Surface Ozone Depletion Research Articles

A signature of aged biogenic compounds detected from airborne VOC measurements in the high arctic atmosphere in March/April 2018

During the PAMARCMiP 2018 campaign (March and April 2018) a proton-transfer-reaction mass spectrometer (PTR-MS) was deployed onboard the POLAR 5 research aircraft and sampled the high Arctic atmosphere under Arctic haze conditions. More than 100 compounds exhibited levels above 1 pmol/mol in at least 25% of the measurements. We used acetone mixing ratios, ozone concentrations, and back trajectories to identify periods with and without long-range transport from continental sources. During two flights, surface ozone depletion events (ODE) were observed that coincided with enhanced levels of acetone, and methylethylketone, and ice nucleating particles (INP).Air masses with continental influence contained elevated levels of compounds associated with aged biogenic emissions and anthropogenic pollution (e.g., methanol, peroxyacetylnitrate (PAN), acetone, acetic acid, methylethylketone (MEK), proprionic acid, and pentanone). Almost half of all positively detected compounds (>100) in the high Arctic atmosphere can be associated with terpene oxidation products, likely produced from monoterpenes and sesquiterpenes emitted from boreal forests. We speculate that the transport of biogenic terpene emissions may constitute an important control of the High Arctic aerosol burden. The sum concentration of the detected aerosol forming vapours is ∼12 pmol/mol, which is of the same order than measured dimethylsulfide (DMS) mixing ratios and their mass density corresponds to approximately one fifth of the measured non-black-carbon particles.

The exceptionally strong and persistent Arctic stratospheric polar vortex in the winter of 2019–2020: 2019-2020冬季北半球超强极涡事件

The Arctic stratospheric polar vortex was exceptional strong, cold and persistent in the winter and spring of 2019–2020. Based on reanalysis data from the National Centers for Environmental Prediction/National Center for Atmospheric Research and ozone observations from the Ozone Monitoring Instrument, the authors investigated the dynamical variation of the stratospheric polar vortex during winter 2019–2020 and its influence on surface weather and ozone depletion. This strong stratospheric polar vortex was affected by the less active upward propagation of planetary waves. The seasonal transition of the stratosphere during the stratospheric final warming event in spring 2020 occurred late due to the persistence of the polar vortex. A positive Northern Annular Mode index propagated from the stratosphere to the surface, where it was consistent with the Arctic Oscillation and North Atlantic Oscillation indices. As a result, the surface temperature in Eurasia and North America was generally warmer than the climatology. In some places of Eurasia, the surface temperature was about 10 K warmer during the period from January to February 2020. The most serious Arctic ozone depletion since 2004 has been observed since February 2020. The mean total column ozone within 60°–90°N from March to 15 April was about 80 DU less than the climatology.摘要2019-2020冬季北极平流层极涡异常并且持续的偏强,偏冷.利用NCEP再数据和OMI臭氧数据, 本文分析了此次强极涡事件中平流层极涡的动力场演变及其对地面暖冬天气和臭氧低值的影响.此次强极涡的形成是由于上传行星波不活跃.持续的强极涡使得2020年春季的最后增温出现时间偏晚.平流层正NAM指数向下传播到地面, 与地面AO指数和NAO指数相一致, 欧亚大陆和北美地面气温均比气候态偏暖, 在欧亚大陆的一些地区, 2020年1月和2月的气温甚至偏高了10K.2020年2月以来北极臭氧出现了2004年以来的最低值, 2020年3-4月60°–90°N的平均臭氧柱总量比气候态偏低了80DU.

Cyclone-induced surface ozone and HDO depletion in the Arctic

Abstract. Ground-based, satellite, and reanalysis datasets were used to identify two similar cyclone-induced surface ozone depletion events at Eureka, Canada (80.1° N, 86.4° W), in March 2007 and April 2011. These two events were coincident with observations of hydrogen deuterium oxide (HDO) depletion, indicating that condensation and sublimation occurred during the transport of the ozone-depleted air masses. Ice clouds (vapour and crystals) and aerosols were detected by lidar and radar when the ozone- and HDO-depleted air masses arrived over Eureka. For the 2007 event, an ice cloud layer was coincident with an aloft ozone depletion layer at 870 m altitude on 2–3 March, indicating this ice cloud layer contained bromine-enriched blowing-snow particles. Over the following 3 days, a shallow surface ozone depletion event (ODE) was observed at Eureka after the precipitation of bromine-enriched particles onto the local snowpack. A chemistry–climate model (UKCA) and a chemical transport model (pTOMCAT) were used to simulate the surface ozone depletion events. Incorporating the latest surface snow salinity data obtained for the Weddell Sea into the models resulted in improved agreement between the modelled and measured BrO concentrations above Eureka. MERRA-2 global reanalysis data and the FLEXPART particle dispersion model were used to study the link between the ozone and HDO depletion. In general, the modelled ozone and BrO showed good agreement with the ground-based observations; however, the modelled BrO and ozone in the near-surface layer are quite sensitive to the snow salinity. HDO depletion observed during these two blowing-snow ODEs was found to be weaker than pure Rayleigh fractionation. This work provides evidence of a blowing-snow sublimation process, which is a key step in producing bromine-enriched sea-salt aerosol.

