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The article presents a reply by S. Venkatesh and colleagues to comments made by J. R. Marko and D. B. Fissel about their study, On the Deterioration of Icebergs in the Marginal Ice Zone. According to Venkatesh and colleagues, Marko and Fissel point to the many difficulties and expense in obtaining the necessary data to predict the deterioration of icebergs in an operational time setting. They pointed out that they are confident of the calculated deterioration rates. They said that while the calved iceberg fragments under the existing environmental conditions constitute only 2 to 3% of the original masses, the deterioration rates will increase with increasing water temperatures and sea state conditions.

The article presents a response to a comment on an article about a parametrization of solar energy disposition in the climate system. It was pointed out that the description of the treatment of albedo processes in the University of Victoria model is incorrect. It is agreed that the University of Victoria model has a representation of the ice-albedo feedback through the planetary albedo change. The solar energy disposition is poorly simulated and this aspect is usually neglected in model evaluations.

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Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper provides an updated fresh snowfall water equivalent adjustment factor (ρswe) map for Canada to allow the estimation of solid precipitation amount from ruler measurements of the depth of freshly fallen snow, which has been the standard method for measuring snowfall since Canadian climate measurements began in the middle of the nineteenth century. The ρswe map is created based on the comparison of corrected solid Nipher gauge precipitation to snowfall ruler depth measurements at 175 stations with more than 20 years of concurrent observations. The Nipher gauge correction process involved a careful analysis of station metadata to obtain precise information on anemometer heights and the dates that Nipher gauges were activated. The updated fresh snowfall water equivalent adjustment factor map allows estimates of ρswe to be obtained for all long-term climate stations in Canada. The spatial pattern is consistent with processes influencing the density of fresh snowfall and its initial settling with values ranging from more than 1.5 over the Maritimes to less than 0.8 over southern-central British Columbia.[Traduit par la rédaction] Cet article fournit une carte révisée des facteurs d'ajustement (ρswe) de l'équivalent en eau de la neige fraîche pour le Canada afin de permettre l'estimation des quantités de précipitations solides à partir des mesures d'épaisseur de la neige fraîche faites avec une règle, ce qui constitue la méthode normalisée de mesure des chutes de neige depuis que les mesures climatiques ont débuté au Canada au milieu du dix-neuvième siècle. La carte ρswe est basée sur la comparaison des précipitations solides corrigées obtenues du nivomètre de Nipher aux mesures d'épaisseur de neige faites avec une règle à 175 stations où l'on dispose de plus de 20 années d'observations concurrentes. Le processus de correction des données des nivomètres de Nipher comprenait une analyse minutieuse des métadonnées des stations afin d'obtenir des renseignements précis sur la hauteur des anémomètres et les dates auxquelles les nivomètres de Nipher ont été mis en service. La carte des facteurs d'ajustement de l'équivalent en eau de la neige fraîche permet d'obtenir des estimations de ρswe pour toutes les stations climatiques à long terme au Canada. La configuration spatiale correspond aux processus qui influencent la densité de la neige fraîche et son tassement initial, avec des valeurs allant de plus de 1,5 dans les Maritimes à moins de 0,8 dans le centre-sud de la Colombie-Britannique. [ABSTRACT FROM AUTHOR]

