Trends in health and agricultural indices based on the fourth generation of Canada's homogenized daily temperature dataset are examined for 1949-2024. Health indices are characterized by warm and cold spells, heatwaves and cold waves, indices associated to thermal comfort, and to heating and cooling requirements. Agriculture temperature-based indices include those related to damaging cold and heat, and to growing season. The results show that the frequency and duration of warm spells have increased across Canada, mainly in the northern and western regions, while a small decrease is observed in the frequency and duration of cold spells across the country. Heatwaves are more frequent in Canada, especially in the north, British Columbia and Atlantic provinces whereas the frequency of cold waves has decreased across the country, mostly in the north and west. The number of summer days and hot days above 30 degrees C have increased in the southern regions, although that some decreasing trends are found in the number of hot days in the Prairies. The number of tropical nights (when night temperature remains above 20 degrees C) has increased in southern Ontario and Quebec. Heating degree-days have decreased across the country whereas cooling degree-days have increased at most stations in the south. All agriculture cold-related indices, including ice days and frost days, have decreased. The annual highest daily maximum and lowest daily minimum temperatures have increased during the past 76 years, although that some decreasing trends are found in the highest daily maximum temperature in the Prairies. Overall, the growing season is now longer with an earlier start and later end to the season, and the number of growing degree-days has increased across the country. [Traduit par la r & eacute;daction] Les tendances des indices de sant & eacute; et agricoles, calcul & eacute;s & agrave; partir de la quatri & egrave;me g & eacute;n & eacute;ration de l'ensemble de donn & eacute;es homog & eacute;n & eacute;is & eacute;es sur les temp & eacute;ratures quotidiennes du Canada, sont examin & eacute;es pour 1949-2024. Les indices de sant & eacute; sont caract & eacute;ris & eacute;s par des p & eacute;riodes de chaleur et de froid, des vagues de chaleur et de froid, ainsi que par des indices li & eacute;s au confort thermique et aux besoins en chauffage et en climatisation. Les indices agricoles bas & eacute;s sur la temp & eacute;rature comprennent ceux li & eacute;s aux effets n & eacute;fastes du froid et de la chaleur, ainsi qu'& agrave; la saison de croissance. Les r & eacute;sultats r & eacute;v & egrave;lent que la fr & eacute;quence et la dur & eacute;e des vagues de chaleur sont en hausse partout au Canada, principalement dans les r & eacute;gions du nord et de l'ouest, tandis qu'une l & eacute;g & egrave;re diminution de la fr & eacute;quence et de la dur & eacute;e des vagues de froid est observ & eacute;e & agrave; l'& eacute;chelle nationale. Les vagues de chaleur sont plus fr & eacute;quentes au Canada, notamment dans le nord, en Colombie-Britannique et dans les provinces de l'Atlantique, tandis que la fr & eacute;quence des vagues de froid a diminu & eacute; dans l'ensemble du pays, surtout dans le nord et l'ouest. Le nombre de journ & eacute;es estivales et de journ & eacute;es chaudes (sup & eacute;rieures & agrave; 30 degrees C) a augment & eacute; dans les r & eacute;gions du sud, m & ecirc;me si l'on observe certaines tendances & agrave; la baisse concernant le nombre de journ & eacute;es chaudes dans les Prairies. Le nombre de nuits tropicales (lorsque la temp & eacute;rature nocturne reste sup & eacute;rieure & agrave; 20 degrees C) a augment & eacute; dans le sud de l'Ontario et au Qu & eacute;bec. Les degr & eacute;s-jours de chauffage ont diminu & eacute; dans l'ensemble du pays, tandis que les degr & eacute;s-jours de refroidissement ont augment & eacute; dans la plupart des stations du sud. Tous les indices agricoles li & eacute;s au froid, notamment le nombre de jours de gel et de jours de gel & eacute;e, ont diminu & eacute;. Les temp & eacute;ratures maximales et minimales quotidiennes annuelles les plus & eacute;lev & eacute;es ont augment & eacute; au cours des 76 derni & egrave;res ann & eacute;es, m & ecirc;me si l'on observe certaines tendances & agrave; la baisse pour les temp & eacute;ratures maximales quotidiennes les plus & eacute;lev & eacute;es dans les Prairies. Dans l'ensemble, la saison de croissance est d & eacute;sormais plus longue, avec un d & eacute;but plus pr & eacute;coce et une fin plus tardive, et le nombre de degr & eacute;s-jours de croissance a augment & eacute; dans tout le pays.
Post-tropical Hurricane Fiona (2022) crossed the Gulf of St. Lawrence in Atlantic Canada, generating large waves and strong wave-driven currents in this semi-enclosed coastal sea. In this study, surface waves and circulation conditions were simulated using a dynamically coupled wave-circulation model revealing significant wave heights H-s <= 9.4 m and current speeds >1.0 m s(-1). Good agreement was obtained for bulk wave statistics (r(2) > 0.86 for H-s), and broad-scale validation was achieved over a large area using observations from seven satellite altimeters. Higher resolution modelling of wind-generated waves in Malpeque Bay, a back-barrier bay connected to the Gulf, used a nested grid to simulate the waves in sheltered areas with short fetch. Significant wave heights <= 2.2 m in back-barrier regions, and current speeds <= 1.5 m s(-1) in coastal areas around the barrier islands were simulated. Limitations to wind-wave growth were examined through comparison of stationary and nonstationary simulations (time constraints) and analysis of the ratio of storm translational speed to wave celerity (spatial constraints). The results indicate that despite extreme winds, the wave field remained dominated by locally generated young wind sea. Because the storm footprint was comparable to the horizontal basin scale, translating-fetch resonance and sustained swell development were spatially constrained and stationary simulations overpredicted peak wave heights (by up to similar to 25%) under rapidly evolving wind conditions. These findings demonstrate how basin geometry can fundamentally limit hurricane wave growth in marginal seas, even during extreme events.
