Search Results (5)

Surface methane (CH₄) is a significant precursor of tropospheric ozone (O₃), a greenhouse gas that detrimentally impacts crops by suppressing their physiological processes, such as photosynthesis. This relationship implies that CH₄ emissions can indirectly harm crops by increasing troposphere O₃ concentrations. While this topic is important, few studies have specifically examined the combined effects of CH₄ and CH₄-induced O₃ on rice yield and production. Utilizing the GEOS-Chem model, we assessed the potential reduction in rice yield and production in Asia against a 50% reduction in anthropogenic CH₄ emissions relative to the 2010 base year. Based on O₃ exposure metrics, the results revealed an average relative yield loss of 9.5% and a rice production loss of 45,121 kilotons (Kt) based on AOT40. Regions such as the India-Gangetic Plain and the Yellow River basin were particularly affected. This study determined that substantial reductions in CH₄ concentrations can prevent significant rice production losses. Specifically, curbing CH₄ emissions in the Beijing-Tianjin-Hebei region could significantly diminish the detrimental effects of O₃ on rice yields in China, Korea, and Japan. In summary, decreasing CH₄ emissions is a viable strategy to mitigate O₃-induced reductions in rice yield and production in Asia. Full article

Methane (CH₄) emanating from terrestrial sources serves as a precursor for the genesis of tropospheric ozone (O₃), a pernicious atmospheric contaminant that adversely modulates the physiological mechanisms of agricultural crops. Despite the acknowledged role of CH₄ in amplifying O₃ concentrations, the extant literature offers limited quantitative evaluations concerning the repercussions of CH₄-mediated O₃ on cereal yields. Employing the GEOS-Chem atmospheric chemistry model, the present investigation elucidates the ramifications of a 50% diminution in anthropogenic CH₄ concentrations on the yield losses of maize, soybean, and wheat across Asia for the fiscal year 2010. The findings unveil pronounced yield detriments attributable to O₃-induced phytotoxicity, with the Indo-Gangetic Plain and the North China Plain manifesting the most substantial yield impairments among the crops examined. A halving of anthropogenic CH₄ effluents could ameliorate considerable losses in cereal production across these agriculturally pivotal regions. CH₄-facilitated O₃ exerts a pernicious influence on cereal yields; nevertheless, targeted mitigation of CH₄ effluents, particularly in the vicinity of the North China Plain, holds the potential to substantially attenuate O₃ contamination, thereby catalyzing an enhancement in regional cereal production. Full article

Information about the energetic electron precipitation (EEP) from the radiation belt into the atmosphere is important for assessing the ozone variability and dynamics of the middle atmosphere during magnetospheric and geomagnetic disturbances. The accurate values of energetic electron fluxes depending on their energy range are one of the most important problems for calculating atmospheric ionization rates, which, in turn, are taken into account for estimating ozone depletion in chemistry–climate models. Despite the importance of these processes for the high latitudes of middle atmosphere, precipitation of energetic electrons is still insufficiently studied. In order to better understand EEP and related processes in the atmosphere, it is important to have many realistic observations of EEP in order to correctly characterize their spectra. Invading the atmosphere, precipitating energetic electrons, in the range from tens of keV to relativistic energies of more than 1 MeV, generate bremsstrahlung, which penetrates into the stratosphere and is recorded by detectors on balloons. However, these observations can be made only when the balloon is at stratospheric heights. Near-Earth satellites, such as the polar-orbiting operational environmental satellites (POES), are constantly registering precipitating electrons in the loss cone, but are moving too fast in space. Based on a comparison of the results of EEP measurements on balloons and onboard POES satellites in 2003, we propose a criterion that makes it possible to constantly monitor EEP ionization at stratospheric heights using observations on POES satellites. Full article

Dynamical processes and changes in the ozone layer in the Arctic stratosphere during the winter of 2019–2020 were analyzed using numerical experiments with a chemistry-transport model (CTM) and reanalysis data. The results of numerical calculations using CTM with Dynamic parameters specified from the Modern Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) reanalysis data, carried out according to several scenarios of accounting for the chemical destruction of ozone, demonstrated that both Dynamic and chemical processes contribute significantly to ozone changes over the selected World Ozone and Ultraviolet Radiation Data Centre network stations, both in the Eastern and in the Western hemispheres. Based on numerical experiments with the CTM, the specific Dynamic conditions of winter–spring 2019–2020 described a decrease in ozone up to 100 Dobson Units (DU) in the Eastern Hemisphere and over 150 DU in the Western Hemisphere. In this case, the photochemical destruction of ozone in both the Western and Eastern Hemispheres at a maximum was about 50 DU with peaks in April in the Eastern Hemisphere and in March and April in the Western Hemisphere. Heterogeneous activation of halogen gases on the surface of polar stratospheric clouds, on the one hand, led to a sharp increase in the destruction of ozone in chlorine and bromine catalytic cycles, and, on the other hand, decreased its destruction in nitrogen catalytic cycles. Analysis of wave activity using 3D Plumb fluxes showed that the enhancement of upward wave activity propagation in the middle of March over the Gulf of Alaska was observed during the development stage of the minor sudden stratospheric warming (SSW) event that led to displacement of the stratospheric polar vortex to the north of Canada and decrease of polar stratospheric clouds’ volume. Full article

The chemistry of the nitrate radical and its contribution to organo-nitrate formation in the troposphere has been investigated using a mesoscale 3-D chemistry and transport model, WRF-Chem-CRI. The model-measurement comparisons of NO₂, ozone and night-time N₂O₅ mixing ratios show good agreement supporting the model’s ability to represent nitrate (NO₃) chemistry reasonably. Thirty-nine organo-nitrates in the model are formed exclusively either from the reaction of RO₂ with NO or by the reaction of NO₃ with alkenes. Temporal analysis highlighted a significant contribution of NO₃-derived organo-nitrates, even during daylight hours. Night-time NO₃-derived organo-nitrates were found to be 3-fold higher than that in the daytime. The reactivity of daytime NO₃ could be more competitive than previously thought, with losses due to reaction with VOCs (and subsequent organo-nitrate formation) likely to be just as important as photolysis. This has highlighted the significance of NO₃ in daytime organo-nitrate formation, with potential implications for air quality, climate and human health. Estimated atmospheric lifetimes of organo-nitrates showed that the organo-nitrates act as NO_x reservoirs, with particularly short-lived species impacting on air quality as contributors to downwind ozone formation. Full article