Atmosphere-Ocean最新文献

{"title":"Ozone in the troposphere: Measurements, climatology, budget, and trends","authors":"D. Tarasick, R. Slater","doi":"10.3137/ao.460105","DOIUrl":"https://doi.org/10.3137/ao.460105","url":null,"abstract":"Abstract An improved understanding of the global tropospheric ozone budget has recently become of great interest, both in Canada and elsewhere. Improvements in both modelling and measurement have made it possible for weather centres to begin to forecast air quality using numerical weather prediction models. Despite substantial progress, there are many open questions regarding tropospheric ozone photochemistry, long‐range transport and the importance of the stratospheric source; this remains an area of very active research. Since ozone in association with particulate matter causes respiratory problems in humans, trends and forecasting of future surface ozone levels are also of great importance. The current status of measurement and modelling, as well as the current understanding of tropospheric ozone budgets and trends, are reviewed, with an emphasis on Canada within the global context.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2008-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3137/ao.460105","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69581030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stratospheric ozone chemistry","authors":"J. McConnell, Jianbing Jin","doi":"10.3137/ao.460104","DOIUrl":"https://doi.org/10.3137/ao.460104","url":null,"abstract":"Abstract Stratospheric ozone is important in shielding the planet from harmful solar radiation and tropospheric ozone and, while harmful to plants and humans in large amounts is also, in combination with water vapour, a major source of OH radicals which act as a detergent for many chemical species emitted into the troposphere by natural and anthropogenic emissions. This paper presents the chemistry affecting both tropospheric and stratospheric ozone with an emphasis on the stratosphere. In the decade since the last Environment Canada report on stratospheric ozone (Wardle et al. , 1997) there have been many advances in our understanding. Recent studies have shown that inorganic chlorine, which is the main contributor to polar ozone depletion and middle stratospheric ozone reduction, has started to decrease as a result of the implementation of the Montreal Protocol. During this period, Canada launched a small satellite, SCISAT‐1. We discuss the chemical processes related to polar ozone loss, such as chlorine activation and denitrification, using data from SCISAT‐1. These measurements and those from the Microwave Limb Sounder (MLS) instrument on the Aura satellite confirm that the chlorine deactivation in the Arctic is distinct from that in the Antarctic. Recent studies show that our understanding of the middle atmosphere bromine budget needs improvement. Using measured constraints reproduces the polar and extra‐polar ozone loss better. In addition, recent studies have addressed the variation of middle atmosphere ozone with solar variability. These studies have investigated the variation of solar radiation and related energetic particle precipitation (EPP) such as auroral precipitation, solar proton events (SPEs) as well as cosmic rays. Although there was some appreciation of these effects in the past, current three‐dimensional (3‐D) models suggest that the EPP may have a greater effect on middle atmospheric ozone than was previously realized. Stratospheric ozone loss allows the penetration of more ultraviolet (UV) radiation into the lower atmosphere, and thus may result in an increase in the oxidation state of the troposphere and affect tropospheric chemistry. Quantitative assessment of the effect of lightning on the ozone budget of the upper troposphere and lower stratosphere (UTLS) is a current challenge, while increases in the size of commercial aviation fleets have a positive radiative forcing in this region. To include the feedbacks between radiation, chemistry and dynamics associated with atmospheric change, coupled chemistry‐climate models (CCMs) have been developed during the past decade. While these models still require improvement in transport and physical processes they generally predict that the Antarctic ozone layer will recover to the levels prior to 1980 by the middle of this century as a result of decreasing atmospheric chlorine and a cooling stratosphere. According to a recent semi‐empirical relationship between ozone loss and Arct","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2008-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3137/ao.460104","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69581343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Surface ultraviolet radiation","authors":"James B. Kerr, V. Fioletov","doi":"10.3137/ao.460108","DOIUrl":"https://doi.org/10.3137/ao.460108","url":null,"abstract":"Abstract One of the main concerns regarding a decrease in stratospheric ozone is the consequential increasein the amount of ultraviolet (UV) radiation that reaches the lower atmosphere and the Earth's surface. Radiationat UV wavelengths where ozone absorbs strongly is detrimental to most biological species, including humanbeings, so a decrease in stratospheric ozone could have a significant impact on the biosphere. This concern hasled to a significant increase in surface UV radiation research over the last two decades since the ratification ofthe Montreal Protocol. Studies include investigations into understanding the complicated absorption and scatteringprocesses involved in the radiative transfer of UV through the atmosphere as well as research on theimpacts of changes in UV radiation. Factors affecting surface UV radiation will be discussed, resources used tostudy surface UV radiation will be described and progress made in our understanding of surface UV radiationover the past two decades will be reviewed.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2008-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3137/ao.460108","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69581483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ozone: From discovery to protection","authors":"C. Mcelroy, P. Fogal","doi":"10.3137/ao.460101","DOIUrl":"https://doi.org/10.3137/ao.460101","url":null,"abstract":"Abstract Within one hundred and fifty years, ozone has gone from an unknown quantity to a protected species. This paper traces the evolution of the science of the ozone layer and follows modern research efforts to the point where the Montreal Protocol to Protect the Ozone Layer was put into place. The Montreal Protocol deserves special consideration because it is the best example of a case where science rapidly drove policy development to bring about the implementation of a global agreement to protect the environment.