The Circumpolar Flaw Lead (CFL) system study is a Canadian-led International Polar Year (IPY) initiative with over 350 participants from 27 countries. The study is multidisciplinary in nature, integrating physical sciences, biological sciences and Inuvialuit traditional knowledge. The CFL study is designed to investigate the importance of changing climate processes in the flaw lead system of the northern hemisphere on the physical, biogeochemical and biological components of the Arctic marine system. The circumpolar flaw lead is a perennial characteristic of the Arctic throughout the winter season and forms when the mobile multi-year (MY) pack ice moves away from coastal fast ice, creating recurrent and interconnected polynyas in the Norwegian, Icelandic, North American and Siberian sectors of the Arctic. The CFL study was 293 days in duration and involved the overwintering of the Canadian research icebreaker CCGS Amundsen in the Cape Bathurst flaw lead throughout the annual sea-ice cycle of 2007-2008.In this paper we provide an introduction to the CFL project and then use preliminary data from the field season to describe the physical flaw lead system, as observed during the CFL overwintering project. Preliminary data show that ocean circulation is affected by eddy propagation into Amundsen Gulf (AG). Upwelling features arising along the ice edge and along abrupt topography are also detected and identified as important processes that bring nutrient rich waters up to the euphotic zone. Analysis of sea-ice relative vorticity and sea-ice area by ice type in the AG during the CFL study illustrates increased variability in ice vorticity in late autumn 2007 and an increase in new and young ice areas in the AG during winter. Analysis of atmospheric data show that a strong northeast-southwest pressure gradient present over the AG in autumn may be a synoptic-scale atmospheric response to sensible and latent heat fluxes arising from areas of open water persisting into late November 2007. The median atmospheric boundary layer temperature profile over the Cape Bathurst flaw lead during the winter season was stable but much less so when compared to Russian ice island stations.[Traduit par la rédaction] L'étude du système du chenal de séparation circumpolaire (CSC) est une initiative de l'Année polaire internationale (API) menée par le Canada et à laquelle 350 participants provenant de 27 pays ont pris part. L'étude, de nature multidisciplinaire, fait appel aux sciences physiques et biologiques ainsi qu'au savoir traditionnel Inuvialuit. L'étude du CSC vise à examiner les répercussions des processus climatiques changeants dans le système du chenal de séparation de l'hémisphère Nord sur les composantes physiques, biogéochimiques et biologiques du système marin arctique. Le CSC est une caractéristique permanente de l'Arctique durant la saison d'hiver et se forme quand la banquise mobile de glace de plusieurs années s'éloigne de la banquise côtière fixe en créant des polynies récurrentes et interconnectées dans les secteurs norvégien, islandais, nord-américain et sibérien de l'Arctique. Pour mener l'étude du CSC, qui a duré 293 jours, le brise-glace de recherche canadien NGCC Amundsen est demeuré dans le chenal de séparation du cap Bathurst tout l'hiver, c'est-à-dire pendant tout le cycle annuel des glaces de mer de 2007-2008.Dans cet article, nous fournissons une introduction au projet du CSC, puis nous utilisons les données préliminaires de la saison sur le terrain pour décrire le système physique du chenal de séparation, tel qu'observé durant l'hiver du projet du CSC. Les données préliminaires montrent que la circulation océanique est influencée par la propagation de tourbillon dans le golfe d'Amundsen (GA). Des caractéristiques de remontée d'eau le long de la lisière des glaces et le long d'éléments topographiques abrupts ont aussi été observées et identifiées comme des processus importants apportant des eaux riches en nutriments jusqu'à la zone euphotique. L'analyse de la vorticité relative de la glace de mer et de la superficie de la glace de mer par type dans le GA durant l'étude du CSC révèle une variabilité accrue dans la vorticité de la glace à la fin de l'automne 2007 et un accroissement des superficies de nouvelle et de jeune glace dans le GA durant l'hiver. L'analyse des données atmosphériques montre que la présence d'un fort gradient de pression nord est - sud ouest au-dessus du GA en automne peut être une réponse atmosphérique d'échelle synoptique aux flux de chaleur sensible et latente à partir des zones d'eaux libres qui ont persisté jusque vers la fin de novembre 2007. Le profil thermique de la couche limite atmosphérique médiane au-dessus du chenal de séparation du cap Bathurst durant la saison hivernale était stable, mais beaucoup moins que les profils observés aux stations des îles de glace russes. [ABSTRACT FROM AUTHOR]