The first tornado dataset for Canada covered the years 1950-1979 and allowed a 30-year tornado climatology to be attempted. This was followed by a second 30-year national climatology covering the years 1980-2009. Guided by World Meteorological Organization recommendations, the current study is a 10-year update of the Canadian tornado climatology covering the years 1991-2020. Data conventions and quality control procedures developed by the Northern Tornadoes Project are used to ensure a high-quality, nationally consistent dataset, and are also applied back to 1980 for completeness. The updated 30-year dataset comprises 1948 tornadoes with the vast majority (88%) of these rated F/EF0-1, while 11% had a rating of F/EF2 and only 1% had a rating of F/EF3 or higher. Tornadoes were recorded in nearly every province and territory with the highest annual mean frequency in Ontario (18.5 tornadoes per year). Gridded tornado incidence values were highest in the southern Prairies and southern Ontario with a notable regional maximum in the area west of Toronto, even when only F/EF2 + tornadoes are considered. Tornadoes occurred most frequently from June to August and from 1600 to 1859 LT, inclusive. The median lengths and widths of tornado damage paths are 5615 and 260 m, respectively. F/EF2 + tornadoes were found to peak later in the year and later in the day, with more than double the median path length and path width. A total of 20 tornado outbreaks were identified. [Traduit par la r & eacute;daction] Le premier ensemble de donn & eacute;es sur les tornades au Canada couvrait la p & eacute;riode 1950-1979 et avait permis d'& eacute;tablir une climatologie des tornades sur 30 ans. Il a & eacute;t & eacute; suivi d'une deuxi & egrave;me climatologie nationale sur 30 ans, couvrant la p & eacute;riode 1980-2009. S'appuyant sur les recommandations de l'Organisation m & eacute;t & eacute;orologique mondiale, la pr & eacute;sente & eacute;tude constitue une mise & agrave; jour sur 10 ans de la climatologie des tornades au Canada, couvrant les ann & eacute;es 1991-2020. Les conventions relatives aux donn & eacute;es et les proc & eacute;dures de contr & ocirc;le de la qualit & eacute; & eacute;labor & eacute;es par le Northern Tornadoes Project servent & agrave; garantir un ensemble de donn & eacute;es de haute qualit & eacute; et coh & eacute;rent & agrave; l'& eacute;chelle nationale, et sont & eacute;galement appliqu & eacute;es r & eacute;troactivement jusqu'en 1980 & agrave; des fins d'exhaustivit & eacute;.L'ensemble de donn & eacute;es actualis & eacute; sur 30 ans comprend 1 948 tornades, dont la grande majorit & eacute; (88 %) sont class & eacute;es F/EF0-1, tandis que 11 % ont une classification F/EF2 et seulement 1 % une classification F/EF3 ou sup & eacute;rieure. Des tornades ont & eacute;t & eacute; recens & eacute;es dans presque toutes les provinces et tous les territoires, l'Ontario affichant la fr & eacute;quence annuelle moyenne la plus & eacute;lev & eacute;e (18,5 tornades par an). Les valeurs maill & eacute;es de l'incidence des tornades & eacute;taient les plus & eacute;lev & eacute;es dans le sud des Prairies et le sud de l'Ontario, avec un maximum r & eacute;gional notable dans la r & eacute;gion & agrave; l'ouest de Toronto, m & ecirc;me en ne consid & eacute;rant que les tornades de force F/EF2+.Les tornades se sont produites le plus fr & eacute;quemment de juin & agrave; ao & ucirc;t et entre 16 h 00 et 18 h 59, heure locale, inclusivement. Les longueurs et largeurs m & eacute;dianes des trajectoires de d & eacute;g & acirc;ts caus & eacute;s par les tornades sont respectivement de 5 615 m et 260 m. Il a & eacute;t & eacute; constat & eacute; que les tornades de force F/EF2+ atteignaient leur pic plus tard dans l'ann & eacute;e et plus tard dans la journ & eacute;e, avec une longueur et une largeur m & eacute;dianes de trajectoire plus de deux fois sup & eacute;rieures. Au total, 20 s & eacute;ries de tornades ont & eacute;t & eacute; identifi & eacute;es.
The Fourth-Generation homogenized surface air temperature dataset for Canada (V4) produced by Wan et al. (2025) exhibits differences from the updated Third Generation (V3.1) dataset and other international datasets that appear to be the result of methodological deficiencies. This short comment compares the V4 dataset with V3.1 and six international datasets produced using different methods and source data collections, including the ERA5 reanalysis, illustrating that warming in the V4 dataset is substantially greater than in other datasets. The primary causes of the higher warming appear to be related to a combination of the homogenization methodology choices that depart from established practices and the presence of segments of estimated data, mostly prior to 1970, that are systematically different from, but were not made homogeneous to, the observed data series.
In recent years, machine learning (ML) has gained popularity in the field of weather forecasting, particularly in areas where numerical weather prediction (NWP) models face challenges. One such area is fog prediction. Reduced visibility due to fog events poses serious challenges to transportation and public safety. Accurate representation of microphysics processes, radiation, boundary layer turbulence, and air-surface interaction is crucial in fog prediction. Traditional NWP models face limitations in accurately forecasting fog due to those complex processes. In this study, we propose a post-processing approach that combines the Weather Research and Forecasting (WRF) model forecasts with a machine learning classifier to improve fog prediction by distinguishing between fog and no-fog conditions. Using 12 years of data (2012-2023) for St John's, Newfoundland and Labrador, and Yarmouth, Nova Scotia, Canada, the approach was tested on independent 2024 observations. Compared to forecasts based solely on liquid water content from WRF, the ML model achieved higher skill, with F1-score improvements of 13% at St John's and 18% at Yarmouth. According to the results obtained, this approach demonstrates the potential of ML techniques to enhance operational fog forecasting capabilities. [Traduit par la r & eacute;daction] Au cours des derni & egrave;res ann & eacute;es, l'apprentissage machine (AM) a gagn & eacute; en popularit & eacute; dans le domaine des pr & eacute;visions m & eacute;t & eacute;orologiques, en particulier dans les r & eacute;gions o & ugrave; les mod & egrave;les de pr & eacute;vision num & eacute;rique du temps (PNT) rencontrent des difficult & eacute;s. La pr & eacute;vision du brouillard est l'un de ces domaines. La visibilit & eacute; r & eacute;duite due au brouillard pose de s & eacute;rieux probl & egrave;mes pour les transports et la s & eacute;curit & eacute; publique. Une repr & eacute;sentation pr & eacute;cise des processus microphysiques, du rayonnement, de la turbulence de la couche limite et de l'interaction air-surface est essentielle pour pr & eacute;voir le brouillard. Les mod & egrave;les traditionnels de PNT font face & agrave; des limites dans la pr & eacute;vision pr & eacute;cise du brouillard en raison de ces processus complexes. Dans cette & eacute;tude, nous proposons une approche de post-traitement qui combine les pr & eacute;visions du mod & egrave;le de recherche et de pr & eacute;vision m & eacute;t & eacute;orologique (mod & egrave;le WRF) avec un classificateur d'apprentissage automatique afin d'am & eacute;liorer la pr & eacute;vision du brouillard en distinguant les conditions de brouillard des conditions sans brouillard. En utilisant douze ann & eacute;es de donn & eacute;es (2012-2023) pour St John's (Terre-Neuve-et-Labrador) et Yarmouth (Nouvelle-& Eacute;cosse), au Canada, l'approche a & eacute;t & eacute; mise & agrave; l'essai avec des observations ind & eacute;pendantes de 2024. Comparativement aux pr & eacute;visions bas & eacute;es uniquement sur la teneur en eau liquide du mod & egrave;le WRF, le mod & egrave;le AM a obtenu de meilleurs r & eacute;sultats, avec des am & eacute;liorations du score F1 de 13% & agrave; St John's et de 18% & agrave; Yarmouth. D'apr & egrave;s les r & eacute;sultats obtenus, cette approche montre le potentiel des techniques AM pour am & eacute;liorer les capacit & eacute;s op & eacute;rationnelles de pr & eacute;vision du brouillard.
The Java Sea, a critical marine region within the Indonesian Maritime Continent (IMC), is increasingly experiencing marine heatwaves (MHWs). Despite its ecological and economic importance, the mechanisms driving MHWs in this region remain poorly understood. This study investigates the characteristics, the onset atmospheric drivers, and trends of MHWs in the Java Sea using 0.25 degrees spatial resolution of Optimum Interpolation Sea Surface Temperature (OISST) dataset from 1982 to 2021. Results show a significant increase in MHW frequency and duration. Composite analysis reveals that enhanced net surface heat flux is the key factor in MHW onset, driven primarily by reduced latent heat flux, complemented by increased solar radiation. Weakened wind speeds suppress latent heat loss to the atmosphere, while decreased cloud cover enhances solar radiation input, amplifying SST anomalies. On intraseasonal timescales, the Madden-Julian Oscillation (MJO) modulates MHW occurrence, with Phases 2 and 3 exhibiting the highest frequency of events among the active phases. Furthermore, in the interannual variability, MHWs are found to be more frequent and intense during El Ni & ntilde;o events, underscoring the strong influence of large-scale climate variability. The extreme MHW event of 2015, among the most severe on record, was characterized by prolonged SST anomalies exceeding climatological thresholds, coinciding with a strong El Ni & ntilde;o and dominated by increased shortwave radiation contributions to net surface heat flux.
