Attenuation of ultraviolet radiation reaching the surface due to atmospheric aerosols in Guangzhou

Relation of pandemics with solar cycles through ozone, cloud seeds, and vitamin D

The global records of infectious diseases, including Western and Eastern documents from 1825 to 2020, during which sunspot observations are considered reliable, show that 27 of the 34 pandemic outbreaks were coincident with sunspot number maxima or minima. There is evidence that the intensity of galactic cosmic rays is anti-correlated with solar activity and that cloud seed formation is accelerated by galactic cosmic rays. There are a substantial number of research papers showing the relationship between COVID-19 and vitamin D deficiency. The data analysis of ozone thickness measured based on NASA satellite observations revealed that ozone thickness has 11-year and 28-month cycles. Because the 11-year cycles of ozone thickness and cloud seed attenuation are anti-correlated, when either one becomes extremely thick, such as at the maximum or minimum point of solar activity, UV radiation is over-attenuated, and human vitamin D deficiency is globally increased. This finding explains the coincidence of pandemic outbreaks with the extrema of the sunspot numbers. Vitamin D supplementation can be an effective countermeasure against the spread of infectious diseases, which is a paramount importance to global society. Future pandemic forecasting should include the 11-year and 28-month cycles of UV radiation. This founding completes the relationship between solar activity and human health through the earth's environment.

The pathway of impacts of aerosol direct effects on secondary inorganic aerosol formation

Airborne aerosols reduce surface solar radiation through light scattering and absorption (aerosol direct effects, ADEs), influence regional meteorology, and further affect atmospheric chemical reactions and aerosol concentrations. The inhibition of turbulence and the strengthened atmospheric stability induced by ADEs increases surface primary aerosol concentration, but the pathway of ADE impacts on secondary aerosol is still unclear. In this study, the online coupled meteorological and chemistry model (WRF-CMAQ; Weather Research and Forecasting-Community Multiscale Air Quality) with integrated process analysis was applied to explore how ADEs affect secondary aerosol formation through changes in atmospheric dynamics and photolysis processes. The meteorological condition and air quality in the Jing-Jin-Ji area (denoted JJJ, including Beijing, Tianjin, and Hebei Province in China) in January and July 2013 were simulated to represent winter and summer conditions, respectively. Our results show that ADEs through the photolysis pathway inhibit sulfate formation during winter in the JJJ region and promote sulfate formation in July. The differences are attributed to the alteration of effective actinic flux affected by single-scattering albedo (SSA). ADEs through the dynamics pathway act as an equally or even more important route compared with the photolysis pathway in affecting secondary aerosol concentration in both summer and winter. ADEs through dynamics traps formed sulfate within the planetary boundary layer (PBL) which increases sulfate concentration in winter. Meanwhile, the impact of ADEs through dynamics is mainly reflected in the increase of gaseous-precursor concentrations within the PBL which enhances secondary aerosol formation in summer. For nitrate, reduced upward transport of precursors restrains the formation at high altitude and eventually lowers the nitrate concentration within the PBL in winter, while such weakened vertical transport of precursors increases nitrate concentration within the PBL in summer, since nitrate is mainly formed near the surface ground.

UV Index Forecasting under the Influence of Desert Dust: Evaluation against Surface and Satellite-Retrieved Data

Human exposure to healthy doses of UV radiation is required for vitamin D synthesis, but exposure to excessive UV irradiance leads to several harmful impacts ranging from premature wrinkles to dangerous skin cancer. However, for countries located in the global dust belt, accurate estimation of the UV irradiance is challenging due to a strong impact of desert dust on incoming solar radiation. In this work, a UV Index forecasting capability is presented, specifically developed for dust-rich environments, that combines the use of ground-based measurements of broadband irradiances UVA (320–400 nm) and UVB (280–315 nm), NASA OMI Aura satellite-retrieved data and the meteorology-chemistry mesoscale model WRF-Chem. The forecasting ability of the model is evaluated for clear sky days as well as during the influence of dust storms in Doha, Qatar. The contribution of UV radiation to the total incoming global horizontal irradiance (GHI) ranges between 5% and 7% for UVA and 0.1% and 0.22% for UVB. The UVI forecasting performance of the model is quite encouraging with an absolute average error of less than 6% and a correlation coefficient of 0.93. In agreement with observations, the model predicts that the UV Index at local noontime can drop from 10–11 on clear sky days to approximately 6–7 during typical dusty conditions in the Arabian Peninsula—an effect similar to the presence of extensive cloud cover.