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Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper reviews recent developments in the theoretical modelling of Boussinesq turbulent plumes in both stratified and unstratified quiescent environments. The review focuses primarily on extensions to the classic entrainment model of Morton et al. (1956; MTT). Recent analytic solutions for the rise height in a stratified environment, for the rise height of turbulent fountains, and for the near-source flow in large area source plumes are reviewed. Extensions to the theory of MTT are then reviewed, including models for plumes with a buoyancy flux that varies with height and for plumes with a buoyancy flux that varies with time. Recent experimental results are also reviewed and compared to these theoretical developments. Some open questions in turbulent plume theory are then discussed. It is shown that MTT are unable to model the rise of weak fountains satisfactorily and the significance of this result for the rise height of plumes in a stratified environment and, more generally, turbulent mixing at a density interface are discussed. The value of the entrainment coefficient α is also discussed. Methods for measuring α are reviewed and variable entrainment models and their limitations are discussed. Finally the appropriate values of α for plumes, jets and fountains are discussed.[Traduit par la rédaction] Cet article examine les développements récents dans la modélisation théorique des panaches turbulents de Boussinesq, dans les environnements calmes tant stratifiés que non stratifiés. L'examen se concentre principalement sur les extensions du modèle d'entraînement classique de Morton et coll. (1956; MTT). Nous examinons des solutions analytiques récentes pour la hauteur d'élévation dans un environnement stratifié, pour la hauteur d'élévation des fontaines turbulentes et pour l'écoulement près de la source dans des panaches de sources de grande surface. Nous examinons ensuite des extensions de la théorie de MTT, y compris des modèles pour des panaches avec un flux de flottabilité variant avec la hauteur et pour des panaches avec un flux de flottabilité variant avec le temps. Nous examinons aussi des résultats expérimentaux récents et nous les comparons à ces avancées théoriques. Nous discutons ensuite de certaines questions actuelles dans la théorie des panaches turbulents. Nous montrons que le MTT ne peut pas modéliser l'élévation de fontaines faibles de fa¸on satisfaisante et nous discutons de l'importance de ce résultat pour la détermination de la hauteur d'élévation des panaches dans un environnement stratifié et, plus généralement, du mélange turbulent à une interface de densité. Nous discutons aussi de la valeur du coefficient d'entraînement α. Nous examinons les méthodes de mesure de α et nous discutons des modèles d'entraînement variable et de leurs limites. Finalement, nous discutons des valeurs appropriées de α pour les panaches, les jets et les fontaines. [ABSTRACT FROM AUTHOR]

Copyright of Atmosphere - Ocean (Canadian Meteorological & Oceanographic Society) is the property of Canadian Meteorological & Oceanographic Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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.RÉSUMÉ [Traduit par la rédaction] La diminution de l'ozone observée dans la stratosphère au cours des trois dernières décennies a été causée par l'accumulation dans l'atmosphère de substances destructrices de la couche d'ozone (SACO) contenant du chlore et du brome. La production de la majorité de ces gaz est réglementée par le Protocole de Montréal et ses modifications et ajustements. Les plus récentes observations montrent que ces réglementations ont mené à une diminution des principales SACO dans la troposphère. Les changements observés dans l'ozone à l'échelle planétaire correspondent à ceux auxquels on s'attendait d'après les changements dans les niveaux stratosphériques de chlore et de brome. Un changement dans le taux de diminution de l'ozone a été observé au milieu des années 1990. Cet article donne un bref aperçu des connaissances actuelles sur la répartition, la variabilité et les tendances à long terme dans la colonne d'ozone et dans les profils d'ozone, en mettant l'accent sur les résultats observés et en particulier sur les analyses de données canadiennes. [ABSTRACT FROM AUTHOR]