Airborne lidar measurements of surface ozone depletion over Arctic sea ice

Abstract. A differential absorption lidar (DIAL) for measurement of atmospheric ozone concentration was operated aboard the Polar 5 research aircraft in order to study the depletion of ozone over Arctic sea ice. The lidar measurements during a flight over the sea ice north of Barrow, Alaska, on 3 April 2011 found a surface boundary layer depletion of ozone over a range of 300 km. The photochemical destruction of surface level ozone was strongest at the most northern point of the flight, and steadily decreased towards land. All the observed ozone-depleted air throughout the flight occurred within 300 m of the sea ice surface. A back-trajectory analysis of the air measured throughout the flight indicated that the ozone-depleted air originated from over the ice. Air at the surface that was not depleted in ozone had originated from over land. An investigation into the altitude history of the ozone-depleted air suggests a strong inverse correlation between measured ozone concentration and the amount of time the air directly interacted with the sea ice.

High temporal resolution Br<sub>2</sub>, BrCl and BrO observations in coastal Antarctica

Abstract. There are few observations of speciated inorganic bromine in polar regions against which to test current theory. Here we report the first high temporal resolution measurements of Br2, BrCl and BrO in coastal Antarctica, made at Halley during spring 2007 using a Chemical Ionisation Mass Spectrometer (CIMS). We find indications for an artefact in daytime BrCl measurements arising from conversion of HOBr, similar to that already identified for observations of Br2 made using a similar CIMS method. Using the MISTRA model, we estimate that the artefact represents a conversion of HOBr to Br2 of the order of several tens of percent, while that for HOBr to BrCl is less but non-negligible. If the artefact is indeed due to HOBr conversion, then nighttime observations were unaffected. It also appears that all daytime BrO observations were artefact-free. Mixing ratios of BrO, Br2 and BrCl ranged from instrumental detection limits to 13 pptv (daytime), 45 pptv (nighttime), and 6 pptv (nighttime), respectively. We see considerable variability in the Br2 and BrCl observations over the measurement period which is strongly linked to the prevailing meteorology, and thus air mass origin. Higher mixing ratios of these species were generally observed when air had passed over the sea-ice zone prior to arrival at Halley, than from over the continent. Variation in the diurnal structure of BrO is linked to previous model work where differences in the photolysis spectra of Br2 and O3 is suggested to lead to a BrO maximum at sunrise and sunset, rather than a noon-time maxima. This suite of Antarctic data provides the first analogue to similar measurements made in the Arctic, and of note is that our maximum measured BrCl (nighttime) is less than half of the maximum measured during a similar period (spring-time) in the Arctic (also nighttime). This difference in maximum measured BrCl may also be the cause of a difference in the Br2 : BrCl ratio between the Arctic and Antarctic. An unusual event of trans-continental air mass transport appears to have been responsible for severe surface ozone depletion observed at Halley over a 2-day period. The halogen source region appears to be the Bellingshausen Sea, to the west of the Antarctic Peninsula, with the air mass having spent 3 1/2 days in complete darkness crossing the continent prior to arrival at Halley.

Analysis of reactive bromine production and ozone depletion in the Arctic boundary layer using 3-D simulations with GEM-AQ: inference from synoptic-scale patterns