Global warming intensifies heat stress, which can exceed the human body's coping capacity, negatively impacting health and reducing outdoor labour productivity. This study assesses projected heat stress and its effects on labour capacity in North America at two future global warming levels: 2 degrees C and 4 degrees C above the pre-industrial level. We utilise 3-hourly outputs from the Canadian Regional Climate Model version 4 (CanRCM4) large ensemble under a high emissions scenario to compute the wet-bulb globe temperature (WBGT), a heat stress indicator incorporating both temperature and humidity. We then bias correct model simulations to align with the historical heat stress climatology from the North American Regional Reanalysis (NARR). The corrected WBGT projections are used to evaluate labour capacity loss for light, moderate, and heavy outdoor work. Results indicate that the WBGT will increase more in Canada due to a greater increase in temperature. However, heat stress intensity will increase more in the southern United States, where the climate is already warm and humid. Labour capacity loss for heavy workloads in Louisiana, southern Texas, and northeastern Mexico will rise from the current 40% during summer to over 80% under a 4 degrees C global warming scenario. Labour capacity loss uncertainty increases over time at the grid point scale, but spatial labour capacity loss uncertainty decreases over time for all workloads. Additionally, regions experiencing labour capacity loss will expand northward as global temperature rises. The projected increase in labour capacity loss with global warming should be an important aspect to consider for climate change adaptation. [Traduit par la r & eacute;daction] Le r & eacute;chauffement climatique intensifie le stress d & ucirc; & agrave; la chaleur, qui peut d & eacute;passer la capacit & eacute; d'adaptation du corps humain, ce qui a une incidence n & eacute;gative sur la sant & eacute; et r & eacute;duit la productivit & eacute; du travail en plein air. Cette & eacute;tude & eacute;value le stress d & ucirc; & agrave; la chaleur projet & eacute; et ses effets sur la capacit & eacute; de main-d'oe uvre en Am & eacute;rique du Nord & agrave; deux niveaux futurs de r & eacute;chauffement climatique : 2 degrees C et 4 degrees C au-dessus du niveau pr & eacute;industriel. Nous utilisons les r & eacute;sultats toutes les trois heures du grand ensemble de la version 4 du Mod & egrave;le r & eacute;gional canadien du climat (MRCC4) dans un sc & eacute;nario & agrave; & eacute;missions & eacute;lev & eacute;es pour calculer la temp & eacute;rature au thermom & egrave;tre-globe mouill & eacute;, un indicateur de stress d & ucirc; & agrave; la chaleur qui tient compte & agrave; la fois de la temp & eacute;rature et de l'humidit & eacute;. Nous corrigeons ensuite les simulations du mod & egrave;le afin de les aligner sur la climatologie historique du stress d & ucirc; & agrave; la chaleur provenant de la North American Regional Reanalysis (NARR). Les projections corrig & eacute;es de la temp & eacute;rature au thermom & egrave;tre-globe mouill & eacute; servent & agrave; & eacute;valuer la perte de capacit & eacute; de travail pour les travaux l & eacute;gers, mod & eacute;r & eacute;s et lourds en plein air. Les r & eacute;sultats r & eacute;v & egrave;lent que la temp & eacute;rature au thermom & egrave;tre-globe mouill & eacute; augmentera davantage au Canada en raison d'une augmentation plus importante de la temp & eacute;rature. Toutefois, l'intensit & eacute; du stress d & ucirc; & agrave; la chaleur augmentera davantage dans le sud des & Eacute;tats-Unis, o & ugrave; le climat est d & eacute;j & agrave; chaud et humide. La perte de capacit & eacute; de main-d'oe uvre pour les charges de travail lourdes en Louisiane, dans le sud du Texas et dans le nord-est du Mexique passera de 40 % actuellement pendant l'& eacute;t & eacute; & agrave; plus de 80 % dans un sc & eacute;nario de r & eacute;chauffement climatique de 4 degrees C. L'incertitude li & eacute;e & agrave; la perte de capacit & eacute; de main-d'oe uvre augmente avec le temps & agrave; l'& eacute;chelle des points du r & eacute;seau, mais l'incertitude spatiale li & eacute;e & agrave; la perte de capacit & eacute; de main-d'oe uvre diminue avec le temps pour toutes les charges de travail. En outre, les r & eacute;gions touch & eacute;es par la perte de capacit & eacute; de main-d'oe uvre s'& eacute;tendront vers le nord & agrave; mesure que la temp & eacute;rature mondiale augmentera. L'augmentation pr & eacute;vue de la perte de capacit & eacute; de travail due au r & eacute;chauffement climatique devrait & ecirc;tre un aspect important & agrave; prendre en compte dans l'adaptation au changement climatique.
Characterised by rapid development, flash droughts challenge timely responses and severely affect agricultural productivity, ecological stability, and socioeconomic resilience, making them a critical research focus. Existing studies reveal substantial spatiotemporal disparities in flash droughts identified by different definitions. Although definitional effectiveness varies regionally, systematic evaluation of their regional applicability remains limited. Flash drought definition involves two key components: drought indicator selection and the objective identification method. This study developed four definitions by combining two indicators - the soil moisture (SM) and evapotranspiration stress ratio (ESR) - with two methods: based on the change rate of percentiles (CROP) and based on percentiles of variation (POV). We evaluated definitional impacts on drought identification and validated results against documented flash droughts (2022-2024). The results show that drought indicators exert greater influence than identification methods. SM and ESR show distinct spatial patterns in identifying flash drought hotspots across China. POV criteria are stricter than CROP, requiring further threshold investigation. SM better identifies "high evapotranspiration demand, fast evapotranspiration rates, and relatively low initial SM" events, particularly in the humid region (south of Qinling-Huaihe Line), where flash droughts often manifest as "high-temperature-driven", as evident in the Yangtze River Basin during summer 2022 and in central Sichuan in 2023. In contrast, ESR outperforms for detecting "high onset-stage evapotranspiration demand but limited evapotranspiration due to already very low initial SM" events, which are common in the transition region (north of the Qinling-Huaihe Line and south of Inner Mongolia), where flash droughts are typically "water-deficit-driven", as observed in the Huanghuai region in summer 2024. [Traduit par la r & eacute;daction] Caract & eacute;ris & eacute;es par leur d & eacute;veloppement rapide, les s & eacute;cheresses & eacute;clair rendent difficile toute r & eacute;ponse rapide et ont de graves r & eacute;percussions sur la productivit & eacute; agricole, la stabilit & eacute; & eacute;cologique et la r & eacute;silience socio-& eacute;conomique, ce qui en fait un sujet de recherche essentiel. Les & eacute;tudes existantes r & eacute;v & egrave;lent des disparit & eacute;s spatio-temporelles importantes dans les s & eacute;cheresses & eacute;clair identifi & eacute;es par diff & eacute;rentes d & eacute;finitions. Bien que l'efficacit & eacute; des d & eacute;finitions varie d'une r & eacute;gion & agrave; l'autre, leur & eacute;valuation syst & eacute;matique en termes d'applicabilit & eacute; r & eacute;gionale reste limit & eacute;e. La d & eacute;finition de la s & eacute;cheresse & eacute;clair comporte deux & eacute;l & eacute;ments cl & eacute;s: la s & eacute;lection d'indicateurs de s & eacute;cheresse et une m & eacute;thode d'identification objective. Cette & eacute;tude a & eacute;labor & eacute; quatre d & eacute;finitions en combinant deux indicateurs - l'humidit & eacute; du sol (HS) et le ratio de stress & eacute;vapotranspiratif (RSE) - avec deux m & eacute;thodes: bas & eacute;e sur le taux de variation des percentiles (TVP) et bas & eacute;e sur les percentiles de variation (PV). Nous avons & eacute;valu & eacute; les r & eacute;percussions des d & eacute;finitions sur l'identification des s & eacute;cheresses et valid & eacute; les r & eacute;sultats par rapport aux s & eacute;cheresses soudaines document & eacute;es (2022-2024). Les r & eacute;sultats montrent que les indicateurs de s & eacute;cheresse ont une influence plus importante que les m & eacute;thodes d'identification. L'humidit & eacute; du sol et le RSE pr & eacute;sentent des sch & eacute;mas spatiaux distincts dans l'identification des zones sensibles aux s & eacute;cheresses soudaines en Chine. Les crit & egrave;res PV sont plus stricts que ceux du TVP, ce qui n & eacute;cessite une & eacute;tude plus approfondie des seuils. L'humidit & eacute; du sol identifie mieux les & eacute;v & eacute;nements caract & eacute;ris & eacute;s par << une forte demande en & eacute;vapotranspiration, des taux d'& eacute;vapotranspiration & eacute;lev & eacute;s et une humidit & eacute; du sol initiale relativement faible >>, en particulier dans les r & eacute;gions humides (au sud de la ligne Qinling-Huaihe), o & ugrave; les s & eacute;cheresses soudaines se manifestent souvent sous forme de << s & eacute;cheresses induites par les temp & eacute;ratures & eacute;lev & eacute;es >>, comme on l'a vu dans le bassin du Yangts & eacute; pendant l'& eacute;t & eacute; 2022 et dans le centre du Sichuan en 2023. Par contre, le RSE est plus performant pour d & eacute;tecter les & eacute;v & eacute;nements caract & eacute;ris & eacute;s par << une forte demande d'& eacute;vapotranspiration au d & eacute;but, mais une & eacute;vapotranspiration limit & eacute;e en raison d'une humidit & eacute; du sol initiale d & eacute;j & agrave; tr & egrave;s faible >>, qui sont fr & eacute;quents dans la r & eacute;gion de transition (au nord de la ligne Qinling-Huaihe et au sud de la Mongolie int & eacute;rieure), o & ugrave; les s &
