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D'Amours R.,University of Alberta | D'Amours R.,Canadian Meteorological Center | Mintz R.,Environment Canada | Mooney C.,Environment Canada | Wiens B.J.,Environment Canada
Journal of Geophysical Research: Atmospheres | Year: 2013

This paper seeks to investigate the extent to which stratosphere-to- troposphere transport (STT) impacts the Canadian Rocky Mountain foothills. Beryllium-7 (7Be) was monitored weekly at Harlech, Alberta, from July 2003 to June 2004, and daily during the spring of 2004. These data, together with hourly ozone (O3) and relative humidity (RH) measurements, are presented and analyzed, with a focus on the spring of 2004. A Lagrangian dispersion model was used to help determine the origin of air parcels arriving at Harlech in order to assess if these periods were related to well-defined stratospheric intrusions. The modeling results show that events consisting of above average surface observations of 7Be and O3, and below average surface observations of RH, are the result of the arrival of air originating from the middle and upper troposphere. During the spring of 2004, no direct STTs were observed; all identified events were determined to be indirect STTs or middle to upper troposphere transport that occurred several days prior to being detected at Harlech. The most significant event occurred between 2 and 11 April, which had the longest period of elevated 7Be and O 3 observations and the lowest RH measured during the spring of 2004, and where the modeling showed a strong stratospheric input. This input can be connected with two well-defined stratospheric intrusions occurring over the northern Pacific Ocean, more than 5 days before the associated surface observations. Furthermore, the modeling shows that periods of below average 7Be and O3 occurred when the station was mainly influenced by air masses circulating in the boundary layer. Key Points 14-day inverse modeling for daily 7Be and O3 in Alberta, March-June 2004Only indirect stratospheric intrusions can be associated to high concentrationsLow concentrations are associated mainly to boundary layer air masses ©2013. American Geophysical Union. All Rights Reserved.


Bidleman T.F.,Umeå University | Bidleman T.F.,Environment Canada | Jantunen L.M.,Environment Canada | Hung H.,Environment Canada | And 4 more authors.
Atmospheric Chemistry and Physics | Year: 2015

Air samples collected during 1994-2000 at the Canadian Arctic air monitoring station Alert (82°30' N, 62°20' W) were analysed by enantiospecific gas chromatography-mass spectrometry for I±-hexachlorocyclohexane (α-HCH), trans-chlordane (TC) and cis-chlordane (CC). Results were expressed as enantiomer fractions (EF Combining double low line peak areas of (+)/[(+) + (and±)] enantiomers), where EFs Combining double low line 0.5, < 0.5 and > 0.5 indicate racemic composition, and preferential depletion of (+) and (-) enantiomers, respectively. Long-term average EFs were close to racemic values for and α-HCH (0.504± 0.004, n = 197) and CC (0.505± 0.004, n=162), and deviated farther from racemic for TC (0.470 ± 0.013, n = 165). Digital filtration analysis revealed annual cycles of lower α-HCH EFs in summer-fall and higher EFs in winter-spring. These cycles suggest volatilization of partially degraded α-HCH with EF < 0.5 from open water and advection to Alert during the warm season, and background transport of α-HCH with EF > 0.5 during the cold season. The contribution of sea-volatilized α-HCH was only 11% at Alert, vs. 32% at Resolute Bay (74.68° N, 94.90° W) in 1999. EFs of TC also followed annual cycles of lower and higher values in the warm and cold seasons. These were in phase with low and high cycles of the TC/CC ratio (expressed as FTC Combining double low line TC/(TC+CC)), which suggests greater contribution of microbially "weathered" TC in summer-fall versus winter-spring. CC was closer to racemic than TC and displayed seasonal cycles only in 1997-1998. EF profiles are likely to change with rising contribution of secondary emission sources, weathering of residues in the environment, and loss of ice cover in the Arctic. Enantiomer-specific analysis could provide added forensic capability to air monitoring programs.