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2008-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3137/ao.460101","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69581010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ozone climatology, trends, and substances that control ozone","authors":"V. Fioletov","doi":"10.3137/ao.460103","DOIUrl":"https://doi.org/10.3137/ao.460103","url":null,"abstract":"Abstract Ozone decline observed in the stratosphere over the past three decades has resulted from the accumulation of chlorine‐ and bromine‐containing ozone‐depleting substances (ODSs) in the atmosphere. Production of most of these gases is regulated by the Montreal Protocol and its Amendments and Adjustments. The latest observations show a decline in major ODSs in the troposphere as a result of these regulations. Observed changes in global ozone are in line with those expected based on changes in stratospheric levels of chlorine and bromine. A change in the rate of ozone decline was observed in the mid‐1990s. This paper gives a brief overview of the present knowledge of distribution, variability, and long‐term trends in column ozone and ozone profiles, with a focus on observational results and particularly on Canadian data analysis.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2008-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3137/ao.460103","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69581293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatio‐temporal variability in a mid‐latitude ocean basin subject to periodic wind forcing","authors":"L. Sushama, Michael Ghil, Kayo Ide","doi":"10.3137/ao.450404","DOIUrl":"https://doi.org/10.3137/ao.450404","url":null,"abstract":"Abstract The mid‐latitude ocean's response to time‐dependent zonal wind‐stress forcing is studied using a reduced‐gravity, 1.5‐layer, shallow‐water model in two rectangular ocean basins of different sizes. The small basin is 1000 km × 2000 km and the larger one is 3000 km × 2010 km; the aspect ratio of the larger basin is quite similar to that of the North Atlantic between 20°N and 60°N. The parameter dependence of the model solutions and their spatio‐temporal variability subject to time‐independent wind stress forcing serve as the reference against which the results for time‐dependent forcing are compared. For the time‐dependent forcing case, three zonal‐wind profiles that mimic the seasonal cycle are considered in this study: (1) a fixed‐profile wind‐stress forcing with periodically varying intensity; (2) a wind‐stress profile with fixed intensity, but north–south migration of the mid‐latitude westerly wind maximum; and (3) a north–south migrating profile with periodically varying intensity. Results of the small‐basin simulations show the intrinsic variability found for time‐independent forcing to persist when the intensity of the wind forcing varies periodically. It thus appears that the physics behind the upper ocean's variability is mainly controlled by internal dynamics, although the solutions’ spatial patterns are now more complex, due to the interaction between the external and internal modes of variability. The north–south migration of wind forcing, however, does inhibit the inertial recirculation; its suppression increases with the amplitude of north–south migration in the wind‐stress forcing. Model solutions in the larger rectangular basin and at smaller viscosity exhibit more realistic recirculation gyres, with a small meridional‐to‐zonal aspect ratio, and an elongated eastward jet; the low‐frequency variability of these solutions is dominated by periodicities of 14 and 6–7 years. Simulations performed in this setting with a wind‐stress profile that involves seasonal variations of realistic amplitude in both the intensity and the position of the atmospheric jet show the seven‐year periodicity in the oceanic circulation to be robust. The intrinsic variability is reinforced by the periodic variations in the jet's intensity and weakened by periodic variations in the meridional position; the two effects cancel, roughly speaking, thus preserving the overall characteristics of the seven‐year mode.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2007-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3137/ao.450404","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69580872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Short‐wave radiation and sea ice in Baffin Bay","authors":"E. Dunlap, B. DeTracey, Charles C. L. Tang","doi":"10.3137/ao.450402","DOIUrl":"https://doi.org/10.3137/ao.450402","url":null,"abstract":"Abstract The sensitivity of the annual cycle of ice cover in Baffin Bay to short‐wave radiation is investigated. The Princeton Ocean Model (POM) is used and is coupled with a multi‐category, dynamic‐thermodynamic sea‐ice model in which the surface energy balance governs the growth rates of ice of varying thickness. During spring and summer the short‐wave radiation flux dominates other surface heat fluxes and thus has the greatest effect on the ice melt. The sensitivity of model results to short‐wave radiation is tested using several, commonly used, shortwave parameterizations under climatological, as well as short‐term, atmospheric forcing. The focus of this paper is short‐term and annual variability. It is shown that simulated ice cover is sensitive to the short‐wave radiation formulation during the melting phase. For the Baffin Bay simulation, the differences in the resulting ice area and volume, integrated from May to November, can be as large as 45% and 70%, respectively. The parameterization of the effect of cloud cover on the short‐wave radiation can result in the sea‐ice area and volume changes reaching 20% and 30%, respectively. The variation of the cloud amount represents cloud data error, and has a relatively small effect (less then ±4%) on the simulated ice conditions. This is due to the fact that the effect of cloud cover on the short‐wave radiation flux is largely compensated for by its effect on the net near‐surface long‐wave radiation flux.