The Eurasian continent, specifically Europe, West Asia, East Asia, and the Russian Far East, experienced anomalously high temperatures during the summer of 2022. The physical drivers of this unusually warm summer are investigated using the dominant empirical orthogonal function (EOF) modes of summer 2-m air temperature over Eurasia for the period 1960-2022. The results indicate that the exceptionally warm conditions were primarily linked to three climatic modes. The first mode, explaining 36.8% of the total variance, represents a background warming trend favouring elevated temperatures. The second mode, accounting for 12.3% of the variance, is closely related to the interannual variability of La Ni & ntilde;a conditions and a pronounced sea surface temperature gradient in the North Atlantic. These factors trigger mid-high-latitude wave trains and modulate the Hadley and Walker circulations, collectively fostering persistent anticyclonic anomalies. The third mode, explaining 11.1% of the variance, corresponds to the Pacific Decadal Oscillation (PDO), which triggers a circumglobal teleconnection pattern that guides wave energy to modulate Eurasian circulation. Diagnoses based on Rossby wave source analysis and wave activity flux further support the dynamical roles of these modes. [Traduit par la r & eacute;daction] Le continent eurasien, plus pr & eacute;cis & eacute;ment, l'Europe, l'Asie occidentale, l'Asie orientale et l'Extr & ecirc;me-Orient russe ont connu des temp & eacute;ratures anormalement & eacute;lev & eacute;es pendant l'& eacute;t & eacute; 2022. Les facteurs physiques & agrave; l'origine de cet & eacute;t & eacute; exceptionnellement chaud sont & eacute;tudi & eacute;s au moyen des modes empiriques orthogonaux (MEO) dominants de la temp & eacute;rature de l'air & agrave; 2 m au-dessus de l'Eurasie pour la p & eacute;riode 1960-2022. Les r & eacute;sultats indiquent que les conditions exceptionnellement chaudes & eacute;taient principalement li & eacute;es & agrave; trois modes climatiques. Le premier mode, qui explique 36,8 % de la variance totale, repr & eacute;sente une tendance g & eacute;n & eacute;rale au r & eacute;chauffement favorisant des temp & eacute;ratures & eacute;lev & eacute;es. Le deuxi & egrave;me mode, qui repr & eacute;sente 12,3 % de la variance, est & eacute;troitement li & eacute; & agrave; la variabilit & eacute; interannuelle des conditions La Ni & ntilde;a et & agrave; un gradient prononc & eacute; de la temp & eacute;rature de surface de la mer dans l'Atlantique Nord. Ces facteurs d & eacute;clenchent des trains d'ondes & agrave; moyenne et haute latitude et modulent les circulations de Hadley et de Walker, favorisant collectivement des anomalies anticycloniques persistantes. Le troisi & egrave;me mode, qui explique 11,1 % de la variance, correspond & agrave; l'oscillation d & eacute;cennale du Pacifique (ODP), qui d & eacute;clenche un sch & eacute;ma de t & eacute;l & eacute;connexion circumglobal qui guide l'& eacute;nergie des ondes pour moduler la circulation eurasienne. Les diagnostics bas & eacute;s sur l'analyse des sources d'ondes de Rossby et le flux d'activit & eacute; des ondes confirment encore davantage le r & ocirc;le dynamique de ces modes.
This paper describes the development of two improved Canadian homogenized monthly precipitation datasets, the CanHomP mlyV2 station dataset, which includes the entire data record of 425 long-term stations across Canada (since 1840 or later), and its gridded version CanGridP mlyV2, which covers the entire Canadian land mass for the 1949-2023 period and southern Canada for 1916-2023. The latter is subsequently used to provide updated estimates of Canada's historical precipitation trends with an assessment of trend representativeness. The V2 datasets benefit from the use of improved station data and metadata and an improved data homogenization procedure, which together result in better spatial consistency of trends than seen in unhomogenized data. Estimates of precipitation trends based on CanGridP mlyV2 also exhibit temperature scaling rates that are more in line with physical expectations than the previous versions of gridded precipitation datasets, which exhibited unphysically high temperature scaling rates. Precipitation is estimated to have increased in most areas from southern Nunavut to the Arctic Archipelago and from Labrador to northeastern Quebec in all seasons. It has also increased in a zonal band around 62 degrees N in summer, and in most areas in British Columbia and along the St. Lawrence River in spring and autumn. The most outstanding variation of trends in seasonal precipitation is seen in a broad band across southern Canada, where winter precipitation has decreased significantly without extensively significant changes in the other seasons. The best estimate of increase in the period 1949-2023 is 9.7% for Canada as a whole, 18.9% for Canada's North, and 7.5% for Canada's South. The estimated rate of change in Canada's annual precipitation expressed as a function of surface air temperature change is 4.9% per 1 & ring;C of warming for the period 1949-2023. Over the century-long period 1916-2023, annual precipitation in Canada's South is estimated to have increased 10.7%. [Traduit par la r & eacute;daction] Cet article d & eacute;crit l'& eacute;laboration de deux ensembles de donn & eacute;es homog & eacute;n & eacute;is & eacute;es sur les pr & eacute;cipitations mensuelles au Canada, l'ensemble de donn & eacute;es de la station CanHomP mlyV2, qui englobe l'ensemble des donn & eacute;es enregistr & eacute;es par 425 stations & agrave; long terme & agrave; travers le Canada (depuis 1840 ou plus tard), ainsi que sa version maill & eacute;e CanGridP mlyV2, qui couvre l'ensemble du territoire canadien pour la p & eacute;riode 1949-2023 et le sud du Canada pour la p & eacute;riode 1916-2023. Cette derni & egrave;re est ensuite utilis & eacute;e pour fournir des estimations actualis & eacute;es des tendances historiques des pr & eacute;cipitations au Canada, accompagn & eacute;es d'une & eacute;valuation de la repr & eacute;sentativit & eacute; des tendances. Les ensembles de donn & eacute;es V2 b & eacute;n & eacute;ficient de l'utilisation de donn & eacute;es et m & eacute;tadonn & eacute;es am & eacute;lior & eacute;es provenant des stations et d'une proc & eacute;dure d'homog & eacute;n & eacute;isation des donn & eacute;es am & eacute;lior & eacute;e, qui, ensemble, permettent d'obtenir une meilleure coh & eacute;rence spatiale des tendances que celle observ & eacute;e dans les donn & eacute;es non homog & eacute;n & eacute;is & eacute;es. Les estimations des tendances des pr & eacute;cipitations bas & eacute;es sur CanGridP mlyV2 pr & eacute;sentent & eacute;galement des taux d'& eacute;chelle de temp & eacute;rature plus conformes aux attentes physiques que les versions pr & eacute;c & eacute;dentes des ensembles de donn & eacute;es maill & eacute;es sur les pr & eacute;cipitations, qui pr & eacute;sentaient des taux d'& eacute;chelle de temp & eacute;rature anormalement & eacute;lev & eacute;s. On estime que les pr & eacute;cipitations ont augment & eacute; dans la plupart des r & eacute;gions, du sud du Nunavut & agrave; l'archipel arctique et du Labrador au nord-est du Qu & eacute;bec, et ce, pendant toutes les saisons. Elles ont & eacute;galement augment & eacute; dans une bande zonale autour de 62 degrees N en & eacute;t & eacute;, ainsi que dans la plupart des r & eacute;gions de la Colombie-Britannique et le long du fleuve Saint-Laurent au printemps et & agrave; l'automne. La variation la plus marqu & eacute;e des tendances en mati & egrave;re de pr & eacute;cipitations saisonni & egrave;res s'observe dans une large bande traversant le sud du Canada, o & ugrave; les pr & eacute;cipitations hivernales ont consid & eacute;rablement diminu & eacute; sans que les autres saisons ne connaissent de changements importants. La meilleure estimation de l'augmentation pour la p & eacute;riode 1949-2023 est de 9,7 % pour l'ensemble du Canada, de 18,9 % pour le nord du Canada et de 7,5 % pour le sud du Canada. Le taux de variation estim & eacute; des pr & eacute;cipitations annuelles au Canada, exprim & eacute; en fonction de la variation de la temp & eacute;rature de l'air & agrave; la surface, est de 4,9 % par 1 degrees C de r & eacute;chauffement pour la p & eacute;riode 1949-2023. Au cours de la p & eacute;riode centenaire allant de 1916 & agrave; 2023, les pr & eacute;cipitations annuelles dans le sud du Canada auraient augment & eacute; de 10,7 %.
