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Gao H.,Environment Canada | Gao H.,Lanzhou University | Ma J.,Environment Canada | Cao Z.,Meteorological Service of Canada | And 2 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2010

Following worldwide bans or restrictions, the atmospheric level of many organochlorine pesticides (OCPs) over the Great Lakes exhibited a decreasing trend since the 1980s in various environmental compartments. Atmospheric conditions also influence variation and trend of OCPs. In the present study a nonparametric Mann-Kendall test with an additional process to remove the effect of temporal (serial) correlation was used to detect the temporal trend of OCPs in the atmosphere over the Great Lakes region and to examine the statistical significance of the trends. Using extended time series of measured air concentrations over the Great Lakes region from the Integrated Atmospheric Deposition Network, this study also revisits relationships between seasonal mean air concentration of OCPs and major climate variabilities in the Northern Hemisphere. To effectively extract climate signals from the temporal trend of air concentrations, we detrended air concentrations through removing their linear trend, which is driven largely by their respective half-lives in the atmosphere. The interannual variations of the extended time series show a good association with interannual climate variability, notably, the North Atlantic Oscillation (NAO) and the El Nio-Southern Oscillation. This study demonstrates that the stronger climate signals can be extracted from the detrended time series of air concentrations of some legacy OCPs. The detrended concentration time series also help to interpret, in addition to the connection with interannual variation of the NAO, the links between atmospheric concentrations of OCPs and decadal or interdecadal climate change. Copyright 2010 by the American Geophysical Union.

Ma J.,Environment Canada | Cao Z.,Meteorological Service of Canada
Environmental Science and Technology | Year: 2010

A perturbed air-surface coupled model has been developed to simulate and predict perturbations of POPs concentrations in various environmental media under given climate change scenarios. By introducing the perturbations in air temperature and precipitation induced by climate change in the model, we have examined the corresponding perturbations in the concentration of POPs in the closed air-soil and air-water systems. Numerical experiments for several POPs have been conducted based on the possible future climate change scenarios. It was found that hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), and a polychlorinated biphenyl (PCBs) congener, PCB-153, exhibit strong response to specified climate change scenarios as shown by their high concentrations perturbations in air. In the air-soil system the coupled model predicts 4-50% increases in the air concentrations of these chemicals corresponding to an increase of 0.05-0.1 K yr-1 in the air temperature. Based on our simulations, a 20% increase/decrease in precipitation can result in a 53% and 4% decrease/increase in perturbed air concentration of γ-HCH and α-HCH, respectively. Also, the model can be used to determine the direction of air-surface exchange of POP perturbations induced by climate change. © Published 2010 by the American Chemical Society.

Wilson L.J.,Environment Canada | Giles A.,Meteorological Service of Canada
Meteorological Applications | Year: 2013

A new scoring index is proposed for the verification of the Canadian weather warning program. Called weather warning index (WWI), the new measure is designed to be sensitive to two attributes of warnings, their timeliness and accuracy, and to summarize the verification information into a single value for a representative set of regions of Canada and for several weather elements for which warnings are issued. Given the opposing nature of the two attributes (long lead times are likely to be associated with lower accuracy), it was necessary to carefully balance the score to keep it proper in a general sense. The design decisions for the WWI are presented and discussed, and the score computation is illustrated with sensitivity experiments using 3years of warning forecasts and observations. © 2013 Crown in the right of Canada.

