Fine particulate matter (PM
, aerodynamic diameter ≤2.5 µm) impacts the climate, reduces visibility and severely influences human health. The Indo-Gangetic Plain (IGP), home to about one-seventh of ...the world's total population and a hotspot of aerosol loading, observes strong enhancements in the PM
concentrations towards winter. We performed high-resolution (12 km × 12 km) atmospheric chemical transport modeling (WRF-Chem) for the post-monsoon to winter transition to unravel the underlying dynamics and influences of regional emissions over the region. Model, capturing the observed variations to an extent, reveals that the spatial distribution of PM
having patches of enhanced concentrations (≥100 µgm
) during post-monsoon, evolves dramatically into a widespread enhancement across the IGP region during winter. A sensitivity simulation, supported by satellite observations of fires, shows that biomass-burning emissions over the northwest IGP play a crucial role during post-monsoon. Whereas, in contrast, towards winter, a large-scale decline in the air temperature, significantly shallower atmospheric boundary layer, and weaker winds lead to stagnant conditions (ventilation coefficient lower by a factor of ~4) thereby confining the anthropogenic influences closer to the surface. Such changes in the controlling processes from post-monsoon to winter transition profoundly affect the composition of the fine aerosols over the IGP region. The study highlights the need to critically consider the distinct meteorological processes of west-to-east IGP and changes in dominant sources from post-monsoon to winter in the formulation of future pollution mitigation policies.
Cities in the global south face dire climate impacts. It is in socioeconomically marginalized urban communities of the global south that the effects of climate change are felt most deeply. Santiago ...de Chile, a major mid-latitude Andean city of 7.7 million inhabitants, is already undergoing the so-called "climate penalty" as rising temperatures worsen the effects of endemic ground-level ozone pollution. As many cities in the global south, Santiago is highly segregated along socioeconomic lines, which offers an opportunity for studying the effects of concurrent heatwaves and ozone episodes on distinct zones of affluence and deprivation. Here, we combine existing datasets of social indicators and climate-sensitive health risks with weather and air quality observations to study the response to compound heat-ozone extremes of different socioeconomic strata. Attributable to spatial variations in the ground-level ozone burden (heavier for wealthy communities), we found that the mortality response to extreme heat (and the associated further ozone pollution) is stronger in affluent dwellers, regardless of comorbidities and lack of access to health care affecting disadvantaged population. These unexpected findings underline the need of a site-specific hazard assessment and a community-based risk management.
Fungal spores play important role in the health of humans, animals, and plants by constituting a class of the primary biological aerosol particles (PBAPs). Additionally, these could mediate the ...hydrological cycle by acting as nuclei for ice and cloud formation (IN and CCN respectively). Various processes in the biosphere and the variations in the meteorological conditions control the releasing mechanism of spores through active wet and dry discharge. In the present paper, we simulate the concentration of fungal spores over the Indian region during three distinct meteorological seasons by combining a numerical model (WRF-Chem) with the fungal spore emissions based on land-use type. Maiden high-resolution regional simulations revealed large spatial gradient and strong seasonal dependence in the concentration of fungal spores over the Indian region. The fungal spore concentrations are found to be the highest during winter (0–70 μg m−3 in December), moderately higher during summer (0–35 μg m−3 in May) and lowest during the monsoon (0–25 μg m−3 in July). The elevated concentrations during winter are attributed to the shallower boundary layer trapping the emitted fungal spores in smaller volume. In contrast, the deeper boundary layer mixing in May and stronger monsoonal-convection in July distribute the fungal spores throughout the lower troposphere (∼5 km). We suggest that the higher fungal spore concentrations during winter could have potential health impacts. While, stronger vertical mixing could enable fungal spores to influence the cloud formation during summer and monsoon. Our study provides the first information about the distribution and seasonal variation of fungal spores over the densely populated and observationally sparse Indian region.
•Fungal spore emissions based on high resolution land use data.•Simulating fungal spore concentration for Indian region.•Role of meteorology/seasons in fungal spore variability.•Need for bioaerosol measurements over Indian region.
The spatial distribution of trace gases exhibit large spatial heterogeneity over the Indian region with an elevated pollution loading over densely populated Gangetic Plains (IGP). The contending role ...and importance of anthropogenic emissions and meteorology in deciding the trace gases level and distribution over Indian region, however, is poorly investigated. In this paper, we use an online regional chemistry transport model (WRF/Chem) to simulate the spatial distribution of trace gases over Indian region during one representative month of only three meteorological seasons namely winter, spring/summer and monsoon. The base simulation, using anthropogenic emissions from SEAC
4
RS inventory, is used to simulate the general meteorological conditions and the realistic spatial distribution of trace gases. A sensitivity simulation is conducted after removing the spatial heterogeneity in the anthropogenic emissions, i.e., with spatially uniform emissions to decouple the role of anthropogenic emissions and meteorology and their role in controlling the distribution of trace gases over India. The concentration levels of Ozone, CO, SO
2
and NO
2
were found to be lower over IGP when the emissions are uniform over India. A comparison of the base run with the sensitivity run highlights that meteorology plays a dominant role in controlling the spatial distribution of relatively longer-lived species like CO and secondary species like Ozone while short-lived species like NO
X
and SO
2
are predominantly controlled by the spatial variability in anthropogenic emissions over the Indian region.
Outdoor air pollution kills more than 4 million people around the world per year and heavy pollution episodes continue to occur especially around large urban centres. In addition to long-term ...mitigation strategies, short-term emission controls are needed to prevent heavy pollution episodes in megacities such as Beijing. Such controls have been implemented with reasonable success in the past, notably during mega-events, but need to be carefully evaluated to develop a robust mitigation strategy for future. In this work, the 10-day long controls implemented before the APEC summit in Beijing during November 2014 were evaluated for their eectiveness using an online atmospheric chemical transport model WRF-Chem. The controls were found to be only partly responsible for the improvement in air quality during the summit period, while the rest of the improvement was due to favourable meteorology which reduced pollutant levels signicantly as compared to the levels before the control period. The controls were found to be insucient in meeting national air quality standards if applied during periods with more stagnant conditions.Sensitivity studies were performed to identify temporally-resolved source contributions from various sectors and regions. It was found that controls on local emissions benet air quality on the same day, controls on regional emissions show peak benets a day or two after the start of controls and controls on distant emissions show peak benets three to four days later. Local and regional residential and industry sectors were found to dominate contributions to PM2.5 levels in Beijing. A Gaussian statistical technique was used to replace the model behaviour over Beijing with a fast emulator to generate concentration response surfaces for emission reductions across various sectors and regions. These results were utilized to develop an optimal policy for short-term emission controls in Beijing and were implemented in an automatic air quality forecasting and emission prescription system which runs the model successively with reduced emissions to meet daily air quality targets and outputs the magnitude and timing of controls needed across various sectors and regions to prevent heavy pollution episodes in Beijing. This is a novel application of the popular method called Model Predictive Control often used in the petrochemical industry, to air quality modelling. The framework developed here is for Beijing but can be readily adopted for any other polluted region of the world.
This study, performed under the umbrella of the Task Force on Hemispheric Transport of Air Pollution (TF-HTAP), responds to the global and regional atmospheric modelling community's need of a mosaic ...emission inventory of air pollutants that conforms to specific requirements: global coverage, long time series, spatially distributed emissions with high time resolution, and a high sectoral resolution. The mosaic approach of integrating official regional emission inventories based on locally reported data, with a global inventory based on a globally consistent methodology, allows modellers to perform simulations of high scientific quality while also ensuring that the results remain relevant to policymakers.
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