Changes in lake ice cover resulting from systematic perturbations to individual meteorological forcing variables are examined here by way of numerical experimentation with a 1-dimensional thermodynamic lake model. Examination of a simplified vertical energy budget suggests that wind speed, air temperature, precipitation, and incoming shortwave radiation are key variables governing the creation and evolution of ice. Synthetic 30-year meteorological forcing datasets over a small boreal lake are generated by replicating 1 year of detailed observations with added Gaussian noise or by a scaling factor to each of these forcing variables in turn, and the impact on lake ice phenology, quality, and maximum thickness analysed. For the wind speed experiments, changes in phenology were nonlinear and asymmetric. For the largest wind speed reductions ice-on was delayed but for increasing mean wind speed perturbations, the ice-on date was essentially unchanged. For large wind speed perturbations of either sign the ice-off date was early, but smaller changes in mean wind speed, of either sign, had no effect. Thus, any significant change in mean wind speed would lead to a reduction in ice cover duration. Ice-on dates were only weakly affected by perturbations to any of the other forcing variables considered, including air temperature. Thus, observational studies that link increasing air temperatures to delays in ice-on should also consider the impacts of wind speed if data are available. Changes in mean air temperature led to changes in ice thickness and duration. Increasing precipitation was found to increase ice thickness as well as the fraction of white ice, while changing mean insolation had a significant impact on ice-off. [Traduit par la r & eacute;daction] Les changements observ & eacute;s dans la couverture de glace des lacs r & eacute;sultant de perturbations syst & eacute;matiques de variables m & eacute;t & eacute;orologiques individuelles sont examin & eacute;s ici au moyen d'une exp & eacute;rience num & eacute;rique r & eacute;alis & eacute;e & agrave; l'aide d'un mod & egrave;le thermodynamique unidimensionnel des lacs. L'examen d'un bilan & eacute;nerg & eacute;tique vertical simplifi & eacute; donne & agrave; penser que la vitesse du vent, la temp & eacute;rature de l'air, les pr & eacute;cipitations et le rayonnement solaire entrant sont des variables cl & eacute;s qui r & eacute;gissent la formation et l'& eacute;volution de la glace. Des ensembles de donn & eacute;es synth & eacute;tiques sur les for & ccedil;ages m & eacute;t & eacute;orologiques sur 30 ans au-dessus d'un petit lac bor & eacute;al sont g & eacute;n & eacute;r & eacute;s en reproduisant une ann & eacute;e d'observations d & eacute;taill & eacute;es avec un bruit gaussien ajout & eacute; ou en appliquant un facteur d'& eacute;chelle & agrave; chacune de ces variables de for & ccedil;age tour & agrave; tour, puis l'impact sur la ph & eacute;nologie, la qualit & eacute; et l'& eacute;paisseur maximale de la glace du lac est analys & eacute;.Pour les exp & eacute;riences sur la vitesse du vent, les changements ph & eacute;nologiques & eacute;taient non lin & eacute;aires et asym & eacute;triques. Pour les r & eacute;ductions les plus importantes de la vitesse du vent, la formation de la glace a & eacute;t & eacute; retard & eacute;e, mais pour les perturbations croissantes de la vitesse moyenne du vent, la date de formation de la glace est rest & eacute;e pratiquement inchang & eacute;e. Pour les perturbations importantes de la vitesse du vent, quelle que soit leur direction, la date de fonte des glaces a & eacute;t & eacute; avanc & eacute;e, mais les changements moins importants de la vitesse moyenne du vent, quelle que soit leur direction, n'ont eu aucun effet. Ainsi, tout changement important de la vitesse moyenne du vent entra & icirc;nerait une r & eacute;duction de la dur & eacute;e de la couverture de glace
While the ocean is known to be an important sink for anthropogenic CO2 emissions, assessing trends in ocean’s uptake and storage of atmospheric CO2 is complicated because changes in the ocean dissolvedinorganic carbon (DIC) concentrations due to natural ocean circulation patterns and flux of anthropogenic CO2 need to be disentangled. In this study, we analyze the interannual and decadal changes in the ocean anthropogenic DIC storage from 1992 to 2022 using data from the physically and biogeochem-ically consistent ECCO-Darwin ocean state estimate model. We use the quasi-conservative tracer C∗ to represent the ocean anthropogenic DIC concentrations and offer several key extensions to previous studies: (1) a longer period of analysis (three decades), (2) analysis including the Arctic Ocean, (3) regular spatio-temporal coverage using annually-averaged data to more accurately estimate the rates of change of C∗. Over the 1992–2022 period, we estimate a total global ocean C∗ increase of 60 Pg C, corresponding to about 28% of total anthropogenic CO2 emissions during this time. The general temporal trend shows a nonlinear increase with accelerating rates of anthropogenic DIC accumulation especially in the last two decades (2002 − 2022), though a slowdown in the increasing rates is found in some parts of the ocean, in particular in high-nutrient low-chlorophyll regions. Empirical Orthogonal Function analysis of the vertically-integrated rates of change of C∗ reveals that the top four modes of interannual variability correspond to the Pacific climate modes, such as El Ni˜no Southern Oscillation, Pacific Decadal Oscillation, and North Pacific Gyre Oscillation.