Milrad S.M.,McGill University | Gyakum J.R.,McGill University | Atallah E.H.,McGill University | Smith J.F.,Meteorological Service of Canada
Weather and Forecasting | Year: 2011

The priority of an operational forecast center is to issue watches, warnings, and advisories to notify the public about the inherent risks and dangers of a particular event. Occasionally, events occur that do not meet advisory or warning criteria, but still have a substantial impact on human life and property. Short-lived snow bursts are a prime example of such a phenomenon. While these events are typically characterized by small snow accumulations, they often cause very low visibilities and rapidly deteriorating road conditions, both of which are a major hazard to motorists. On the afternoon of 28 January 2010, two such snow bursts moved through the Ottawa River valley and lower St. Lawrence River valley, and created havoc on area roads, resulting in collisions and injuries. Using the National Centers for Environmental Prediction (NCEP) North American Regional Reanalysis (NARR), these snow bursts were found to be associated with an approaching strong upper-tropospheric trough and the passage of an arctic front. While convection or squall lines are not common in January in Canada, snow bursts are shown to be associated with strong quasigeostrophic forcing for ascent and low-level frontogenesis, in the presence of both convective and conditional symmetric instability. Finally, this paper highlights the need for the development of a standard subadvisory criterion warning of short-lived but high-impact winter weather events, which operational forecasters can issue and quickly disseminate to the general public. © 2011 American Meteorological Society.

Bitar L.,Dalhousie University | Duck T.J.,Dalhousie University | Kristiansen N.I.,Norwegian Institute For Air Research | Stohl A.,Norwegian Institute For Air Research | Beauchamp S.,Meteorological Service of Canada
Journal of Geophysical Research: Atmospheres | Year: 2010

The eruption of Kasatochi volcano on 7-8 August 2008 injected material into the troposphere and lower stratosphere of the northern midlatitudes during a period of low stratospheric aerosol background concentrations. Aerosols from the volcanic plume were detected with a lidar in Halifax, Nova Scotia (44.64°N, 63.59°W) 1 week after the eruption and for the next 4 months thereafter. The volcanic origin of the plume is established using the FLEXPART Lagrangian particle transport model for both the stratosphere and troposphere. The stratospheric plume descended 47.1 ± 2.8 m/d on average as it dispersed, corresponding to a cooling rate of 0.60 ± 0.07 K/d. The descent rate was the same for the tropopause (within statistical uncertainties). The top of the plume remained steady at about 18 km altitude and was likely sustained by vertical eddy diffusion from large-scale horizontal mixing. The lower boundary of the plume descended with the tropopause. The integrated aerosol backscatter between 15 and 19 km altitude was relatively constant at about 8 × 10 -5 sr-1 for 532 nm wavelength. Observations and modeling of Kasatochi aerosols in the middle and lower troposphere indicate a possible ground impact. The volcanic contribution to surface PM2.5 did not exceed 5 g/m3 at the measurement site. Copyright © 2010 by the American Geophysical Union.

Fleming S.W.,Meteorological Service of Canada | Fleming S.W.,University of British Columbia | Sauchyn D.J.,University of Regina
Water Resources Research | Year: 2013

Multidecadal variability can have profound implications for long-term viability of existing water management practices and design of water conveyance, storage, and treatment infrastructure. However, baseline hydrology for water supply planning and engineering design rarely includes the full range of variability and extremes captured by proxies and models of pre- and postinstrumental climate and hydrology. This paper examines the paleohydrology of the Saskatchewan River Basin (SRB), where Canada's fastest growing economy and population are vulnerable to drought and heavily reliant on runoff from the Rocky Mountains. We take a novel approach to time-series analysis of tree-ring reconstructions of the North and South Saskatchewan Rivers. This study evaluates shifts in water availability, volatility as defined in terms of statistical dispersion, and stability as defined in terms of Shannon entropy, between adjacent 30 year windows-corresponding to the standard climatic normal period, and human generational timescales. Broadly speaking, outcomes reveal that gauge records appear unreliable as a basis for long-term water supply planning and engineering design. For example, (1) two preinstrumental periods of stable water deficits represent sustained droughts that current water use and management could not endure, (2) hydroclimatic relationships between the two subbasins, and with the Pacific Decadal Oscillation, change over the generations, and (3) the most anomalous period of the past millennium, with coinciding high levels of availability, volatility, and stability, was about 1890-1920. This happens precisely when the SRB was transformed from prairie and parkland to agricultural land cover-and the precedents for water allocation and use were established. © 2013. American Geophysical Union. All Rights Reserved.