Mctaggart-Cowan R.,Environment Canada | Girard C.,Environment Canada | Plante A.,Canadian Meteorological Center | Desgagne M.,Environment Canada
Monthly Weather Review | Year: 2011

The importance of stratospheric influences for medium-range numerical weather prediction (NWP) of the troposphere has led to increases in the heights of global model domains at operational centers around the world. Grids now routinely extend to 0.1 hPa (approximately 65 km) in these systems, thereby covering the full depth of the stratosphere and the lower portion of the mesosphere. Increasing the vertical extent of higher-resolution limited-area models (LAMs) nested within the global forecasts is problematic because of the computational cost of additional levels and the possibility of inaccuracy or instability in the high-speed stratospheric jets. An upper-boundary nesting (UBN) technique is developed that allows information from high-topped driving grids to influence the evolution of a lower-topped (;10 hPa) LAM integration in a manner analogous to the treatment of lateral boundary conditions. A stratospheric vortex displacement event in the winter of 2007 is used to study the effectiveness of the UBN technique. Tropospheric blocking over Europe leads to the development of an amplifying planetaryscale wave in the lower stratosphere that culminates in an anticyclonic wave break over Asia and a marked increase of wave-1 asymmetry. The rapid evolution of stratospheric potential vorticity (PV) is poorly represented in low-topped models, resulting in PV-induced forecast height errors throughout the depth of the troposphere on time scales as short as 2-5 days. Application of the UBN technique is shown to be an effective way for low-topped configurations to benefit from stratospheric predictability without the problems associated with the inclusion of the stratospheric flow in the higher-resolution model domain. The robustness and relative ease of implementation of the UBN technique may make this computationally inexpensive strategy attractive for a wide range of NWP applications. © 2011 American Meteorological Society.


Theriault J.M.,U.S. National Center for Atmospheric Research | Theriault J.M.,University of Quebec at Montréal | Rasmussen R.,U.S. National Center for Atmospheric Research | Smith T.,Environment Canada | And 7 more authors.
Weather and Forecasting | Year: 2012

Accurate forecasting of precipitation phase and intensity was critical information for many of the Olympic venue managers during the Vancouver 2010 Olympic and Paralympic Winter Games. Precipitation forecasting was complicated because of the complex terrain and warm coastal weather conditions in the Whistler area of British Columbia, Canada. The goal of this study is to analyze the processes impacting precipitation phase and intensity during a winter weather storm associated with rain and snow over complex terrain. The storm occurred during the second day of the Olympics when the downhill ski event was scheduled. At 0000 UTC 14 February, 2 h after the onset of precipitation, a rapid cooling was observed at the surface instrumentation sites. Precipitation was reported for 8 h, which coincided with the creation of a nearly 0oC isothermal layer, as well as a shift of the valley flow from up valley to down valley. Widespread snow was reported on Whistler Mountain with periods of rain at the mountain base despite the expectation derived from synoptic-scale models (15-km grid spacing) that the strong warm advection would maintain temperatures above freezing. Various model predictions are compared with observations, and the processes influencing the temperature, wind, and precipitation types are discussed. Overall, this case study provided a well-observed scenario of winter storms associated with rain and snow over complex terrain. © 2012 American Meteorological Society.


Draxler R.,National Oceanic and Atmospheric Administration | Arnold D.,Zentralanstalt fur Meteorologie und Geodynamik | Chino M.,Japan Atomic Energy Agency | Galmarini S.,European Commission - Joint Research Center Ispra | And 11 more authors.
Journal of Environmental Radioactivity | Year: 2015

Five different atmospheric transport and dispersion model's (ATDM) deposition and air concentration results for atmospheric releases from the Fukushima Daiichi nuclear power plant accident were evaluated over Japan using regional 137Cs deposition measurements and 137Cs and 131I air concentration time series at one location about 110km from the plant. Some of the ATDMs used the same and others different meteorological data consistent with their normal operating practices. There were four global meteorological analyses data sets available and two regional high-resolution analyses. Not all of the ATDMs were able to use all of the meteorological data combinations. The ATDMs were configured identically as much as possible with respect to the release duration, release height, concentration grid size, and averaging time. However, each ATDM retained its unique treatment of the vertical velocity field and the wet and dry deposition, one of the largest uncertainties in these calculations. There were 18 ATDM-meteorology combinations available for evaluation. The deposition results showed that even when using the same meteorological analysis, each ATDM can produce quite different deposition patterns. The better calculations in terms of both deposition and air concentration were associated with the smoother ATDM deposition patterns. The best model with respect to the deposition was not always the best model with respect to air concentrations. The use of high-resolution mesoscale analyses improved ATDM performance; however, high-resolution precipitation analyses did not improve ATDM predictions. Although some ATDMs could be identified as better performers for either deposition or air concentration calculations, overall, the ensemble mean of a subset of better performing members provided more consistent results for both types of calculations. © 2013 .