Speculation surrounds the possibility that increasing world temperatures could trigger a decrease in the heat supplied to the Subpolar North Atlantic (SPNA) by the Gulf Stream (GS) and its extension, the North Atlantic Current (NAC). Here we provide evidence for just such a drop in heat and salt delivery in 2014, leading to the development of a cold fresh anomaly (CFA) in the SPNA and reciprocal warm salty anomaly (WSA) near North America in 2015. These coincident dipoles of heat and salt anomalies first appeared in February-March 2014 when cooling and freshening in the NAC near 45oN, 42oW was reciprocated by warming and increased salinity near 42oN, 50oW. The negative anomalies subsequently migrated north-eastwards along the path of the NAC to constitute the CFA centered on 50oN, 30oW by July 2015 while the reciprocal positive anomalies spread south-westwards to constitute the WSA centered on 40oN, 70oW. Sea surface temperature and height anomaly data revealed a rectangular three-fold structure for the CFA representing the path of the cooled and freshened NAC across the Mid-Atlantic Ridge. Surface current velocity data for early 2014 showed that northwards transport in the NAC was temporarily reversed near its exit from the Mann Eddy, possibly due to an influx of Labrador Sea Water from the Deep Western Boundary Current. We conclude that the unprecedented cooling/freshening of the SPNA and warming/salinification of the North American coastal region in 2014-2015 were reciprocal consequences of an interruption of northwards mass transport in the NAC near its exit from the Mann Eddy. [Traduit par la r & eacute;daction] Des sp & eacute;culations entourent la possibilit & eacute; que la hausse des temp & eacute;ratures mondiales puisse entra & icirc;ner une diminution de la chaleur fournie & agrave; l'Atlantique Nord subpolaire (ANSP) par le Gulf Stream (GS) et son extension, le courant de l'Atlantique Nord (CAN). Nous fournissons ici des preuves d'une telle baisse de l'apport de chaleur et de sel en 2014, qui a men & eacute; au d & eacute;veloppement d'une anomalie froide et fra & icirc;che (AFF) dans l'ANSP et d'une anomalie chaude et sal & eacute;e (ACS) r & eacute;ciproque pr & egrave;s de l'Am & eacute;rique du Nord en 2015. Ces dip & ocirc;les co & iuml;ncidents d'anomalies thermiques et salines sont apparus pour la premi & egrave;re fois en f & eacute;vrier-mars 2014, lorsque le refroidissement et l'adoucissement observ & eacute;s dans le CAN pr & egrave;s de 45 N, 42oO ont & eacute;t & eacute; compens & eacute;s par un r & eacute;chauffement et une hausse de la salinit & eacute; pr & egrave;s de 42oN, 50oO. Les anomalies n & eacute;gatives ont ensuite migr & eacute; vers le nord-est le long de la trajectoire du CAN pour former l'AFF centr & eacute;e sur 50oN, 30oO en juillet 2015, tandis que les anomalies positives r & eacute;ciproques se sont propag & eacute;es vers le sud-ouest pour former l'ACS centr & eacute;e sur 40oN, 70oO. Les donn & eacute;es relatives & agrave; la temp & eacute;rature et & agrave; l'anomalie de hauteur de la surface de la mer ont r & eacute;v & eacute;l & eacute; une structure rectangulaire & agrave; trois volets pour l'AFF, repr & eacute;sentant la trajectoire du CAN refroidi et rafra & icirc;chi & agrave; travers la dorsale m & eacute;dio-atlantique. Les donn & eacute;es sur la vitesse des courants de surface pour le d & eacute;but de 2014 ont montr & eacute; que le transport vers le nord dans le CAN s'est temporairement invers & eacute; pr & egrave;s de sa sortie du tourbillon de Mann, peut-& ecirc;tre en raison d'un afflux d'eau de la mer du Labrador provenant du courant profond de la fronti & egrave;re occidentale. Nous concluons que le refroidissement/rafra & icirc;chissement sans pr & eacute;c & eacute;dent de l'ANSP et le r & eacute;chauffement/salinisation de la r & eacute;gion c & ocirc;ti & egrave;re nord-am & eacute;ricaine en 2014-2015 ont & eacute;t & eacute; les cons & eacute;quences r & eacute;ciproques d'une interruption du transport de masse vers le nord dans le CAN pr & egrave;s de sa sortie du tourbillon de Mann.
Limited long-term snowfall observations make it difficult to document how snowfall is changing across Canada. Proxy snowfall measures derived from more plentiful temperature and precipitation may therefore be helpful. We consider simple partitioning of daily precipitation into rainfall and snowfall based on whether temperature is above or below either 0 degrees C or a station specific threshold. Using daily mean temperature and the fixed 0 degrees C threshold resulted in more accurate estimates of annual and seasonal snow-day number and water equivalent snowfall amount than using daily maximum or daily minimum temperature. Using station-specific thresholds further improved estimation accuracy. Trends estimated from these proxy snowfall indices well match those estimated from observed snowfall data for periods and locations when both are available. The median annual proxy snowfall amount in Canada derived from homogenized daily precipitation and temperature data decreased 2.5% per decade over 1949-2023 south of 60 degrees N and increased 0.5% per decade north of 60 degrees N. Seasonally, annual proxy snowfall amount has changed most rapidly in winter, declining 2.6% per decade in southern Canada and increasing 3.6% per decade in northern Canada. This simple approach improves prospects for the continuation of long-term snowfall monitoring in Canada by exploiting long-term daily precipitation and temperature data. [Traduit par la r & eacute;daction] Le nombre limit & eacute; d'observations & agrave; long terme sur les chutes de neige rend difficile la documentation des changements qui s'op & egrave;rent & agrave; cet & eacute;gard & agrave; travers le Canada. Des mesures indirectes des chutes de neige d & eacute;riv & eacute;es de donn & eacute;es plus abondantes sur la temp & eacute;rature et les pr & eacute;cipitations peuvent donc s'av & eacute;rer utiles. Nous envisageons une simple r & eacute;partition des pr & eacute;cipitations quotidiennes en pluie et en neige, selon que la temp & eacute;rature est sup & eacute;rieure ou inf & eacute;rieure & agrave; 0 degrees C ou & agrave; un seuil propre & agrave; chaque station. L'utilisation de la temp & eacute;rature moyenne quotidienne et du seuil fixe de 0 degrees C a permis d'obtenir des estimations plus pr & eacute;cises du nombre annuel et saisonnier de jours de neige et de la quantit & eacute; de neige & eacute;quivalente en eau que l'utilisation de la temp & eacute;rature maximale ou minimale quotidienne. L'utilisation de seuils propres & agrave; chaque station a encore am & eacute;lior & eacute; la pr & eacute;cision des estimations. Les tendances estim & eacute;es & agrave; partir de ces indices de neige proxy correspondent bien & agrave; celles estim & eacute;es & agrave; partir des donn & eacute;es d'observation des chutes de neige pour les p & eacute;riodes et les lieux o & ugrave; les deux sont disponibles. La quantit & eacute; annuelle m & eacute;diane de neige estim & eacute;e au Canada, calcul & eacute;e & agrave; partir de donn & eacute;es homog & eacute;n & eacute;is & eacute;es sur les pr & eacute;cipitations et les temp & eacute;ratures quotidiennes, a diminu & eacute; de 2,5 % par d & eacute;cennie entre 1949 et 2023 au sud de 60 degrees N et a augment & eacute; de 0,5 % par d & eacute;cennie au nord de 60 degrees N. Sur le plan saisonnier, la quantit & eacute; annuelle estim & eacute;e de neige a chang & eacute; le plus rapidement en hiver, diminuant de 2,6 % par d & eacute;cennie dans le sud du Canada et augmentant de 3,6 % par d & eacute;cennie dans le nord du Canada. Cette approche simple am & eacute;liore les perspectives de poursuite de la surveillance & agrave; long terme des chutes de neige au Canada en exploitant les donn & eacute;es quotidiennes & agrave; long terme sur les pr & eacute;cipitations et les temp & eacute;ratures.
