• Energy Research

In January 2013, a severe regional haze occurred over the North China Plain. An online-coupled meteorology-chemistry model was employed to simulate the impacts of aerosol–meteorology interactions on fine particles (PM _2.5 ) pollution during this haze episode. The response of PM _2.5 to meteorology change constituted a feedback loop whereby planetary boundary layer (PBL) dynamics amplified the initial perturbation of PM _2.5 . High PM _2.5 concentrations caused a decrease of surface solar radiation. The maximal decrease in daily average solar radiation reached 53% in Beijing, thereby leading to a more stable PBL. The peak PBL height in Beijing decreased from 690 m to 590 m when the aerosol extinction was considered. Enhanced PBL stability suppressed the dispersion of air pollutants, and resulted in higher PM _2.5 concentrations. The maximal increase of PM _2.5 concentrations reached 140 μ g m ^−3 in Beijing. During most PM _2.5 episodes, primary and secondary particles increased simultaneously. These results imply that the aerosol–radiation interactions played an important role in the haze episode in January 2013.

AbstractBiomass burning (BB) as an important atmospheric carbon source has significant environmental and climatic influence. The frequent extreme BB cases in recent years have raised extensive concerns, yet the latest changes in BB emission on a global scale are not fully understood. Here, we systematically quantify the changes in BB carbon emission for 1999–2022 by fire types and on different scales based on the Global Fire Emissions Database with small fires (GFED4s) dataset. We find contrasting trends of savanna and boreal forest fires persistent over the study period, shaping the variation of global total BB carbon emission. The receding savanna fire drives a declining global BB carbon emission at −8 Tg C year−1 (−0.4% year−1) for 1999–2022, while an upturn of global carbon emission (5 Tg C year−1, 0.3% year−1) occurs in the recent decadal period (2008–2022) due to intensified boreal forest fires. The burned area decouples from carbon emission in terms of the changing tendency, as exhibited by the decreasing global burned area after 2008. Regionally, the fire carbon emission enhancement over the past 15 years (2008–2022) mainly comes from the boreal forests in northwestern North America, northeastern Siberia, and parts of the savanna area, all of which coincide with local climate change toward higher fire proneness. This study reveals a climate‐driven aggravation of the BB carbon emission, especially in high‐latitude boreal forests, and calls for attention to its potential impacts and effective fire management strategies.

Biomass burning (BB) is a significant air pollution source, with global, regional and local impacts on air quality, public health and climate. Worldwide an extensive range of studies has been conducted on almost all the aspects of BB, including its specific types, on quantification of emissions and on assessing its various impacts. China is one of the countries where the significance of BB has been recognized, and a lot of research efforts devoted to investigate it, however, so far no systematic reviews were conducted to synthesize the information which has been emerging. Therefore the aim of this work was to comprehensively review most of the studies published on this topic in China, including literature concerning field measurements, laboratory studies and the impacts of BB indoors and outdoors in China. In addition, this review provides insights into the role of wildfire and anthropogenic BB on air quality and health globally. Further, we attempted to provide a basis for formulation of policies and regulations by policy makers in China.