PubMed | Japan Atomic Energy Agency, European Commission - Joint Research Center Ispra, National Oceanic and Atmospheric Administration, Canadian Meteorological Center and 3 more.
Type: | Journal: Journal of environmental radioactivity | Year: 2014

Five different atmospheric transport and dispersion models (ATDM) deposition and air concentration results for atmospheric releases from the Fukushima Daiichi nuclear power plant accident were evaluated over Japan using regional (137)Cs deposition measurements and (137)Cs and (131)I air concentration time series at one location about 110km from the plant. Some of the ATDMs used the same and others different meteorological data consistent with their normal operating practices. There were four global meteorological analyses data sets available and two regional high-resolution analyses. Not all of the ATDMs were able to use all of the meteorological data combinations. The ATDMs were configured identically as much as possible with respect to the release duration, release height, concentration grid size, and averaging time. However, each ATDM retained its unique treatment of the vertical velocity field and the wet and dry deposition, one of the largest uncertainties in these calculations. There were 18 ATDM-meteorology combinations available for evaluation. The deposition results showed that even when using the same meteorological analysis, each ATDM can produce quite different deposition patterns. The better calculations in terms of both deposition and air concentration were associated with the smoother ATDM deposition patterns. The best model with respect to the deposition was not always the best model with respect to air concentrations. The use of high-resolution mesoscale analyses improved ATDM performance; however, high-resolution precipitation analyses did not improve ATDM predictions. Although some ATDMs could be identified as better performers for either deposition or air concentration calculations, overall, the ensemble mean of a subset of better performing members provided more consistent results for both types of calculations.


Fromm M.,U.S. Navy | Lindsey D.T.,National Oceanic and Atmospheric Administration | Servranckx R.,Canadian Meteorological Center | Yue G.,NASA | And 4 more authors.
Bulletin of the American Meteorological Society | Year: 2010

An in-depth characterization of the seasonal occurrence of wildfire, pyroCb, and the resulting smoke plumes in North America is presented. The canonical model of LS aerosol is that the ultimate source/pathway for its material is the troposphere, and that material enters the LS by two primary irreversible mechanisms: slow cross-tropopause ascent in the tropics and rapid injection by volcanic eruptions. Aerosols, being a basic atmospheric constituent, are a fundamental tracer of polluting processes that affect both the troposphere and stratosphere. The day after a pyroCb was identified the absorbing aerosol index (AI) sensed by the Total Ozone Monitoring Spectrometer (TOMS) highlighted a smoke plume with peculiarly large AI values. Since the discovery of smoke in the stratosphere and the pyroCb, only a small number of individual case studies and modeling experiments have been performed.


Fillion L.,Canadian Meteorological Center | Tanguay M.,Canadian Meteorological Center | Lapalme E.,Canadian Meteorological Center | Denis B.,Canadian Meteorological Center | And 7 more authors.
Weather and Forecasting | Year: 2010