Abstract. Episodes of high bromine levels and surface ozone depletion in the springtime Arctic are simulated by an online air-quality model, GEM-AQ, with gas-phase and heterogeneous reactions of inorganic bromine species and a simple scheme of air-snowpack chemical interactions implemented for this study. Snowpack on sea ice is assumed to be the only source of bromine to the atmosphere and to be capable of converting relatively stable bromine species to photolabile Br2 via air-snowpack interactions. A set of sensitivity model runs are performed for April 2001 at a horizontal resolution of approximately 100 km×100 km in the Arctic, to provide insights into the effects of temperature and the age (first-year, FY, versus multi-year, MY) of sea ice on the release of reactive bromine to the atmosphere. The model simulations capture much of the temporal variations in surface ozone mixing ratios as observed at stations in the high Arctic and the synoptic-scale evolution of areas with enhanced BrO column amount ("BrO clouds") as estimated from satellite observations. The simulated "BrO clouds" are in modestly better agreement with the satellite measurements when the FY sea ice is assumed to be more efficient at releasing reactive bromine to the atmosphere than on the MY sea ice. Surface ozone data from coastal stations used in this study are not sufficient to evaluate unambiguously the difference between the FY sea ice and the MY sea ice as a source of bromine. The results strongly suggest that reactive bromine is released ubiquitously from the snow on the sea ice during the Arctic spring while the timing and location of the bromine release are largely controlled by meteorological factors. It appears that a rapid advection and an enhanced turbulent diffusion associated with strong boundary-layer winds drive transport and dispersion of ozone to the near-surface air over the sea ice, increasing the oxidation rate of bromide (Br−) in the surface snow. Also, if indeed the surface snowpack does supply most of the reactive bromine in the Arctic boundary layer, it appears to be capable of releasing reactive bromine at temperatures as high as −10 °C, particularly on the sea ice in the central and eastern Arctic Ocean. Dynamically-induced BrO column variability in the lowermost stratosphere appears to interfere with the use of satellite BrO column measurements for interpreting BrO variability in the lower troposphere but probably not to the extent of totally obscuring "BrO clouds" that originate from the surface snow/ice source of bromine in the high Arctic. A budget analysis of the simulated air-surface exchange of bromine compounds suggests that a "bromine explosion" occurs in the interstitial air of the snowpack and/or is accelerated by heterogeneous reactions on the surface of wind-blown snow in ambient air, both of which are not represented explicitly in our simple model but could have been approximated by a parameter adjustment for the yield of Br2 from the trigger.

High ClO and ozone depletion observed in the plume of Sakurajima volcano, Japan

Enhanced BrO and ClO in the boundary layer associated with ozone destruction have been observed over salt lakes, as well as in the polar boundary layer. Volcanic plumes are a major natural source of atmospheric trace gases, influencing the tropospheric and stratospheric trace gas budgets. Though a variety of volcanic gases have been investigated and BrO was found, there is still little information on other halogen oxides (e.g. ClO) in volcanic plumes and the effects on atmospheric ozone. The current belief that volcanic plumes contain ClO has not been quantified to date. Here we report the successful remote measurement of significant amounts of ClO (as well as BrO and SO2) in a volcanic plume from the Sakurajima volcano in Japan, using ground‐based multi‐axis differential optical absorption spectroscopy during May 2004. Additionally halogen‐catalyzed local surface ozone depletion was observed in the vicinity of the volcano.

Photochemical production and loss of organic acids in high Arctic aerosols during long-range transport and polar sunrise ozone depletion events

Abstract Unique daily measurements of water-soluble organics in fine ( 2 μm) aerosols were conducted at Alert in the Canadian Arctic in winter to spring of 1992. They yield insight into photochemical production and loss of organics during long-range transport and ozone depletion events following polar sunrise. Comprehensive analyses of α, ω-dicarboxylic acids (C2–C12), ω-oxocarboxylic acids (C2–C9) and α-dicarbonyls (C2, C3) as well as pyruvic acid and aromatic (phthalic) diacid were conducted using GC and GC/MS techniques. Oxalic (C2) acid was generally the dominant diacid species in both fine and coarse fractions, followed by malonic (C3) and succinic (C4) acids. Concentrations of total diacids in the fine aerosol fraction (0.2–64 ng m−3) were 5–60 times higher than those in the coarse fraction (0.01–3 ng m−3). After polar sunrise in early-March, the total concentration of fine aerosol diacids increased by a factor of 3–5 while the coarse mode did not change significantly. From dark winter to sunlit spring, temporal changes in correlations and ratios of these water-soluble organics to vanadium and sulfate measured simultaneously suggest that atmospheric diacids and related organic compounds are largely controlled by long-range atmospheric transport of polluted air during winter, but they are significantly affected by photochemical production. The latter can occur in sunlight either during transport to the Arctic or during photochemical events associated with surface ozone depletion and bromine chemistry near Alert in spring. Conversion of gaseous precursors to particulate matter via photochemical oxidation was intensified at polar sunrise, resulting in a peak in the ratio of total diacids to V. During ozone depletion events, complex patterns are indicated in photochemical production and loss depending on the diacid compound. Unsaturated (maleic and phthalic) diacids were inversely correlated with particulate Br whereas saturated diacids (C2–C4) positively correlated with particulate Br. These results suggest that Br chemistry associated with ozone depletion leads to degradation of unsaturated diacids and to the production of smaller saturated diacids.

