Drop In Ozone Research Articles

Impact of a gravity wave process on the upper stratospheric ozone valley on the Qinghai-Tibetan Plateau

Atmospheric gravity waves are essential meso-small-scale oscillations that facilitate material exchange within the atmosphere. These waves can significantly affect the ozone layer in the Upper Troposphere and Lower Stratosphere (UTLS) on the Qinghai-Tibetan Plateau. However, the influence of gravity wave dynamic processes on upper stratospheric ozone has rarely been studied. This paper identifies the gravity waves on the Tibetan Plateau based on ECMWF Reanalysis 5 (ERA5) data, analyzes the response of the upper stratospheric ozone to the event, and simulates the dynamic propagation mechanism of gravity waves by the Weather Research and Forecasting (WRF) model. This analysis reveals that between 15:00 and 21:00 UTC on July 29, 2015, gravity waves propagated from the surface of Tibetan Plateau (450 hPa) up to the upper stratosphere (20 − 3 hPa) in an arc-shaped structure and tilted to the east with height. The gravity wave signals started to weaken at 21:00 UTC on the same day. Influenced by the easterly rapids, gravity waves partially broke near 3 hPa at 02:30 UTC on July 30, but gravity wave signals were still present, and gravity waves completely broke and released energy at 04:00 UTC. During this process, ozone in the 20–3 hPa region (upper stratosphere) on the Qinghai-Tibetan Plateau responds well to gravity waves, and the ozone mixing ratio began to drop in ozone concentration 30 min after the partial breakup (03:00 UTC). The ozone dropped drastically by about 0.014 ppmv from 04:00 to 05:00 UTC. The WRF simulation results agree well with ERA5 and accurately capture the intricate characteristics of gravity waves. Furthermore, the breakup of gravity waves caused a total drop in ozone of 0.024 ppmv.

The Long-Term Trends and Interannual Variability in Surface Ozone Levels in Beijing from 1995 to 2020

Tropospheric ozone is an important atmospheric pollutant as well as an efficient greenhouse gas. Beijing is one of the cities with the most serious ozone pollution. However, long-term date of observed ozone in Beijing are limited. In this paper, we combine the measurements of the In-service Aircraft for a Global Observing System (IAGOS), ozonesonde observations as well as the recently available ozone monitoring network observations to produce a unique data record of surface ozone (at 14:00 Beijing time) in Beijing from 1995 to 2020. Using this merged dataset, we investigate the variability in surface ozone in Beijing on multiple timescales. The long-term change is primarily characterized by a sudden drop in 2011–2012 with an insignificant linear trend during the full period. Based on CAM-chem model simulations, meteorological factors played important roles in the 2011–2012 ozone drop. Before and after this sudden drop, ozone levels in Beijing increased significantly by 0.42 ± 0.27 ppbv year−1 before 2011 and 0.43 ± 0.41 ppbv year−1 after 2013. We also found a substantial increase in the amplitude of the ozone annual cycle in Beijing, which has not been documented in previous studies. This is consistent with ozone increases in summer and ozone decreases in winter. In addition, the results by the Ensemble Empirical Mode Decomposition (EEMD) analysis indicate significant interannual variations in ozone levels in Beijing with different time oscillation periods, which may be associated with natural variabilities and subsequent changes in meteorological conditions.

Decadal changes in emissions of volatile organic compounds (VOCs) from on-road vehicles with intensified automobile pollution control: Case study in a busy urban tunnel in south China.