Marine and coastal fog forms mainly from the cooling of warm and moist air advected over a colder sea surface. Atlantic Canada is one of the foggiest regions of the world due to the strong temperature contrast between the two oceanic currents in the vicinity. Recurring periods of low visibility notably disrupt off-shore operations and marine traffic, but also land and air transportation. On longer time-scales, marine fog variability also has a significant impact on the global radiative budget. Clouds, including fog, are the greatest source of uncertainty in the current climate projections because of their complex feedback mechanisms. Meteorological records indicate a significant negative trend in the occurrence of foggy conditions over the past six decades at most airports in Atlantic Canada, with large internal variability, including interannual and interdecadal variations. Using the airport observations, reanalysis data and climate model outputs, we investigated the various variabilities on the trend, at interannual and interdecadal scales, and attempted to address what caused these changes in fog frequency. Our results show that the strength and position of the North Atlantic Subtropical High as well as the sea-surface temperature of the cold and warm waters near Atlantic Canada were highly correlated with fog occurrence. We applied the derived fog indices on climate model outputs and projected the fog trends and variability in the different future climate scenarios. The results from this study will be compared with those obtained from other methods and the implications will be discussed.
The Last Ice Area (LIA) of the Arctic Ocean, spanning the northern coasts of the Canadian Arctic Archipelago and Greenland, is expected to host the last perennial sea ice in the Arctic this century. Knowledge about the long-term evolution of the ocean structure in the LIA is limited due to sparse observations, restricting our ability to identify and understand past change and the impacts of recent climate warming. This study uses a 63-year ocean circulation hindcast simulation from 1958-2021, evaluated with available ocean and sea ice observations, to understand interdecadal changes in the region. Despite this region being resilient to the 20th century sea ice loss observed in most other regions of the Arctic, the model shows that the LIA's sea ice began to experience losses starting in the 2010s, aligned with satellite observations. During the study period, the modelled ocean structure in the LIA was increasingly modified by Atlantic Water (AW), with overall warming influenced by low-frequency variability. Modelled AW metrics, including AW core temperature, core depth, and layer thickness initially decrease from the start of the model run to a minimum in 1970, then increase to reach maximum AW influence on the water column in the 2000s, before subsequently dipping in the 2010s. Most of these modelled ocean properties are broadly consistent with available observations, such as in the AW core, which warmed by 0.3-0.5 degrees to 0.8$<^>{\circ }$degrees C in the model and 0.7$<^>{\circ }$degrees C in the observations. The model suggests a slight cooling and thinning of the AW layer after 2010; however, observations suggest a continued warming of the core through 2023 to 0.78$<^>{\circ }$degrees C. While the model's representation of stratification and water masses in the upper water column needs improvement, and the model presents an overly vertically diffuse AW layer, the warming of the AW layer and the variability of its position in the water column suggests a trend towards the Atlantification of the LIA, a process observed elsewhere in the Arctic. Given the rapid sea ice loss of the past decade and changing ocean properties such as stratification and heat content, further ocean changes are likely. Improved and timely monitoring and modelling is imperative to understanding current changes and potential impacts in the region. [Traduit par la r & eacute;daction] Le dernier & acirc;ge glaciaire (DAG) de l'oc & eacute;an Arctique, qui s'& eacute;tend sur les ctes nord de l'archipel arctique canadien et du Groenland, devrait abriter la dernire banquise p & eacute;renne de l'Arctique au cours de ce sicle. Les connaissances sur l'& eacute;volution & agrave; long terme de la structure oc & eacute;anique au cours du DAG sont limit & eacute;es en raison du manque d'observations, ce qui restreint notre capacit & eacute; & agrave; identifier et & agrave; comprendre les changements pass & eacute;s et les impacts du r & eacute;chauffement climatique r & eacute;cent. Cette & eacute;tude utilize une simulation r & eacute;trospective de la circulation oc & eacute;anique sur 63 ans, de 1958 & agrave; 2021, & eacute;valu & eacute;e au moyen des observations disponibles sur l'oc & eacute;an et la glace de mer, afin de comprendre les changements interd & eacute;cennaux dans la r & eacute;gion. Bien que cette r & eacute;gion ait r & eacute;sist & eacute; & agrave; la perte de glace de mer observ & eacute;e au XXe sicle dans la plupart des autres r & eacute;gions de l'Arctique, le modle r & eacute;vle que la glace de mer du DAG a commenc & eacute; & agrave; diminuer & agrave; partir des ann & eacute;es 2010, ce qui correspond aux observations satellitaires. Au cours de la p & eacute;riode & eacute;tudi & eacute;e, la structure oc & eacute;anique mod & eacute;lis & eacute;e dans le DAG a & eacute;t & eacute; de plus en plus modifi & eacute;e par l'eau atlantique (EA), le r & eacute;chauffement global & eacute;tant influenc & eacute; par la variabilit & eacute; & agrave; basse fr & eacute;quence. Les paramtres mod & eacute;lis & eacute;s de l'EA, notamment la temp & eacute;rature centrale, la profondeur centrale et l'& eacute;paisseur de la couche, ont d'abord diminu & eacute; depuis le d & eacute;but de la simulation pour atteindre un minimum en 1970, puis ont augment & eacute; pour atteindre une influence maximale de l'EA sur la colonne d'eau dans les ann & eacute;es 2000, avant de redescendre dans les ann & eacute;es 2010. La plupart de ces propri & eacute;t & eacute;s oc & eacute;aniques mod & eacute;lis & eacute;es concordent globalement avec les observations disponibles, comme dans le noyau EA, qui s'est r & eacute;chauff & eacute; de 0,3 & agrave; 0,5 degr & eacute; pour atteindre 0,8$<^>{\circ }$degrees C dans le modle et 0,7$<^>{\circ }$degrees C dans les observations. Le modle & eacute;voque un l & eacute;ger refroidissement et un amincissement de la couche EA aprs 2010; cependant, les observations suggrent un r & eacute;chauffement continu du noyau jusqu'en 2023, pour atteindre 0,78$<^>{\circ }$degrees C. Bien que la repr & eacute;sentation par le modle de la stratification et des masses d'eau dans la colonne d'eau sup & eacute;rieure doive tre am & eacute;lior & eacute;e, et que le modle pr & eacute;sente une couche EA trop diffuse verticalement, le r & eacute;chauffement de la couche EA et la variabilit & eacute; de sa position dans la colonne d'eau laissent supposer une tendance & agrave; l'atlantification du DAG, un processus observ & eacute; ailleurs dans l'Arctique. Compte tenu de la fonte rapide de la banquise au cours de la dernire d & eacute;cennie et de l'& eacute;volution des propri & eacute;t & eacute;s oc & eacute;aniques telles que la stratification et la chaleur contenue, d'autres changements oc & eacute;aniques sont &