La détermination du flux de flottabilité et de sa contribution à l'énergie cinétique de turbulence (TKE) est un problème fondamental dans la couche limite planétaire (PBL). Cependant, en raison de la complexité de la turbulence, les études précédentes ont principalement adopté l'analyse dimensionnelle et la formule empirique pour déterminer le budget TKE. Cette étude introduit le concept de modèle de moteur thermique endoréversible à l'analyse TKE de la couche limite convective (CBL) et établit un modèle théorique basé sur les premiers principes. Nous avons constaté que la contribution totale de la flottabilité à TKE et à l'efficacité du moteur thermique dans la couche limite augmente linéairement avec la hauteur de la couche limite. Le flux de flottabilité dérivé de notre modèle théorique est cohérent avec les résultats de la simulation numérique et de l'analyse dimensionnelle. Cette théorie basée sur le moteur thermique révèle le mécanisme physique de la puissance de TKE générée par la flottabilité. Notre modèle théorique peut remplacer la valeur empirique et fournir une méthode idéale pour la détermination du flux de flottabilité dans PBL. La determinación del flujo de flotabilidad y su contribución a la energía cinética de turbulencia (TKE) es un problema fundamental en la capa límite planetaria (PBL). Sin embargo, debido a la complejidad de la turbulencia, estudios previos adoptaron principalmente el análisis dimensional y la fórmula empírica para determinar el presupuesto de TKE. Este estudio introduce el concepto de modelo de motor térmico endorreversible al análisis de TKE de la capa límite convectiva (CBL) y establece un modelo teórico basado en los primeros principios. Encontramos que la contribución total de la flotabilidad a TKE y la eficiencia del motor térmico en la capa límite aumentan linealmente con la altura de la capa límite. El flujo de flotabilidad derivado de nuestro modelo teórico es consistente con los resultados de la simulación numérica y el análisis dimensional. Esta teoría basada en el motor térmico revela el mecanismo físico de la potencia de TKE generada por la flotabilidad. Nuestro modelo teórico puede reemplazar el valor empírico y proporcionar un método ideal para la determinación del flujo de flotabilidad en PBL. The determination of buoyancy flux and its contribution to turbulence kinetic energy (TKE) is a fundamental problem in planetary boundary layer (PBL).However, due to the complexity of turbulence, previous studies mainly adopted dimensional analysis and empirical formula to determine TKE budget.This study introduces the endoreversible heat engine model concept to the convective boundary layer (CBL) TKE analysis and establishes a theoretical model based on the first principles.We found that the total contribution of buoyancy to TKE and heat engine efficiency in the boundary layer increase linearly with the boundary layer height.The derived buoyancy flux from our theoretical model is consistent with the results from numerical simulation and dimensional analysis.This heat engine-based theory reveals the physical mechanism of the power of TKE generated by buoyancy.Our theoretical model can replace the empirical value and provide an ideal method for buoyancy flux determination in PBL. يعد تحديد تدفق الطفو ومساهمته في الطاقة الحركية للاضطراب (TKE) مشكلة أساسية في طبقة الحدود الكوكبية (PBL). ومع ذلك، نظرًا لتعقيد الاضطراب، اعتمدت الدراسات السابقة بشكل أساسي تحليل الأبعاد والصيغة التجريبية لتحديد ميزانية TKE. تقدم هذه الدراسة مفهوم نموذج المحرك الحراري القابل للانعكاس إلى تحليل TKE للطبقة الحدودية للحمل الحراري (CBL) وتؤسس نموذجًا نظريًا يعتمد على المبادئ الأولى. وجدنا أن المساهمة الإجمالية للطفو في TKE وكفاءة المحرك الحراري في الطبقة الحدودية تزيد خطيًا مع ارتفاع الطبقة الحدودية. يتوافق تدفق الطفو المشتق من نموذجنا النظري مع نتائج المحاكاة العددية وتحليل الأبعاد. تكشف هذه النظرية القائمة على المحرك الحراري عن الآلية الفيزيائية لقوة TKE الناتجة عن الطفو. يمكن للنموذج النظري الخاص بنا أن يحل محل القيمة التجريبية ويوفر طريقة مثالية لتحديد الطفو في PBL.

Abstract. Atmospheric new particle formation (NPF) is an important phenomenon in terms of global particle number concentrations. Here we investigated the frequency of NPF, formation rates of 10 nm particles, and growth rates in the size range of 10–25 nm using at least 1 year of aerosol number size-distribution observations at 36 different locations around the world. The majority of these measurement sites are in the Northern Hemisphere. We found that the NPF frequency has a strong seasonal variability. At the measurement sites analyzed in this study, NPF occurs most frequently in March–May (on about 30 % of the days) and least frequently in December–February (about 10 % of the days). The median formation rate of 10 nm particles varies by about 3 orders of magnitude (0.01–10 cm−3 s−1) and the growth rate by about an order of magnitude (1–10 nm h−1). The smallest values of both formation and growth rates were observed at polar sites and the largest ones in urban environments or anthropogenically influenced rural sites. The correlation between the NPF event frequency and the particle formation and growth rate was at best moderate among the different measurement sites, as well as among the sites belonging to a certain environmental regime. For a better understanding of atmospheric NPF and its regional importance, we would need more observational data from different urban areas in practically all parts of the world, from additional remote and rural locations in North America, Asia, and most of the Southern Hemisphere (especially Australia), from polar areas, and from at least a few locations over the oceans.

AbstractRecent evidence shows that carbon emissions in China are likely to peak ahead of 2030. However, the social and economic impacts of such an early carbon peak have rarely been assessed. Here we focus on the economic costs and health benefits of different carbon mitigation pathways, considering both possible socio-economic futures and varying ambitions of climate policies. We find that an early peak before 2030 in line with the 1.5 °C target could avoid ~118,000 and ~614,000 PM2.5 attributable deaths under the Shared Socioeconomic Pathway 1, in 2030 and 2050, respectively. Under the 2 °C target, carbon mitigation costs could be more than offset by health co-benefits in 2050, bringing a net benefit of $393–$3,017 billion (in 2017 USD value). This study not only provides insight into potential health benefits of an early peak in China, but also suggests that similar benefits may result from more ambitious climate targets in other countries.