In the efforts at controlling automobile emissions, it is important to know in what extent air pollutants from on-road vehicles could be truly reduced. In 2014 we conducted tests in a heavily trafficked tunnel in south China to characterize emissions of volatile organic compounds (VOC) from on-road vehicle fleet and compared our results with those obtained in the same tunnel in 2004. Alkanes, aromatics, and alkenes had average emission factors (EFs) of 338, 63, and 42mgkm-1 in 2014 against that of 194, 129, and 160mgkm-1 in 2004, respectively. In 2014, LPG-related propane, n-butane and i-butane were the top three non-methane hydrocarbons (NMHCs) with EFs of 184±21, 53±6 and 31±3mgkm-1; the gasoline evaporation marker i-pentane had an average EF of 17±3mgkm-1; ethylene and propene were the top two alkenes with average EFs of 16±1 and 9.7±0.9mgkm-1, respectively; isoprene had no direct emission from vehicles; toluene showed the highest EF of 11±2mgkm-1 among the aromatics; and acetylene had an average EF of 7±1mgkm-1. While EFs of total NMHCs decreased only 9% from 493±120mgkm-1 in 2004 to 449±40mgkm-1 in 2014, their total ozone formation potential (OFP) decreased by 57% from 2.50×103mgkm-1 in 2004 to 1.10×103mgkm-1 in 2014, and their total secondary organic aerosol formation potential (SOAFP) decreased by 50% from 50mgkm-1 in 2004 to 25mgkm-1 in 2014. The large drop in ozone and SOA formation potentials could be explained by reduced emissions of reactive alkenes and aromatics, due largely to fuel transition from gasoline/diesel to LPG for taxis/buses and upgraded vehicle emission standards.

2009년 7월 22일 부분일식 발생 시 부산지역 기온과 오존농도의 변화 특성

This paper examines the effects of the partial solar eclipse of 22 July 2009 across the Korean peninsular on surface temperature and ozone concentrations in over the Busan metropolitan region (BMR). The observed data in the BMR demonstrated that the solar eclipse phenomenon clearly affects the surface ozone concentration as well as the air temperature. The decrease in temperature ranging from 1.2 to <TEX>$5.4^{\circ}C$</TEX> was observed at 11 meteorological sites during the eclipse as a consequence of the solar radiation decrease. A large temperature drop exceeding <TEX>$4^{\circ}C$</TEX> was observed at most area (8 sites) of the BMR. Significant ozone drop (18~29 ppb) was also observed during the eclipse mainly due to the decreased efficiency of the photochemical ozone formation. The ozone concentration started to decrease at approximately 1 to 2 hours after the event and reached its minimum value for a half hour to 2 hours after maximum eclipse. The rate of ozone fall ranged between 0.18 and 0.49 ppb/min. The comparison between ozone measurements and the expected values derived from the fitted curve analysis showed that the maximum drop in ozone concentrations occurred at noon or 1 PM and was pronounced at industrial areas.

Mathematical analysis of the stratospheric photochemical system

The impact of odd chlorine (Cly) and odd nitrogen (NOy) perturbations (resulting from human activities) and of enhanced H2O‐H2SO4 aerosol load (associated with volcanic activity) on stratospheric ozone (25 km altitude, midlatitudes) is assessed by using a chemical box model in which key heterogeneous reactions on the surface of sulfate aerosol particles are taken into account. The model shows that if transport is ignored, the response of the photochemical system to increased abundances of odd chlorine and odd nitrogen and to enhanced aerosol surface area density is characterized by a multiequilibrium regime. Catastrophic transitions may occur and may produce dramatic reductions in the stratospheric ozone concentration. When the dissipative effects associated with transport are taken into account, the system still exhibits a nonlinear response to external nitrogen and chlorine sources but without multiequilibrium solutions or catastrophic transitions. Over a sensitive interval, small external disturbances applied to model parameters can lead to large changes in the state of the system. For example, the large drop in ozone derived by the model when dissipative transport effects are taken into account corresponds to a degeneracy of the multiequilibrium regime found when dissipative terms are omitted.