A numerical ocean model with biogeochemistry has been developed for a domain that spans oceans around Canada: extending to 26 degrees N in the Atlantic and 44 degrees N in the Pacific and including the whole Arctic Ocean. The spatial resolution is similar to 0.25 degrees in longitude/latitude with 75 vertical levels. A series of simulations was conducted to assess the best choices for biogeochemical model parameters across the diverse regions, using a variety of validation data sets including satellite ocean colour (surface chlorophyll and particulate organic carbon, integrated primary production), surface underway pCO2, and depth profiles of oxygen and nitrate concentration from ships and Argo floats. In addition to parameter values, processes examined include interactive sediments, fluvial nutrients, light attenuation by fluvial coloured dissolved organic matter (CDOM), and iron limitation. The results indicate that the optimal parameter set is one that limits phytoplankton losses to grazing and other processes so as to ensure strong biological drawdown of dissolved inorganic carbon and nutrients in spring and summer; both insufficient and excessive drawdown were observed. Sensitivity to other processes such as interactive sediments, fluvial nutrients or CDOM attenuation was weak in most regions. Fluvial nutrients can cause localized reduction of pCO2 by as much as 60 mu atm, and attenuation by CDOM or sequestration of nutrients in the sediment can reduce primary production and zooplankton biomass in regions with large river inputs or broad continental shelves. Iron limitation has a non-negligible effect on the model solution even in regions generally considered iron-replete; a model that successfully spans iron-limited and non-iron-limited domains will require complete and accurate specification of iron sources and sinks. [Traduit par la r & eacute;daction] Un mod & egrave;le oc & eacute;anique num & eacute;rique int & eacute;grant la biog & eacute;ochimie a & eacute;t & eacute; & eacute;labor & eacute; pour un domaine couvrant les oc & eacute;ans autour du Canada : s'& eacute;tendant jusqu'& agrave; 26 degrees N dans l'Atlantique et 44 degrees N dans le Pacifique, et englobant l'ensemble de l'oc & eacute;an Arctique. La r & eacute;solution spatiale est d'environ 0,25 degrees en longitude/latitude avec 75 niveaux verticaux. Une s & eacute;rie de simulations a & eacute;t & eacute; r & eacute;alis & eacute;e afin d'& eacute;valuer les meilleurs choix pour les param & egrave;tres du mod & egrave;le biog & eacute;ochimique dans les diff & eacute;rentes r & eacute;gions, au moyen de divers ensembles de donn & eacute;es de validation, notamment la couleur de l'oc & eacute;an observ & eacute;e par satellite (chlorophylle de surface et carbone organique particulaire, production primaire int & eacute;gr & eacute;e), le pCO2 de surface en cours de navigation et les profils de profondeur de la concentration en oxyg & egrave;ne et en nitrate provenant de navires et de flotteurs Argo. Outre les valeurs des param & egrave;tres, les processus examin & eacute;s comprennent les s & eacute;diments interactifs, les nutriments fluviaux, l'att & eacute;nuation de la lumi & egrave;re par les mati & egrave;res organiques dissoutes color & eacute;es (MODC) fluviales et la limitation en fer. Les r & eacute;sultats r & eacute;v & egrave;lent que l'ensemble de param & egrave;tres optimal est celui qui limite les pertes de phytoplancton dues au broutage et & agrave; d'autres processus afin d'assurer une forte r & eacute;duction biologique du carbone inorganique dissous et des nutriments au printemps et en & eacute;t & eacute;; des r & eacute;ductions insuffisantes et excessives ont & eacute;t & eacute; observ & eacute;es. La sensibilit & eacute; & agrave; d'autres processus tels que les s & eacute;diments interactifs, les nutriments fluviaux ou l'att & eacute;nuation par les MODC & eacute;tait faible dans la plupart des r & eacute;gions. Les nutriments fluviaux peuvent entra & icirc;ner une r & eacute;duction localis & eacute;e du pCO2 pouvant atteindre 60 mu atm, et l'att & eacute;nuation par les MODC ou la s & eacute;questration des nutriments dans les s & eacute;diments peut r & eacute;duire la production primaire et la biomasse zooplanctonique dans les r & eacute;gions o & ugrave; les apports fluviaux sont importants ou les plateaux continentaux & eacute;tendus. La limitation en fer a un effet non n & eacute;gligeable sur la solution mod & eacute;lis & eacute;e, m & ecirc;me dans les r & eacute;gions g & eacute;n & eacute;ralement consid & eacute;r & eacute;es comme riches en fer; un mod & egrave;le qui couvre & agrave; la fois les domaines limit & eacute;s en fer et ceux qui ne le sont pas n & eacute;cessitera une sp & eacute;cification compl & egrave;te et pr & eacute;cise des sources et des puits de fer.
This paper describes the development of an updated Canadian homogenized monthly mean wind speed dataset, CanHomW mlyV2, for the period 1953-2023 and characterizes observed changes in surface wind speed across Canada. Hourly data from 154 stations in Canada were first quality controlled and adjusted for any non-standard anemometer heights. Then, monthly mean wind speed series were derived and subject to a semi-automated comprehensive data homogenization procedure to identify and diminish non-climatic changes. The procedure uses a combination of station metadata and multiple statistical tests with and without using reference series. The results of the automated procedure were reviewed manually. All of the 154 data series were identified to have one or more non-climatic changes, which were diminished by quantile matching adjustments. Station relocation and/or joining (i.e. joining of different stations' data records into one data series), and instrument changes/problems were found to be the main causes of non-climatic changes.The homogenized dataset shows weakening winds in a large part of southern Canada (spanning from the southern Prairies to Labrador) and strengthening winds in most other regions, particularly in the area that spans south-central British Columbia to the Rocky Mountains. The weakening winds in the southern Prairies are also seen consistently in the three modern reanalysis datasets (ERA5, OCADA, 20CRv3), while the four datasets show inconsistent trends in most of the other regions. The Canadian wind trends show notable seasonality, as do the agreement/disagreement among the four datasets. [Traduit par la r & eacute;daction] Le pr & eacute;sent article d & eacute;crit l'& eacute;laboration d'un ensemble de donn & eacute;es homog & eacute;n & eacute;is & eacute;es mises & agrave; jour sur la vitesse moyenne mensuelle du vent au Canada, CanHomW mlyV2, pour la p & eacute;riode 1953-2023, et caract & eacute;rise les changements observ & eacute;s dans la vitesse du vent & agrave; la surface & agrave; travers le Canada. Les donn & eacute;es horaires provenant de 154 stations au Canada ont d'abord fait l'objet d'un contr & ocirc;le de qualit & eacute; et d'un ajustement pour tenir compte des hauteurs non standard des an & eacute;mom & egrave;tres. Ensuite, des s & eacute;ries de vitesses moyennes mensuelles du vent ont & eacute;t & eacute; calcul & eacute;es et soumises & agrave; une proc & eacute;dure semi-automatis & eacute;e d'homog & eacute;n & eacute;isation compl & egrave;te des donn & eacute;es afin d'identifier et de r & eacute;duire les variations non climatiques. La proc & eacute;dure utilise une combinaison de m & eacute;tadonn & eacute;es de station et de multiples tests statistiques avec et sans utilisation de s & eacute;ries de r & eacute;f & eacute;rence. Les r & eacute;sultats de la proc & eacute;dure automatis & eacute;e ont & eacute;t & eacute; v & eacute;rifi & eacute;s manuellement. Les 154 s & eacute;ries de donn & eacute;es ont toutes & eacute;t & eacute; identifi & eacute;es comme pr & eacute;sentant un ou plusieurs changements non climatiques, qui ont & eacute;t & eacute; att & eacute;nu & eacute;s par des ajustements par appariement quantile. Le d & eacute;placement et/ou le regroupement des stations (c'est-& agrave;-dire le regroupement des enregistrements de donn & eacute;es de diff & eacute;rentes stations en une seule s & eacute;rie de donn & eacute;es) et les changements/probl & egrave;mes li & eacute;s aux instruments se sont av & eacute;r & eacute;s & ecirc;tre les principales causes des changements non climatiques.L'ensemble de donn & eacute;es homog & eacute;n & eacute;is & eacute;es montre un affaiblissement des vents dans une grande partie du sud du Canada (du sud des Prairies au Labrador) et un renforcement des vents dans la plupart des autres r & eacute;gions, notamment dans la zone qui s'& eacute;tend du centre-sud de la Colombie-Britannique aux Rocheuses. L'affaiblissement des vents dans le sud des Prairies est & eacute;galement observ & eacute; de mani & egrave;re constante dans les trois ensembles de donn & eacute;es de r & eacute;analyse modernes (ERA5, OCADA, 20CRv3), tandis que les quatre ensembles de donn & eacute;es montrent des tendances incoh & eacute;rentes dans la plupart des autres r & eacute;gions. Les tendances & eacute;oliennes canadiennes pr & eacute;sentent une saisonnalit & eacute; notable, tout comme la concordance/discordance entre les quatre ensembles de donn & eacute;es.
