the presence of clouds, resulting in substantial rainfall, particularly in Uttarakhand (10975.79 mm and 9640.69 mm). This pattern bears resemblance to findings in the Indian monsoon zone reported previously. Spatially, Uttarakhand experiences distinct seasonal variations in lightning activity, with the lowest in the summer foothills and the highest in the southeastern region from July to September, primarily driven by summer and monsoon convection. Principal component analysis (PCA) reveals robust correlations between flash count, CAPE, and temperature, primarily influenced by land surface heating during the pre-monsoon and monsoon seasons. The flash count also demonstrates a significant positive correlation with AOD, suggesting an impact of aerosols on lightning. OLR shows a negative correlation with flash count in the monsoon zone. Based on seasonal variation, AOD dominance during the pre-monsoon and monsoon seasons, increased lightning activity, reduced OLR values, and a positive correlation between AOD and lightning frequency under clean conditions.

Aerosol-cloud-precipitation interactions in seven non-attainment cities with elevated particulate matter levels is studied. Aerosol mode analysis indicates the dominance of fine particulate matter. AOD levels are notably higher in Delhi, while other cities exhibit AOD levels with no significant trends. Correlations between Precipitation (PRCP) and Cloud Effective Radius (CER) suggest the second indirect effect. A random forest model highlights AOD and Cloud Fraction (CF) as key predictors of PRCP, with meteorological factors dominating Delhi. The study underscores the complexity and spatiotemporal variability of aerosol-cloud-precipitation interactions, necessitating a multifaceted approach for a comprehensive understanding.

“Impact of COVID-19 Lockdowns on Air Quality in East India: A Comparative Analysis of PM2.5 and Black Carbon Emissions during the First and Second Waves of the Pandemic” The COVID-19 pandemic has had a devastating toll on human lives worldwide, leading many countries to implement strict lockdowns and restrictions in an effort to combat the virus. While these measures were crucial for public health, they also had significant implications for the global economy and human well-being. One notable effect of the lockdowns was the reduction in emissions of particulate matter (PM2.5), Black Carbon (BC), aerosols, and other air pollutants in the atmosphere. This decline in human activities during the lockdowns contributed to an improvement in air quality. The pandemic unfolded in two waves: the First Wave (March–June 2020) and the Second Wave (March–June 2021). During both of these periods, we closely monitored the levels of PM2.5, BC, and meteorological parameters in the industrial cities of Sakchi (S1) and Gamharia (S2) in East India. In the First Wave, there was a noticeable drop in PM2.5 mass concentrations at S1 and S2, with levels ranging from 134 to 27 μg m⁻³ and 127 to 34 μg m⁻³, respectively. Similarly, BC mass concentrations showed a decrease, ranging from 56 to 10 μg m⁻³ at S1 and 48.8 to 10 μg m⁻³ at S2. In the Second Wave of COVID-19, we observed a rise in PM2.5 mass concentrations, with levels ranging from 117 to 164 μg m⁻³ at S1 and 123 to 159 μg m⁻³ at S2. The corresponding BC mass concentrations ranged from 23.5 to 66.6 μg m⁻³ at S1 and 23.2 to 71 μg m⁻³ at S2. This comparison indicates that PM2.5 and BC mass concentrations increased from the first to the Second Wave of the pandemic. However, it is worth noting that due to partial lockdowns or shutdowns during the Second Wave, the mass concentrations might still have been lower compared to regular days. Furthermore, the analysis of backward trajectories revealed that aerosol movement experienced a more significant reduction during the First Wave compared to the Second Wave, which had a moderate effect. In terms of health risks associated with BC exposure, the Npsc values ranged from 20.8 to 103.7 for CM, LC, LBW, and PLED during the First Wave and 14.4 to 61.6 during the Second Wave. In conclusion, the COVID-19 lockdowns had a discernible impact on air quality in East India, with reduced emissions of PM2.5 and BC during the First Wave and a partial improvement during the Second Wave. However, it is crucial to consider the complex interactions between human activities, air pollution, and public health when interpreting these findings.

In recent years, polychlorinated biphenyls (PCBs) in the environment gained scientific interest because of their persistent nature, widespread occurrence, and the potential threats they pose to humans and the environment. PCBs are recognized by the International Agency for Research on Cancer (IARC) as Group 1 carcinogens or cancer-causing substances. Although the occurrence and distribution of PCBs in various environmental matrices are reported in recent studies, the distribution and source of PCB pollution in ambient air across the globe still remain unclear. Inhalation exposure to these contaminants is often overlooked because ambient air is contaminated with different forms of PCBs. Exposure to PCBs in ambient air has recently been given unambiguous consideration in the human health risk assessment that form the basis of risk management decisions. The occurrence of high PCB levels, notably in urban and industrial areas, might result from extensive PCB use and intensive human activity. Furthermore, PCB exposure in the outdoor environment may pose a risk for humans through inhalation of contaminated air or ingestion of dust. In such settings, inhalation route may contribute significantly to PCB exposure. The data on human health effects due to PCB inhalation are scarce. Inorder to address this gap, this review discusses the occurrence, distribution, health impact, and various risk assessment techniques of PCBs for environmental and human health.