Ocean‐atmosphere‐sea ice‐snowpack interactions in the Arctic, and global change

The discovery of the nature of Arctic haze in the late 1970s and early 1980s [Barrie, 1986] showed that the Arctic is not a pristine environment isolated from human activity, but rather, a region well connected to natural and anthropogenic sources of chemicals by winds, ice movement, and marine currents. Copious pollution is carried on the winds to the Arctic during winter and spring from Europe and northern Asia. The study of this phenomenon led serendipitously to the discovery of ozone depletion chemistry in the Arctic marine boundary layer (MBL) at polar sunrise [Oltmans, 1981; Bottenheim et al., 1986]. In turn, research to understand surface ozone depletion chemistry led to the discovery that it is perturbing the biogeochemical cycle of many elements such as mercury; and that ozone depletion chemistry is likely to have a significant impact on radiative transfer in the atmospheric layer near the surface, with important consequences on the air‐sea exchange of biologically‐mediated compounds.

The Tropospheric Ozone Production about the Spring Equinox (TOPSE) Experiment: Introduction

The Tropospheric Ozone Production about the Spring Equinox (TOPSE) experiment was conducted during February–March, 2000 to study the evolution of tropospheric chemistry at mid to high latitudes over North America. The experiment used airborne in situ and remote sensing measurements of trace gases, radiation, and aerosols, combined with model simulations, to describe the major processes that control evolution of ozone and oxidants during the winter‐spring transition. This paper introduces the major scientific questions of the TOPSE experiment, describes the conduct of the mission, and introduces the scientific results discussed in a series of companion papers in this special section. Among the significant findings of the experiment was that tropospheric ozone increases from winter to spring were dominated by in situ photochemical production in the troposphere, rather than by transport from the stratosphere. Also unique observations of widespread surface ozone depletion events, and of seasonal evolution of trace gases and aerosols as a function of latitude and altitude, were obtained over the course of the mission.

Active Nitrogen in Surface Ozone Depletion Events at Alert during Spring 1998

Measurements of NOx,y were made at Alert, Nunavut, Canada (82.5° N, 62.3° W) during surface layer ozone depletion events. In spring 1998, depletion events were rare and occurred under variable actinic flux, ice fog, and snowfall conditions. NOy changed by less than 10% between normal, partially depleted, and nearly completely depleted ozone air masses. The observation of a diurnal variation in NOx under continuous sunlight supports a source from the snowpack but with rapid conversion to nitrogen reservoirs that are primarily deposited to the surface or airborne ice crystals. It was unclear whether NOx was reduced or enhanced in different stages of the ozone depletion chemistry because of variations in solar and ambient conditions. Because ozone was depleted from 15–20 ppbv to less than 1 ppbv in just over a day in one event it is apparent that the surface source of NOx did not grossly inhibit the removal of ozone. In another case ozone was shown to be destroyed to less than the 0.5 ppbv detection limit of the instrument. However, simple model calculations show that the rate of depletion of ozone and its final steady-state abundance depend sensitively on the strength of the surface source of NOx due to competition from ozone production involving NOx and peroxy radicals. The behavior of the NO/NO2 ratio was qualitatively consistent with enhanced BrO during the period of active ozone destruction. The model is also used to emphasize that the diurnal partitioning of BrOx during ozone depletion events is sensitive to even sub ppbv variations in O3.

Surface ozone depletion episodes in the Arctic and Antarctic from historical ozonesonde records

Abstract. Episodes of ozone depletion in the lowermost Arctic atmosphere (0--2 km) at polar sunrise have been intensively studied at Alert, Canada, and are thought to result from catalytic reactions involving bromine. Recent observations of high concentrations of tropospheric BrO over large areas of the Arctic and Antarctic suggest that such depletion events should also be seen by ozonesondes at other polar stations. An examination of historical ozonesonde records shows that such events occur frequently at Alert, Eureka and Resolute, but much less frequently at Churchill and at other stations. The differences appear to be related to differences in average springtime surface temperatures. The long record at Resolute shows depletions since 1966, but with an increase in their frequency over the period 1966--2000 of 0.66 ± 0.59% per year (95% confidence limits), explaining the apparent increase of Hg in Arctic biota in recent times.