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.[Traduit par la rédaction] Il y a 150 ans, l'ozone était un illustre inconnu; c'est aujourd'hui une espèce protégée. Le présent article raconte l'évolution de la science de la couche d'ozone et retrace les efforts de recherche modernes jusqu'au moment où le Protocole de Montréal visant à protéger la couche d'ozone a été mis en place. Le Protocole de Montréal mérite une attention spéciale parce que c'est le meilleur exemple d'un cas où la science a rapidement mené à l'élaboration de politiques ayant pour but la mise en œuvre d'une entente mondiale destinée à protéger l'environnement. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the measurement systems available to make observations of the chemistry of the ozone layer. The characteristics and applications of the data collected are considered. Models provide insight into the physical processes taking place that determine the state of the ozone layer. The properties and uses of a number of models are examined.[Traduit par la rédaction] Cet article donne une vue d'ensemble des systèmes de mesure dont on dispose pour faire des observations de la chimie de la couche d'ozone. Nous examinons les caractéristiques et les applications des données recueillies. Les modèles fournissent des indices sur les processus physiques en jeu qui déterminent l'état de la couche d'ozone. Nous examinons les propriétés et l'utilisation de différents modèles. [ABSTRACT FROM AUTHOR]

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 Arctic meteorological conditions (Rex et al., 2004), a colder Arctic stratosphere may result in more severe ozone loss in the boreal springtime in the near future.[Traduit par la rédaction] L'ozone stratosphérique joue un rôle important en protégeant la planète contre le rayonnement solaire dommageable et l'ozone troposphérique, bien que nocif pour les plantes et les humains en concentration élevée, est aussi, en combinaison avec la vapeur d'eau, une source importante de radicaux OH qui servent de détergent pour plusieurs espèces chimiques introduites dans la troposphère par les émissions naturelles et anthropiques. Cet article porte sur les processus chimiques affectant l'ozone troposphérique et l'ozone stratosphérique, en plaçant la stratosphère au premier plan. Au cours de la décennie, depuis le dernier rapport d'Environnement Canada sur l'ozone stratosphérique (Wardle et coll., 1997), notre compréhension du sujet a progressé à de nombreux égards. Des études récentes ont montré que le chlore inorganique, qui est le principal agent d'appauvrissement de l'ozone polaire et de réduction de l'ozone dans la stratosphère moyenne, a commencé à diminuer par suite de l'application du protocole de Montréal. Durant cette période, le Canada a lancé un petit satellite, le SCISAT-1. Nous discutons des processus chimiques liés à la perte d'ozone polaire, comme l'activation du chlore et la dénitrification, en nous servant des données du SCISAT-1. Ces mesures et celles du sondeur au limbe en hyperfréquence (MLS) du satellite Aura confirment que la désactivation du chlore dans l'Arctique est différente de celle de l'Antarctique. Des études récentes montrent qu'il nous faut améliorer notre compréhension du bilan du brome dans l'atmosphère moyenne. L'emploi de contraintes mesuré [ABSTRACT FROM AUTHOR]

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 seaice 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, short-wave 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.[Traduit par la rédaction] Nous étudions la sensibilité du cycle annuel de la couverture de glace au rayonnement de courtes longueurs d'onde dans la baie de Baffin. Nous nous servons du modèle océanique de Princeton (POM) que nous couplons avec un modèle multicatégorie dynamique-thermodynamique de glaces de mer dans lequel le bilan énergétique de surface gouverne les taux de croissance de glaces de différentes épaisseurs. Durant le printemps et l'été, le flux de rayonnement de courtes longueurs d'onde prédomine sur les autres flux de chaleur à la surface et a donc le plus grand effet sur la fonte de la glace. Nous étudions la sensibilité des résultats du modèle au rayonnement de courtes longueurs d'onde au moyen de plusieurs paramétrisations de courtes longueurs d'onde couramment utilisées pour le forçage climatologique ainsi que pour le forçage météorologique à court terme. Cet article porte principalement sur la variabilité annuelle et à court terme. Nous démontrons que la couverture de glace simulée est sensible à la formulation du rayonnement de courtes longueurs d'onde durant la phase de la fonte. Pour la simulation dans la baie de Baffin, les différences dans l'étendue et le volume résultants, intégrées de mai à novembre, peuvent atteindre 45 % et 70 %, respectivement. La paramétrisation de l'effet de la couverture nuageuse sur le rayonnement de courtes longueurs d'onde peut occasionner des changements dans l'étendue et le volume des glaces de mer atteignant 20 % et 30 %, respectivement. La variation dans l'étendue des nuages représente l'erreur attribuable aux données sur les nuages et n'a qu'un effet relativement faible (moins de ±4 %) sur les conditions glacielles simulées. Cela est dû au fait que l'effet de la couverture nuageuse sur le flux de rayonnement de courtes longueurs d'onde est en grande partie compensé par son effet sur le flux net du rayonnement de grandes longueurs d'onde près de la surface. [ABSTRACT FROM AUTHOR]