This chapter covers a comprehensive review of air pollution in the southern part of Iraq. Pollutants released into the atmosphere of various places within the geographic borders of this region included gaseous pollutants of CO, CO₂, NO_x, SO_x, O₃, suspended particles, hydrocarbons (mainly polycyclic aromatic hydrocarbons), and heavy metals. This review showed that the main sources of these pollutants were oil industries, fossil fuel combustion, energy production, dust storms, transportation, industry, and public generators. Data from some studies indicated that these pollutants exceeded the national and international standard criteria. There was an increase in gaseous pollutants such as CO, NO_x, SO_x, and O₃ as a result of the intense use of fossil fuel combustion, industry, transportation, and electrical power generation. The increase of suspended particles in the air was mainly from burning fossil fuels, transportation modes, power generation, industrial activities such as brick manufacturing, and dust suspension by wind and dust storms. High concentrations of polycyclic aromatic hydrocarbons were recorded as a result of oil production and refining in addition to power generation and the bricks industry. An increase in the heavy metals concentration such as Pb, Cr, Cu, Cd, Ni, Co, and Hg may have resulted from industrial activities such as the manufacture of bricks; oil industries; combustion of fossil fuels, power generation, traffic, and tires; and brakes wear. Some studies have indicated that the increase in the prevalence of many diseases, such as respiratory and cardiovascular diseases, together with cancer cases in this region of Iraq, was due to pollutant increase in the atmosphere.

Understanding aerosols is paramount, as an inadequate grasp of their properties and their variations across time and space could lead to irreversible consequences, with the potential for an overwhelming surge in atmospheric particle levels. Within the realm of aerosols, anthropogenic types, encompassing water-soluble aerosols and black carbon, hold sway over the “optical depth,” while natural aerosols, such as mineral dust and sea salt, dominate in terms of aerosol mass concentration. Empirical evidence confirms that black carbon aerosols play a substantial role in regional-scale global warming, contributing over 65% to the annual net atmospheric forcing. Moreover, black carbon aerosols significantly contribute to solar dimming, constituting 50% or more of radiative forcing at the Earth’s surface. The marked surface forcing and atmospheric warming induced by black carbon aerosols may exert a pronounced influence on the hydrological cycle. Tropospheric aerosols wield a substantial impact on the Earth’s climate, spanning local, regional, and global scales. In the atmospheric aerosol spectrum, two distinct categories emerge fine and coarse modes. Coarse mode aerosols, such as wind-borne mineral dust and sea salt particles, predominantly emanate from natural sources, while fine mode aerosols, prevalent over urban, industrialized, and densely populated regions, predominantly result from gas-to-particle conversion mechanisms stemming from activities like fossil fuel and biomass combustion, as well as other anthropogenic sources. The combustion of fossil fuels, particularly coal and biomass, has been identified as the leading contributor to global emissions.

The Innovative Air-Purifying Mask, introduced as a comprehensive solution to combat toxic gas-related health risks, encapsulates a paradigm shift in addressing air quality and respiratory health. Through meticulous integration of advanced filtration technology, natural air-purifying elements, and essential pure molecules, this mask has demonstrated its potential to revolutionise the field of air purification. As we reflect on the journey of exploring this novel solution, we summarise the key findings, emphasise its significance, and call for collective action to address the pressing challenges of environmental health.

This chapter navigates through the intricate web of air pollution, dissecting its impact on human health, particularly on vulnerable populations. It explores the chemistry of toxic gases and their sources, highlighting the need for innovative solutions. The chapter also examines existing air purification methods and their limitations, laying the groundwork for the introduction of the game-changing air-purifying mask.

The core of this chapter lies in the detailed exploration of the mask’s design, materials, and functionality. It delves into the significance of each component, from the charcoal layer that adsorbs harmful gases to the spider leaf layer that harnesses the power of nature in air purification. The HEPA layer, with its exceptional filtration capabilities, takes centre stage in the fight against particulate matter.

As readers journey through this chapter, they will gain a comprehensive understanding of the Innovative Air-Purifying Mask’s potential to safeguard respiratory health. The integration of scientific principles, innovative design, and environmental consciousness embodies a holistic approach to addressing the challenges posed by toxic gases. It is a beacon of hope in the quest for cleaner air and a healthier tomorrow.