Rapid vertical trace gas transport by an isolated midlatitude thunderstorm

During the cloud dynamics and chemistry field experiment CLEOPATRA in the summer of 1992 in southern Germany, the Deutsche Forschungsanstalt für Luft‐ und Raumfahrt (DLR) (German Aerospace Research Establishment) research aircraft Falcon traversed four times the anvil of a severe, isolated thunderstorm. The first two traverses were at 8 km altitude and close to the anvil cloud base, while the second two traverses were at 10 km. During the 8‐km traverse, measured ozone mixing ratios dropped by 13 parts per billion by volume (ppbv) from the ambient cloud free environment to the anvil cloud, while water vapor increased by 0.3 g kg−1. At the 10‐km traverses, ozone dropped by 25 ppbv, while water vapor increased by 0.18 g kg−1. Three‐dimensional numerical thunderstorm simulations were performed to understand the cause of these changes. The simulations included the transport of two chemical inert tracers. Ozone was assumed to be one of them. The initial ozone profile was composed from an ozone routine sounding and the in situ Falcon measurements prior to the thunderstorm development. The second tracer is typical for a surface released pollutant with a nonzero, constant value in the boundary layer but zero above it. The redistribution of both tracers by the storm is calculated and compared with the observations. For the anvil penetration at 10 km, the calculated difference in ozone mixing ratios is 21 ppbv, while for water vapor an increase of 0.25 g kg−1 was found, in good agreement with the observations. To validate the model results, the radar reflectivity was calculated from simulated fields of cloud water, rain, graupel, hail, and snow and ice crystals and compared with observed values. With respect to maximum reflectivity values and spatial scales, again, excellent agreement was achieved. It is concluded that the rapid transport from the boundary layer directly into the anvil level is the most likely cause of the observed ozone decrease and water vapor increase. Entrainment of ozone‐rich environmental air into the anvil cloud occurred but left a protected core with undiluted boundary layer air in the anvil cloud even at a distance of 120 km from the main updraft. Processes such as production of O3 by electrical discharges, chemical reactions of ozone with boundary layer‐released or lightning‐produced nitrogen compounds, scavenging by hydrometeors, and heterogeneous reactions at the surface of ice crystals may occur, but on the timescale of 0.5–1 hour seem to have a negligible influence on the observed ozone drop.

Increased solar ultraviolet‐B associated with record low ozone over Texas

A report (Kerr and McElroy, 1993) about record high solar UV‐B irradiance at 300 nm at Toronto in 1993 suggests that global ozone decline may have caused increased UV‐B elsewhere. This suggestion is consistent with observations of increased UV‐B associated with record low ozone near and around Seguin, Texas, during the summer of 1993. A sharp drop in ozone occurred during late June, and on 23 June total ozone fell to 230 Dobson units, which is 25.7% below the Nimbus‐7/TOMS observed mean for June 20–24 from 1979 to 1991 (310 DU). Direct UV‐B at 300 nm was the highest since ground observations were begun in February 1990. During July and August 1993, the mean total ozone was, respectively, 13% and 10.7% lower than during July and August 1990. When the Sun was not obscured by clouds or haze during July and August 1993, the mean direct irradiance at 300 nm was, respectively, 18.1% and 13.4% higher than during July and August 1990.

Transport into the south polar vortex in early spring

Data collected during the Airborne Antarctic Ozone Experiment during August and September 1987 show conclusively that a photochemical sink and not transport caused the ozone decline during that time. During the period August 23 to September 22, 1987, mixing ratios of trace constitutents with long lifetimes remained relatively constant for fixed potential temperature and latitude. Over the same period the ozone mixing ratio declined by more than 50% inside the polar vortex near 18 km altitude. This observation alone requires a substantial photochemical sink of ozone. The conservative tracer data indicate that the Lagrangian mean vertical velocity cannot have been upward inside the polar vortex where the ozone hole appeared. Tracer and ozone gradients in the region from 54° to 72°S imply that ozone could be transported into the polar vortex during the spring season. Observed gradients of conserved tracers with respect to latitude and potential temperature are used to deduce a relationship between meridional mixing on potential temperature surfaces and mean diabatic descent in the vortex. The observed gradients and time tendency of ozone are then used to infer the magnitude of the effect of ozone transport in mitigating the springtime ozone decline, using an assumed best guess heating rate of 0.2 K d−1. It is estimated that ozone transport increased the requirement for a photochemical sink by about 20%±10% near the 425‐K potential temperature level during the period of the 1987 experiment, so that transport from other latitudes or heights had a relatively weak influence on the development of the ozone hole in 1987. This estimate is also consistent with inferences based on the magnitude of the ozone gradient at the edge of the region of chemical depletion. The sharpness of the observed ozone drop with latitude at the edge of the ozone hole suggests relatively weak lateral mixing there. The tracer data also suggest that the amounts of lateral mixing and subsidence are strong functions of altitude, with more efficient mixing below about 400 K.

Ozone Drop Supports Depletion Theory

Ozone Drop Supports Depletion Theory