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2007-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3137/ao.450402","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69581152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The circulation and residence time of the strait of Georgia using a simple mixing‐box approach","authors":"R. Pawlowicz, O. Riche, M. Halverson","doi":"10.3137/ao.450401","DOIUrl":"https://doi.org/10.3137/ao.450401","url":null,"abstract":"Abstract New observations in the Strait of Georgia, British Columbia, Canada show that temperature and dissolved oxygen have a pronounced seasonal cycle, with a spatially varying phase. Phase lags in oscillating systems arise due to internal time scales which can be interpreted in fluid systems as residence times. Exploiting phase we construct a quantitative and internally consistent circulation scheme for this body of water after dividing it into four regions: the Fraser River plume, the surface waters down to 50 m, the intermediate waters down to 200 m, and the deep water. In this scheme the intermediate water, the largest region by volume, is continually renewed, and its characteristics change in response to continuous changes in the characteristics of source waters. The dependence of the estuarine circulation on variations in fresh inflow is weak. The deep water is volumetrically less important, but seasonal changes in the density of oceanic source waters can produce a variation in the overall circulation by driving an additional inflow which leads to both deep renewal and increased upwelling. In turn, this increased upwelling results in lower surface temperatures than might otherwise be expected. Intermediate water residence times are about 160 days. Deep water is renewed once per year in summer and is affected only by vertical diffusion during the rest of the year. Surface water residence times for the entire Strait are a few months at most, but the Fraser River plume has a freshwater residence time of approximately 1 day. In addition, we find that the residence time of oceanic source waters in the Strait is 1.7 years due to a substantial recirculation in Haro Strait. Other consequences of this scheme are consistent with independent estimates of horizontal transports, air‐sea heat fluxes, subsurface oxygen (O2) utilization, and primary production. Finally, analysis of the spatial phase variations suggests that the intermediate inflow enters the Strait as a boundary current along the slopes of the Fraser delta.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2007-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3137/ao.450401","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69581111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A practical approach for the assimilation of cloudy infrared radiances and its evaluation using airs simulated observations","authors":"S. Heilliette, L. Garand","doi":"10.3137/ao.450403","DOIUrl":"https://doi.org/10.3137/ao.450403","url":null,"abstract":"Abstract A variational estimation procedure for the simultaneous retrieval of cloud parameters and thermodynamic profiles from infrared radiances is proposed. The method is based on a cloud emissivity model which accounts for the frequency dependence of cloud absorption and scattering and possible mixed phase situations. An effective cloud top height and emissivity are assumed. Monte Carlo experiments performed in a 1D‐var assimilation context using simulated Atmospheric Infrared Radiance Sounder (AIRS) observations from 100 channels demonstrate the substantial added value, in theory, of cloudy radiance assimilation as opposed to clear‐channel assimilation. Improved temperature and humidity retrievals are obtained for a broad layer above the cloud as well as below cloud level under partial cloud cover conditions. The impact is most pronounced in broken to overcast situations involving mid‐level clouds. In these situations, the effective cloud top height and emissivity are retrieved with estimated rms errors typically lower than 30 hPa and 3%, respectively. Expected relative errors on the retrieved effective particle size are of the order of 30–50%. The methodology is directly applicable to real hyperspectral infrared data upon inclusion, for local estimation, of the cloud parameters in the Canadian 4D‐var assimilation system.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2007-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3137/ao.450403","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69581303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Does the north Atlantic oscillation affect hydrographic properties on the Canadian Atlantic continental shelf?","authors":"B. Petrie","doi":"10.3137/ao.450302","DOIUrl":"https://doi.org/10.3137/ao.450302","url":null,"abstract":"Abstract An analysis of hydrographic data from the eastern Canadian continental shelf indicates that large‐scale spatial patterns of bottom temperature and salinity respond to sustained periods of weak and strong meteorological forcing represented by the winter North Atlantic Oscillation (NAO) index. Warm, salty (cold, fresh) conditions prevail on the Newfoundland‐Labrador Shelf, the eastern Scotian Shelf and the Gulf of St. Lawrence during periods of negative (positive) NAO anomalies. The opposite response is seen on the central and western Scotian Shelf and in the Gulf of Maine. Comparison of years when the NAO anomaly was positive and had the same sign for at least the two preceding years with those years when the NAO anomaly was negative and had the same sign for at least the two preceding years, shows differences in bottom temperature and salinity, at the same location, of up to approximately 2°C and 0.4. A plausible explanation of the pattern lies in a combination of local forcing and the highly advective nature of the oceanography that responds to NAO forcing. Greater westward transport of Labrador Slope Water along the shelf edge and subsequent on‐shelf penetration of hydrographic anomalies during periods of negative NAO anomalies give rise to the dipole nature of the temperature and salinity patterns. The effects on hydrographic properties appear to be integrated over several years of meteorological forcing, again likely related to advection in the region.","PeriodicalId":55434,"journal":{"name":"Atmosphere-Ocean","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2007-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3137/ao.450302","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69580397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}