Rasouli K.,University of British Columbia | Hsieh W.W.,University of British Columbia | Cannon A.J.,Meteorological Service of Canada
Journal of Hydrology | Year: 2012

Weather forecast data generated by the NOAA Global Forecasting System (GFS) model, climate indices, and local meteo-hydrologic observations were used to forecast daily streamflows for a small watershed in British Columbia, Canada, at lead times of 1-7. days. Three machine learning methods - Bayesian neural network (BNN), support vector regression (SVR) and Gaussian process (GP) - were used and compared with multiple linear regression (MLR). The nonlinear models generally outperformed MLR, and BNN tended to slightly outperform the other nonlinear models. Among various combinations of predictors, local observations plus the GFS output were generally best at shorter lead times, while local observations plus climate indices were best at longer lead times. The climate indices selected include the sea surface temperature in the Niño 3.4 region, the Pacific-North American teleconnection (PNA), the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO). In the binary forecasts for extreme (high) streamflow events, the best predictors to use were the local observations plus GFS output. Interestingly, climate indices contribute to daily streamflow forecast scores during longer lead times of 5-7. days, but not to forecast scores for extreme streamflow events for all lead times studied (1-7. days). © 2011 Elsevier B.V.

Fleming S.,BC Hydro | Fleming S.,University of British Columbia | Whitfield P.,Meteorological Service of Canada | Whitfield P.,Simon Fraser University
Atmosphere - Ocean | Year: 2010

We assessed the impacts of some key Pacific ocean-atmosphere circulation patterns on annual cycles of temperature and precipitation across British Columbia, Yukon, and southeast Alaska. The El Niño-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and ENSO conditional on PDO states were considered in composite analyses of 71 long, high-quality datasets from surface meteorological stations. Month-by-month, station-by-station Monte Carlo bootstrap tests were employed to assess statistical significance. The results trace precipitation and temperature responses as a function of location, season, and climate mode. In summary, temperature responses were relatively uniform, with higher (lower) temperatures during the warm (cool) phases of these circulation patterns. Nevertheless, strength and seasonal persistence varied considerably with location and climate mode. Impacts were generally most consistent in winter and spring but could extend through most of the year. Overall spatiotemporal patterns in precipitation response were decoupled from those in temperature and were far more heterogeneous. Complexities in precipitation signals included north-south inverse teleconnectivity along the Pacific coast, with a zero-response hinge point in the approximate vicinity of northern Vancouver Island; seasonally opposite anomalies in several interior regions, which might conceivably reflect contrasting effects of Pacific climate modes on wintertime frontal storms versus summertime convective storms; and a consistent lack of substantial response in northwestern British Columbia and possibly southwestern Yukon, conjectured to reflect complications associated with the Icefield Ranges. The product is intended primarily as a basic-level set of climate response maps for hydrologists, biologists, foresters, and others who require empirical assessments of relatively local-scale, year-round ENSO and PDO effects across this broad region.[Traduit par la rédaction] Nous avons évalué les répercussions de certaines configurations de circulation océan Pacifique-atmosphère clés sur les cycles annuels de température et de précipitations en Colombie-Britannique, au Yukon et dans le sud-est de l'Alaska. Nous avons examiné l'El Niño-oscillation australe (ENSO), l'Oscillation décennale du Pacifique (ODP) et la sensibilité de l'ENSO à l'égard des états de l'ODP dans des analyses composites de 71 ensembles de données longs et de bonne qualité de stations météorologiques de surface. Nous avons employé des tests d'amorçage de Monte Carlo mois par mois, station par station, pour mesurer la signification statistique. Les résultats tracent les réponses des précipitations et de la température en fonction de l'endroit, de la saison et du mode climatique. En résumé, les réponses de la température étaient relativement uniformes, avec les températures les plus élevées (basses) durant les phases chaudes (froides) de ces configurations de circulation. Néanmoins, la force et la persistance saisonnière variaient considérablement selon l'endroit et le mode climatique. Les répercussions étaient généralement plus cohérentes en hiver et au printemps mais pouvaient se faire sentir durant la majeure partie de l'année. Généralement, les configurations spatiotemporelles générales dans la réponse des précipitations étaient dissociées de celles de la température et étaient beaucoup plus hétérogè nes. Les complexités dans les signaux de précipitations comprenaient une téléconnexion nord-sud inverse le long de la côte du Pacifique, avec un point charnière de réponse nulle dans le voisinage approximatif du nord de l'île de Vancouver; des anomalies saisonnièrement opposées dans plusieurs régions intérieures, qui pourraient refléter des effets contrastants de modes climatiques du Pacifique sur les tempêtes frontales hivernales par rapport aux tempêtes convectives estivales; et un manque constant de réponse marquée dans le nord-ouest de la Colombie-Britannique et possiblement le sud-ouest du Yukon, que l'on croit attribuables aux complications liées aux chaînons des Glaciers. Le produit est principalement destiné à servir d'ensemble de base de cartes de réponse climatique pour les hydrologistes, les biologistes, les forestiers, etc. qui ont besoin d'évaluations empiriques des effets de l'ENSO et de l'ODP à une échelle assez locale, toute l'année, dans cette grande région.