This paper describes the recent changes to the regional data assimilation and forecasting system at the Canadian Meteorological Center. A major aspect is the replacement of the currently operational global variable resolution forecasting approach by a limited-area nested approach. In addition, the variational analysis code has been upgraded to allow limited-area three- and four-dimensional variational data assimilation (3D- and 4DVAR) analysis approaches. As a first implementation step, the constraints were to impose similar background error correlation modeling assumptions, equal computer resources, and the use of the same assimilated data. Both bi-Fourier and spherical-harmonics spectral representations of background error correlations were extensively tested for the large horizontal domain considered for the Canadian regional system. Under such conditions, it is shown that the new regional data assimilation and forecasting system performs as well as the current operational system and it produces slightly better 24-h accumulated precipitation scores as judged from an ensemble of winter and summer cases. Because of the large horizontal extent of the regional domain considered, a spherical-harmonics spectral representation of background error correlations was shown to perform better than the bi-Fourier representation, considering all evaluation scores examined in this study. The latter is more suitable for smaller domains and will be kept for the upcoming use in the kilometric-scale local analysis domains in order to support the Canadian Meteorological Center's (CMC's) operations using multiple domains over Canada. The CMC's new regional system [i.e., a regional limited-area 3DVAR data assimilation system coupled to a limited-area model (REG-LAM3D)] is now undergoing its final evaluations before operational transfer. Important model and data assimilation upgrades are currently under development to fully exploit this new system and are briefly presented. © 2010 American Meteorological Society.


Guffanti M.,U.S. Geological Survey | Schneider D.J.,U.S. Geological Survey | Wallace K.L.,U.S. Geological Survey | Hall T.,National Weather Service - NWS | And 2 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2010

The extensive volcanic cloud from Kasatochi's 2008 eruption caused widespread disruptions to aviation operations along Pacific oceanic, Canadian, and U.S. air routes. Based on aviation hazard warnings issued by the National Oceanic and Atmospheric Administration, U.S. Geological Survey, the Federal Aviation Administration, and Meteorological Service of Canada, air carriers largely avoided the volcanic cloud over a 5 day period by route modifications and flight cancellations. Comparison of time coincident GOES thermal infrared (TIR) data for ash detection with Ozone Monitoring Instrument (OMI) ultraviolet data for SO2 detection shows congruent areas of ash and gas in the volcanic cloud in the 2 days following onset of ash production. After about 2.5 days, the area of SO2 detected by OMI was more extensive than the area of ash indicated by TIR data, indicating significant ash depletion by fall out had occurred. Pilot reports of visible haze at cruise altitudes over Canada and the northern United States suggested that SO2 gas had converted to sulfate aerosols. Uncertain about the hazard potential of the aging cloud, airlines coped by flying over, under, or around the observed haze layer. Samples from a nondamaging aircraft encounter with Kasatochi's nearly 3 day old cloud contained volcanic silicate particles, confirming that some fine ash is present in predominantly gas clouds. The aircraft's exposure to ash was insufficient to cause engine damage; however, slightly damaging encounters with volcanic clouds from eruptions of Reventador in 2002 and Hekla in 2000 indicate the possibility of lingering hazards associated with old and/or diffuse volcanic clouds. © 2010 by the American Geophysical Union.


D'Amours R.,Canadian Meteorological Center | Malo A.,Canadian Meteorological Center | Servranckx R.,Canadian Meteorological Center | Bensimon D.,Canadian Meteorological Center | And 2 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2010

The atmospheric transport and dispersion model Modle Lagrangien de Dispersion de Particules d'ordre zéro (MLDP0) has been in use at the Canadian Meteorological Centre (CMC) for several years. The model is employed to support environmental emergency response activities, in the context of CMC's national and international mandates. MLDP0 is a Lagrangian model in which diffusion is modeled according to a random displacement equation (RDE). MLDP0 is an off-line model and is driven with meteorological fields from CMC's Numerical Weather Analysis and Prediction (NWP) system. MLDP0 can be executed in forward and inverse modes. During the summer of 2008, the important eruptions at Okmok and Kasatochi, in the Aleutians, were cause of considerable concern to aviation, and the model was used extensively to support the Montreal Volcanic Ash Advisory Centre (VAAC). Qualitative comparisons of satellite imagery and MLDP0 outputs show that the model accurately simulated the behavior of volcanic plumes. Inverse simulations based on SO2 observations of the Okmok plume, at the Washington State University campus in Pullman, Washington, yield emission estimates that agree well with those derived from AURA/OMI. Forward simulations using AURA/OMI SO2 emission estimates for the Kasatochi eruption of 7 August also compare quite well quantitatively with observations from Environment Canada's Brewer spectrophotometers in Toronto, as well as with concentration maps reconstructed from AURA/OMI scans. Copyright 2010 by the American Geophysical Union.

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