Various anthropogenic activities such as fuel combustion, industrial processes, non-industrial fugitive sources, transportation, construction activities, brick kiln, and biomass burning are the main sources of particulate matter in Bangladesh. Previous research reported that yearly PM_2.5 and PM₁₀ concentrations are several times higher than the national standards of Bangladesh. A number of adverse health impacts have been associated with exposure to particulate matter and more than 37,000 Bangladeshi people die every year from diseases related to air pollution. In recent years, the government of Bangladesh has become concerned about controlling aerosol emissions coming from anthropogenic sources. However, only a few studies have been conducted on the variation of aerosol in Bangladesh while manuscripts related to policies controlling particulate matter are very limited with inappropriate implementation.

As a result, the combination of meteorological conditions and local sources results in particulate matter concentrations much higher than the Bangladesh National Ambient Air Quality Standard (BNAAQS). Bangladesh’s government has taken several steps to reduce aerosol emissions by introducing lower sulfur fuel, improving the flexibility of vehicles, and introducing new technology for brick production. Air pollution caused by aerosol particulates not only affects our daily lives but also negatively affects our environment, so we need to come forward together by making efforts personally, socially, and legally. This chapter discusses sources and meteorological factors affecting particulate matter as well as management approaches to mitigate air pollution.

Aerosols are microscopic solid or liquid particles suspended in the air people breathe. Despite their tiny size, aerosols are extremely important to human health and the planet’s climate. Aerosols in the atmosphere come from both manmade and natural sources. Their diameters in the atmosphere range from a few nanometers to micrometers, depending on where they come from and what kind they are. Numerous respiratory viruses can spread through contact and droplet transmission. The World Health Organization (WHO) has warned that the SARS-CoV-2 virus, known as COVID-19, may spread via airborne transmission. According to growing epidemiological evidence, viral aerosol is an important mode of transmission for coronavirus and influenza due to its high infectiousness and propensity for rapid spread. Another crucial topic of study is how bioaerosols contribute to the current COVID-19 pandemic’s transmission. Evidence suggests that, in favorable circumstances, aerosols aid in transmitting COVID-19. When a person with the virus exhales microscopic particles that hang in the air without much dilution, this could result in short-range aerosol transmission. If enough are breathed in by a susceptible person, they could spread the infection. Aerosol particles dispersing away from the diseased person can also expose them. At distances more than a few feet, COVID-19 can be spread by inhaling the virus in the air. An entire room or indoor space can get contaminated with particles from an ill person. According to popular belief, SARS-CoV-2 spreads via droplets released during ill individuals’ coughing, sneezing, talking, or exhaling. Some droplets fall on surrounding floors or surfaces because they are too heavy to stay in the air.

Atmospheric aerosols, composed of suspended particulate matter and aerosol optical depth (AOD), exert a crucial role in regulating air quality. However, existing studies primarily focus on the direct health impacts of aerosols, neglecting the investigation of their indirect effects on fertility, child mortality, maternal health, and domestic environments. Understanding these indirect impacts becomes paramount, particularly in densely populated regions with high aerosol concentrations. This study delves into the association between AOD and key health and malnutritional indicators across Chennai, Coimbatore and Salem districts in Tamil Nadu, India. We conducted an extensive analysis of satellite-derived AOD data (NASA-VIIRS), and nutritional status from National Family Health Survey NFHS-4 (2015–2016) and NFHS-5 (2019–2021) over a 5-year period. Our research uncovers a significant correlation between heightened AOD levels and adverse health outcomes. Furthermore, increased AOD is linked to elevated nutritional status, implying the detrimental effects of air pollution on vulnerable populations. Interestingly, as we delve into the link between AOD and malnutrition rates, focusing particularly on stunting (0.33%), wasting (0.32%), and underweight (0.34%), this analysis uncovers some compelling revelations. These findings underscore the critical importance of considering the indirect impact of AOD on nutritional health of children. By shedding light on the indirect implications of atmospheric aerosols, this research provides essential insights for policymakers and environmental authorities.

