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Calgary, Canada

Seguin A.M.,University of Calgary | Seguin A.M.,RWDI AIR Inc. | Norman A.-L.,University of Calgary | Barrie L.,University of Stockholm
Journal of Geophysical Research: Atmospheres | Year: 2014

The influence of frost flowers and seawater brine on ion chemistry in snow, snowpack, ice cores, and aerosols is detected when a lower sulfate to sodium ratio than in seawater is present in polar regions. This evidence can be masked when large amounts of non-sea-salt sulfate are present from other sources such as biogenic and anthropogenic sulfate. Frost flower δ34S values were measured for the first time in frost flower sulfates and did not differ significantly from the sea salt δ34S values of +21‰. A method using stable isotopes is introduced to determine the limit of contributions from sea salt and sea ice sources (including frost flowers and brine) on sulfate concentrations in aerosol samples from Alert, Canada. Knowledge of the range of values of δ34Snss and the SO4/Na ratio found in sea ice sources (i.e., frost flowers) is used to quantitatively constrain the contributions from frost flowers and sea salt in the Arctic aerosol mass during the onset of winter in 2007 and 2008, allowing for quantification of non-sea-salt sulfate amounts during times when frost flowers are present. Frost flower and/or brine influence was found predominantly in the coarse-mode aerosols (>0.95 μm). This method to determine the contributions from sea salt and sea ice sources can be carried over to future studies with snow and ice cores. Key Points Frost flower δ34S values measured for the first time Apportionment of frost flower, sea salt and NSS sulfate in Arctic aerosols Frost flower quantification for size segregated aerosols at Alert ©2014. American Geophysical Union. All Rights Reserved. Source

Reuten C.,RWDI AIR Inc. | Reuten C.,University of British Columbia | Dan Moore R.,University of British Columbia | Clarke G.K.,University of British Columbia
Journal of Applied Meteorology and Climatology | Year: 2011

In northwestern North America, which is a large area with complex physiography, Climatic Research Unit (CRU) Time Series, version 2.1, (TS 2.1) gridded monthly mean 2-m temperatures are systematically lower than interpolated monthly averaged North American Regional Reanalysis (NARR) pressure-level temperatures-in particular, in the winter. Quantification of these differences based on CRU gridded observations can be used to estimate pressure-level temperatures from CRU 2-m temperatures (1901-2002) that predate the NARR period (since 1979). Such twentieth-century pressure-level temperature fields can be used in glacier mass-balance modeling and as an alternative to calibrating general circulation model control runs, avoiding the need for accurate boundary layer parameterization. In this paper, an approach is presented that is transferable to moisture, wind, and other 3D fields with potential applications in wind power generation, ecology, and air quality. At each CRU grid point, the difference between CRU and NARR is regressed against seven predictors in CRU (mean temperature, daily temperature range, precipitation, vapor pressure, cloud cover, and number of wet and frost days) for the period of overlap between CRU and NARR (1979- 2002). Bayesian model averaging (BMA) is used to avoid overfitting the CRU-NARR differences and underestimating uncertainties. In cross validations, BMA provides reliable posterior predictions of the CRU- NARR differences and outperforms predictions from three alternative models: the constant model (24-yr mean), the regression model of highest Bayesian model probability, and the full model retaining all seven predictors in CRU. © 2011 American Meteorological Society. Source

Reuten C.,RWDI AIR Inc. | Reuten C.,University of British Columbia | Ainslie B.,University of British Columbia | Steyn D.G.,University of British Columbia | And 3 more authors.
Atmosphere - Ocean | Year: 2012

Assuming current emissions and background concentrations, we investigate how changes in synoptic meteorology alone affect ozone episodes in the Lower Fraser Valley, Canada, in future climates. We perform synoptic typing of combined sea level pressure and 500 hPa geopotential heights for June to September 1961- 2000 using the National Centers for Environmental Prediction (NCEP) reanalysis data. Five clusters provide a qualitatively good representation of typical synoptic conditions and stratify exceedance days into one cluster with more than half of all exceedances. Independent cluster analyses for climate model output from the Third Generation Coupled Global Climate Model (CGCM3.1 T63) 1961-2000 control runs and 2046-65 Special Report on Emissions Scenarios (SRES) A1B scenario runs give clusters qualitatively similar to those using NCEP data. When CGCM output is mapped to the NCEP clusters, the CGCM control run cluster frequencies are almost identical to NCEP frequencies, while CGCM 2046-65 output shows only small frequency changes. This indicates that, in future climates, the frequency of occurrence of synoptic types conducive to ozone exceedances will not be appreciably different than they are in the present climate. However, the CGCM predicts substantial increases in daily maximum temperatures in the Lower Fraser Valley across all five clusters. An analysis of exceedance probabilities suggests that the predicted temperature increase will more than double the number of exceedance days per year. Source

Arthurs D.,RWDI AIR Inc. | Ziada S.,McMaster University
Experiments in Fluids | Year: 2014

This article experimentally investigates the self-excited impinging planar jet flow, specifically the development and propagation of large-scale coherent flow structures convecting between the nozzle lip and the downstream impingement surface. The investigation uses phase-locked particle image velocimetry measurements and a new structure-tracking scheme to measure convection velocity and characterize the impingement mechanism near the plate, in order to develop a new feedback model that can be used to predict the oscillation frequency as a function of flow velocity (Uo), impingement distance (xo) and nozzle thickness (h). The resulting model prediction shows a good agreement with experimental tone frequency data. © 2014 Springer-Verlag Berlin Heidelberg. Source

Ainslie B.,University of British Columbia | Ainslie B.,Environment Canada | Steyn D.G.,University of British Columbia | Steyn D.G.,African Institute for Mathematical Sciences | And 3 more authors.
Atmosphere - Ocean | Year: 2013

A mechanistic exploration of how ozone formation in the Lower Fraser Valley (LFV) has changed over a 20-year (1985-2005) retrospective period was performed using numerical models, observations, and emissions data from four key episodes selected from the 20-year period. The motivation for this study was the observed differences in trends in summertime episodic ozone concentrations recorded at various monitoring stations within the valley; stations in the western part of the valley have generally shown a noticeable reduction in episodic ozone concentrations whereas stations in the eastern part of the valley have shown little or no improvement in their maximum 8-hour averaged ozone concentrations. Concurrent with these air quality changes, there has been a well-documented reduction in ozone precursor emissions along with an observed shift in the population patterns within the valley over the 20-year period. Ozone formation for four episodes, encompassing the different meteorological regimes that occur during LFV ozone events and spanning the retrospective period, were investigated using the Weather Research and Forecasting (WRF)-Sparse Matrix Operator Kernel Emission (SMOKE)-Community Multiscale Air Quality (CMAQ) modelling system. For each episode, two simulations, intended to isolate the effects of emission changes from meteorological changes, were performed: one with emissions set at the 1985 level and the other with emissions set at the 2005 level. Based on analysis of the model output, observational data, and precursor emission inventories, we find that the Port Moody station in the western LFV remains a volatile organic compound (VOC)-sensitive location; the central part of the LFV around the town of Chilliwack has generally changed from being VOC-limited to being NOx-limited; the easternmost part of the valley around the town of Hope has been and remains NOx-limited. Furthermore, based on the observational data and numerical model output, ozone production efficiency as a function of NO has increased noticeably at Chilliwack and likely in the other eastern parts of the valley. This efficiency increase has likely offset some of the benefits resulting from local NOx emission reductions. Source

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