Both the earth-reflected shortwave and outgoing longwave radiation (OLR) fluxes at the top of the atmosphere (TOA) as well as surface-absorbed solar fluxes from Canadian Regional Climate Model (CRCM) simulations of the Mackenzie River Basin for the period March 2000 to September 2003 are compared with the radiation fluxes deduced from satellite observations. The differences between the model and satellite solar fluxes at the TOA and at the surface, which are used in this paper to evaluate the CRCM performance, have opposite biases under clear skies and overcast conditions, suggesting that the surface albedo is underestimated while cloud albedo is overestimated. The slightly larger differences between the model and satellite fluxes at the surface compared to those at the TOA indicate the existence of a small positive atmospheric absorption bias in the model. The persistent overestimation of TOA reflected solar fluxes and underestimation of the surface-absorbed solar fluxes by the CRCM under all sky conditions are consistent with the overestimation of cloud fraction by the CRCM... [ABSTRACT FROM AUTHOR]

Winter rainfall is a non-negligible issue for urban drainage in Canada as it can generate significant flooding, especially when it occurs at the same time as high air temperature and in the presence of an appreciable snow cover. According to climate change scenarios, it is expected that the occurrence of these events will increase in a future climate. The purpose of this paper is to perform a trend analysis on six indices related to winter rainfall (January-February) at 60 weather stations located in southern Québec and New Brunswick (Canada) in order to detect possible trends in the frequency or intensity of winter rainfall events during the twentieth century. Datasets were provided by Environment Canada and come from the Canadian Daily Rehabilitated Precipitation Database. The bootstrap-based Mann-Kendall test is used to detect possible non-stationarities in the dataset, while Sen's slope estimator is used to quantify the magnitude of the slope. Results show that 19 stations out of 60 present a significant trend (18 of them being positive) at a 5% level for winter (January-February) total rainfall. In most cases where a trend was detected for winter rainfall there was also an increase in the number of days with rainfall (42% of the stations). These results suggest that globally, for the region under study, rainfall during January and February was more likely to occur, often resulting in a significant increase in the total rainfall during these months... [ABSTRACT FROM AUTHOR]

This paper aims to compare and evaluate the surface energy and water budgets of simulations with the operational version of the Canadian Regional Climate Model (CRCM op) and the developmental version (CRCM dev). The CRCM op and CRCM dev differ in their use of second- and third-generation physical parametrization packages of the Canadian General Circulation Model (CGCM) II and III, respectively. The improvements to the physics of CGCM III include the use of the Canadian LAnd Surface Scheme (CLASS), a three-layer soil model with explicit treatment of snow and canopy layers; it replaces the so-called Bucket hydrological scheme and one-layer force-restore surface energy budget in the CGCM II.The common experimental configuration for this comparison is taken from the Project to Intercompare Regional Climate Simulations (PIRCS-1c) over the continental United States between 1987 and 1994. The analysis focuses on two major river basins with substantial differences in atmospheric forcings, vegetation and topography: the Mississippi and the Columbia river basins... [ABSTRACT FROM AUTHOR]

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The article introduces several papers which deal with water cycle issues within the Mackenzie River basin.

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