Observations of BrO and its vertical distribution during surface ozone depletion at Alert

During the ALERT2000 polar sunrise experiment at Alert, Nunavut, Canada, we performed measurements of boundary layer bromine oxide radicals (BrO) by differential optical absorption spectroscopy (DOAS) using scattered sunlight in the spectral range from 320 to 400 nm. For the first time the Multi-Axis-(MAX)-DOAS method was applied to derive vertical profile information of BrO. BrO was observed at slant column densities (SCD) of up to 10 15 molecules/cm 2 during a 10-day period of complete surface ozone depletion. The largest BrO column densities were found by observing scattered sunlight from 5° above the horizon, and SCDs were decreasing with increasing elevation angles of the light-receiving telescope. For zenith scattered light the lowest absorption was recorded. Radiative transfer modelling and the calculation of air mass factors show that in most cases the bulk of the observed BrO was present in a layer of 1±0.5 km thickness above the surface (in the boundary layer). The inferred extent of the BrO layer agrees very well with the observed height of the ozone depletion layer ( Bottenheim et al., Atmos. Environ., 2002) from ozone sonde data. Assuming that BrO layer is well-mixed, volume mixing ratios reached levels of 20–30 ppt BrO. These values are consistent with previous measurements of BrO during low ozone events in the Arctic boundary layer.

Measurements of arctic sunrise surface ozone depletion events at Kangerlussuaq, Greenland (67oN, 51oW)

Measurements of arctic sunrise surface ozone depletion events at Kangerlussuaq, Greenland (67oN, 51oW)

Mechanisms for surface ozone depletion and recovery during polar sunrise

As part of the Polar Sunrise Experiment (PSE 94) in April 1994, vertical profiles of ozone concentration, temperature and wind speed above an Arctic Ocean icefloe were obtained to investigate boundary layer ozone depletion. They show sustained periods of depleted surface ozone (<1 ppbv) in a layer 300 to 400 m deep. A one-dimensional model was applied to the data in an attempt to determine the magnitude of chemical destruction rates. The rate of change of ozone corresponding to the combined result of horizontal advection and a volume or a surface sink was calculated to be in the range of −0.001–0.001 ppbv s −1 while the surface deposition velocity was estimated, for most cases, to be in the range of 0.006–0.016 cm s −1. Generally, at this fixed observational point, air mass changes and associated horizontal advection were dominant factors in controlling ozone change. If weak chemical sink rates are to be separated from strong advection changes, future studies will have to take special care to define the horizontal gradient of ozone.

Measurements of arctic sunrise surface ozone depletion events at Kangerlussuaq, Greenland (67°N, 51°W)

In situ measurements of surface ozone were conducted from 30 January through 22 May 1995, at the Sondrestrom Incoherent Scatter Radar Facility near Kangerlussuaq, Greenland. Several periods of depleted ozone were observed, representing the lowest latitude measurements of springtime surface polar ozone depletion in the northern hemisphere to date. The most severe ozone depletion occurred during 14-17 March, when surface ozone levels abruptly fell to below 10 ppbv from typical values of about 40 ppbv. Simultaneous near-ultraviolet and visible total column spectroscopic measurements were made with ground-based instruments, yielding total column values for BrO and OClO. Elevated levels of BrO were observed at the onset of ozone depletion episodes and the behaviour of BrO slant column values through the morning twilight of 15 March indicated that the BrO column must reside in the boundary layer. The boundary layer BrO mixing ratio was estimated at greater than 13 pptv during this episode. OClO levels showed no correlation with surface ozone depletion nor clear evidence of a large tropospheric burden.

Surface ozone depletion in Arctic spring sustained by bromine reactions on aerosols

NEAR-TOTAL depletion of the ozone in surface air is often observed in the Arctic spring, coincident with high atmospheric concentrations of inorganic bromine1–5. Barrie et al.1 suggested that the ozone depletion was due to a catalytic cycle involving the radicals Br and BrO (ref. 6); however, these species are rapidly converted to the nonradical species HBr, HOBr and BrNO3, quenching ozone loss. McConnell et al.7 proposed that cycling of inorganic bromine between aerosols and the gas phase could maintain sufficiently high levels of Br and BrO to destroy ozone, but they did not specify a mechanism for aerosol-phase production of active bromine species. Here we propose such a mechanism, based on known aqueous-phase chemistry, which rapidly converts HBr, HOBr and BrNO3 back to Br and BrO radicals. This mechanism should be particularly efficient in the presence of the high concentrations of sulphuric acid aerosols observed during ozone depletion events3.