The study also aims to understand the aerosol optical depth (AOD) relationship with land and ocean by considering their mapping with Particulate Matter (PM_2.5) for Manali, with Chennai being a coastal area with abundant aerosols for the period 2016–2020. The AOD data is obtained from NASA’s Visible Infrared Imaging Radiometer Suite (VIIRS) Deep Blue Aerosol satellite using its daily datasets. The study is constructed to find the association between AOD and PM_2.5 using machine learning algorithms namely artificial neural network (ANN) and support vector machine (SVM). Furthermore, compare the machine learning techniques with a combination of hybrid algorithms, which is a naturally inspired algorithm; BAT acts together with ANN to get the optimized result. The performance of the models was verified using performance indicator namely RMSE. The prediction efficiency shows that out of two machine learning algorithms and one hybrid algorithm, the hybrid algorithm performed better. Overall, the BAT along with ANN performed better than other models in pattern recognition. The correlation coefficient (R²) of PM_2.5 and AOD is 0.58. Statistical analysis shows that the mean and standard deviation of AOD and PM_2.5 are 55.53 ± 42.11 and 2.89 ± 1.45, respectively, along with their skewness of 3.477 and 0.289, followed by a kurtosis of AOD and PM_2.5 at 328 0.97 and 17.06, respectively. The results showed that 98% and 99% of training and 2% and 1% of ANN tests had better results with RMSE of 21.09 μg/m³, 22.05 μg/m³ during training, and 17.95 μg/m³ and 12.54 μg/m³ provided for testing. For SVM, the normalized poly kernel function was found to be the best out of four functions, with an RMSE of ±21.79 μg/m³ in training and ± 15.7 μg/m³ in testing for 98%,99% of training and 2%,1%of tests. The study concludes that the hybrid algorithm model proves AOD’s ability to make near-term future PM_2.5 predictions.

This chapter investigates the influence of Aerosol Optical Depth (AOD) on monsoon shifts and pollution in the Amaravathi River basin during the monsoon seasons of 2000, 2010, and 2022. The analysis reveals significant correlations between AOD levels and changes in monsoon, leading to alterations in rainfall patterns and seasonal temperatures. Higher AOD concentrations are linked to shifts in the monsoon season, impacting its onset, intensity, and duration, with implications for the region’s ecosystems, agriculture, and water resources. Additionally, the chapter addresses pollution issues caused by urbanization, industrialization, and agriculture, contributing to water quality degradation and adversely affecting aquatic life. The study emphasizes the need to consider AOD levels when formulating climate resilience and pollution control strategies for the Amaravathi River basin, providing valuable insights for sustainable development and environmental management in the area.

Aerosols play a significant role in the Earth’s atmospheric dynamics. Aerosol optical depth (AOD) stands out as the paramount parameter for assessing aerosol loads in the atmosphere, particularly through satellite measurements. AOD is influenced by a complex interplay of meteorological and anthropogenic factors. While these factors are inherently intertwined, the pressing need for clean air is increasingly recognized as an existential crisis.

The surge in AOD can be attributed to various drivers of economic development, including increased energy demand, urbanization, and population growth. Additionally, activities such as biomass burning, industrial emissions, and construction contribute significantly to AOD, with emissions of precursors like NO₂ and SO₂ playing crucial roles. The diversity of aerosol types further complicates the assessment of AOD; each type exerts its own distinct influence on atmospheric dynamics.

Moreover, the size of aerosols also plays a discernible role in their impact. The combination of aerosols and their interaction with atmospheric dynamics adds further complexity. AOD and cloud dynamics are intricately linked, and their combined effects can lead to extreme precipitation events or droughts, influenced by factors such as relative humidity and temperature.

While the implications of rising AOD vary across different landscapes, the imperative to mitigate its effects on climate and health remains paramount. Strategic planning and policies enacted by lawmakers have the potential to mitigate the anthropogenic impact of aerosols and slow down the progression of climate change. This chapter aims to provide insights into the human influence on AOD, including its sources, types, influence on precipitation, and strategies for aerosol mitigation.

The continuous rise in energy demand, the decrease in fossil fuel reserves, and the adverse environmental effects of these fuels have increased the interest in renewable resources all over the world. The use of biomass as an energy source has aroused promising interest on global and national scale, as it can alleviate the pressure on environmental pollution as being a renewable resource. By using sustainable biomass conversion technologies, multiple advantages can be achieved, such as preventing climate change, protecting the environment and human health, and obtaining useful energy and high-value-added products. Combustion is a conventional economical thermal method for energy conversion of biomass. One of the most convenient methods for effectively utilizing biomass resources in heat and electricity generation is to convert these fuels into standardized pellet fuels. However, the combustion of agricultural wastes causes an increase in anthropogenic particulate matter (PM) emissions, which pose a threat to human health and the environment. Especially, ultrafine particulate matter (PM0.1–2.5) emissions have much higher health risks as they can act as a transport vector for pathogens, such as SARS-CoV-2–COVID-19. PM emissions from biomass combustion cannot be ignored and necessitates more research. Alkaline metals in biomass play a key role in the formation of PM emissions. Additives can be used to control pollutant emissions from combustion systems. This chapter covers the combustion of biomass in the presence of additives in order to mitigate total particulate matter emissions and ash-associated problems within small-scale combustion devices.