Impact of typhoon periphery on high ozone and high aerosol pollution in the Pearl River Delta region

This paper analyzes observation data in the Pearl River Delta (PRD) region from 2012 to 2013, and explores the impact of typhoon periphery on high ozone and high aerosol pollution episodes (double high episodes). Observation analysis show that severe tropical storms to severe typhoons are mainly located in the range of 10°N-30°N, 116°E-135°E when double high episodes occur. Meanwhile, obvious high temperature, low humidity, low wind speed, high actinic flux, high aerosol optical depth (AOD), and high single scattering albedo (SSA) can be observed in double high episodes. The diurnal cycle of the PM_2.5 is significant in double high episodes, and the average peak concentration in the afternoon can exceed 90 μg/m³. The diurnal cycle of PM_2.5 in non-double high episodes is not significant, and the average value is about 34-39 μg/m³. The ozone peak concentration in double high episodes is 81-103 ppbv, which is about 27-40 ppbv higher than that of non-double high episodes. High correlation can be found between the aerosol and ozone diurnal cycles in double high episodes, and r² reaches 0.76. In double high episodes, black carbon, nitrate, and sea salt decrease while sulfate, ammonium, secondary organic carbon, and total PM_2.5 significantly increase in the afternoon. The growth of PM_2.5 in double high episodes is mainly contributed by scattered fine particles from photochemical processes and transmission. The mechanisms that control the double high episodes in the PRD are described below. Ozone and aerosol begin to accumulate under unfavorable meteorological conditions. Via local photochemical processes and external transport, the scattered aerosol increases and leads to an increase in multiple scattering and actinic radiation, which is in turn more favorable for photochemical reaction and further increases the ozone concentration. Meanwhile, high oxidizability promotes the formation of scattered aerosol, creating positive feedback. In addition, the scattered aerosol increases backscattering, which increases the photolysis rate and ozone concentration in the middle and upper boundary layer. Meanwhile, downdraft and turbulence transports high-concentration ozone to the ground.

Role of Nitrogen Dioxide in the Production of Sulfate during Chinese Haze-Aerosol Episodes

Haze events in China megacities involve the rapid oxidation of SO₂ to sulfate aerosol. Given the weak photochemistry that takes place in these optically thick hazes, it has been hypothesized that SO₂ is mostly oxidized by NO₂ emissions in the bulk of pH > 5.5 aerosols. Because NO₂(g) dissolution in water is very slow and aerosols are more acidic, we decided to test such a hypothesis. Herein, we report that > 95% of NO₂(g) disproportionates [2NO₂(g) + H₂O(l) = H⁺ + NO₃^-(aq) + HONO (R1)] upon hitting the surface of NaHSO₃ aqueous microjets for < 50 μs, thereby giving rise to strong NO₃^- ( m/ z 62) signals detected by online electrospray mass spectrometry, rather than oxidizing HSO₃^- ( m/ z 81) to HSO₄^- ( m/ z 97) in the relevant pH 3-6 range. Because NO₂(g) will be consumed via R1 on the surface of typical aerosols, the oxidation of S(IV) may in fact be driven by the HONO/NO₂^- generated therein. S(IV) heterogeneous oxidation rates are expected to primarily depend on the surface density and liquid water content of the aerosol, which are enhanced by fine aerosol and high humidity. Whether aerosol acidity affects the oxidation of S(IV) by HONO/NO₂^- remains to be elucidated.

Aerosol and boundary-layer interactions and impact on air quality

Air quality is concerned with pollutants in both the gas phase and solid or liquid phases. The latter are referred to as aerosols, which are multifaceted agents affecting air quality, weather and climate through many mechanisms. Unlike gas pollutants, aerosols interact strongly with meteorological variables with the strongest interactions taking place in the planetary boundary layer (PBL). The PBL hosting the bulk of aerosols in the lower atmosphere is affected by aerosol radiative effects. Both aerosol scattering and absorption reduce the amount of solar radiation reaching the ground and thus reduce the sensible heat fluxes that drive the diurnal evolution of the PBL. Moreover, aerosols can increase atmospheric stability by inducing a temperature inversion as a result of both scattering and absorption of solar radiation, which suppresses dispersion of pollutants and leads to further increases in aerosol concentration in the lower PBL. Such positive feedback is especially strong during severe pollution events. Knowledge of the PBL is thus crucial for understanding the interactions between air pollution and meteorology. A key question is how the diurnal evolution of the PBL interacts with aerosols, especially in vertical directions, and affects air quality. We review the major advances in aerosol measurements, PBL processes and their interactions with each other through complex feedback mechanisms, and highlight the priorities for future studies.