Komarov S.,Meteorological Service of Canada | Komarov A.,University of Manitoba | Zabeline V.,Meteorological Service of Canada
Canadian Journal of Remote Sensing | Year: 2011

New regression models for the retrieval of marine wind speeds from RADARSAT-2 dual-polarization images and results of the comparative analysis of these models with the C-band geophysical model function CMOD-IFR2 are presented. In the two new models, synthetic aperture radar (SAR) co-polarization (VV) and cross-polarization (VH) radar cross-sections, instrument noise floor, and antenna beam incidence angle were used as independent variables. In addition, one of the models also included wind direction input. To build and test the empirical relationships between wind speed and RADARSAT-2 parameters, we created a database containing 570 samples of ocean buoy wind speed observations collocated and coincident with the information obtained from SAR images. The models were tested on independent wind speed data reaching up to 40 knots. The CMOD_IFR2 was also tested on the same data. Analysis of the test results proved a higher accuracy of the new regression models, including the model without wind direction, as compared with CMOD_IFR2, which uses wind direction information. This means that the degraded accuracy of the SAR wind retrieval model without input of the wind direction can be compensated for by using cross-polarization backscatter information. The models were validated through current buoy and image data, provided by the quasi-operational Wind Information Processing System (WIPS). The developed models have been integrated into and are currently functioning within WIPS (at the Meteorological Service of Canada). © 2012 Government of Canada.

Bernier N.B.,Meteorological Research Division | Belair S.,Meteorological Research Division | Bilodeau B.,Meteorological Research Division | Tong L.,Meteorological Service of Canada
Journal of Hydrometeorology | Year: 2011

A high-resolution 2D near-surface and land surface model was developed to produce snow and temperature forecasts over the complex alpine region of the Vancouver 2010 Winter Olympic and Paralympic Games. The model is driven by downscaled operational outputs from the Meteorological Service of Canada's regional and global forecast models. Downscaling is applied to correct forcings for elevation differences between the operational forecast models and the high-resolution surface model. The high-resolution near-surface and land surface model is then used to further refine the forecasts. The model was validated against temperature and snow depth observations. The largest improvements were found in regions where low-resolution (i.e., on the order of 10 km or more) operational models typically lack the spatial resolution to capture rapid elevation changes. The model was found to better reproduce the intermittent snow cover at low-lying stations and to reduce snow depth error by as much as 3 m at alpine stations. © 2011 American Meteorological Society.

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