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  • Authors: Murdock, T. Publication Date: Jun 2019

    Presentation for the Private Forest Landowners Association Annual Conference.

  • Authors: The Pacific Climate Impacts Consortium Publication Date: Jun 2019

    As Canada's climate continues to change, trends in mean temperature and precipitation are evident, but so to are trends in indices based on temperature and precipitation observations. These are of interest to a wide range of sectors and this Science Brief covers a recent paper on changes to these indices in Canada.

  • Source Publication: Journal of Climate, early online access, doi: 10.1175/JCLI-D-18- 0461.1. Authors: Seiler, C., Publication Date: Apr 2019

    Extratropical cyclones (ETCs) are known to intensify due to three vertically interacting positive potential vorticity perturbations that are associated with potential temperature anomalies close to the surface (θB), condensational heating in the lower-level atmosphere (qsat), and stratospheric intrusion in the upper-level atmosphere (qtr). This study presents the first climatological assessment of how much each of these three mechanisms contributes to the intensity of extreme ETCs. Using relative vorticity at 850 hPa as a measure of ETC intensity, results show that in about half of all cases the largest contributions during maximum ETC intensity are associated with qsat (53% of all ETCs), followed by qtr (36%) and θB (11%). The relative frequency of storms that are dominated by qsat is higher 1) during warmer months (61% of all ETCs during warmer months) compared to colder months (50%) and 2) in the Pacific (56% of all ETCs in the Pacific) compared to the Atlantic (46%). The relative frequency of ETCs that are dominated by θB is larger 1) during colder months (13%) compared to warmer months (3%), 2) in the Atlantic (15%) compared to the Pacific (8%), and 3) in western (11%–20%) compared to eastern ocean basins (4%–9%). These findings are based on piecewise potential vorticity inversion conducted for intense ETCs that occurred from 1980 to 2016 in the Northern Hemisphere (3273 events; top 7%). The results may serve as a baseline for evaluating ETC biases and uncertainties in global climate models.

  • Authors: British Columbia Ministry of Environment and Climate Change Strategy Publication Date: Apr 2019

    A forward-thinking group at Nanaimo Hospital developed a comprehensive climate risk assessment matrix which is becoming an integral part of their organizational decision-making. Future hospital retrofits will potentially include increased cooling capacity, enhanced air filtration, and other measures to reduce costs, greenhouse gas emissions, and protect the facility and its patients from the potential effects of climate change.

  • Source Publication: Journal of Advances in Modeling Earth Systems, doi: 10.1029/2018MS001532. Authors: He, Y., N.A.McFarlane, and A.H. Monahan Publication Date: Mar 2019

    A new semi‐empirical turbulence parameterization is presented. Key features of the scheme include representation of turbulent diffusivities in terms of the turbulent kinetic energy (TKE) which is determined by solving a quasi‐equilibrium form of the equation representing the TKE budget. The new parameterization is innovative in the treatment of turbulent transfer in stably stratified conditions and the representation of non‐local contributions to the vertical transport of heat, moisture, and scalar prognostic variables in convectively active boundary layers. A key element in the modeling of turbulence in stably stratified conditions is the formulation of the turbulent Prandtl number based on results of recently published theoretical, modeling and observational studies of stratified turbulence in the atmospheric boundary layer. The new parameterization has been implemented in the CanAM4 single column model. Its performance in comparison with that of the operational CanAM4 turbulence parameterization is documented in terms of selected results from case studies for clear sky conditions based on meteorological observations from the KNMI‐mast at Cabauw, Netherlands, and the DYCOMS II case study of stratocumulus‐topped marine boundary layers. The performance of the new and operational schemes is qualitatively similar in clear sky conditions in both convective and stable boundary layer regimes. However, they perform differently for the extended simulations for the DYCOM‐II case study. The new scheme maintains an elevated stratocumulus layer throughout a 30‐hour simulation but peak liquid water contents are larger than LES simulations.

  • Authors: The Pacific Climate Impacts Consortium Publication Date: Mar 2019

    This edition of the PCIC Update covers work on modelling Fraser River streamflow temperatures, recently published wildfire research, the release of the PCIC Climate Explorer tool (PCEX), a new collaboration between the Canadian Centre for Climate Services and PCIC, recent research in precipitation extremes, work on incorporating the findings of climate science into engineering design, a staff profile on Yaqiong Wang, the release of the 2017-2018 Corporate Report, as well as the latest Science Brief, staff changes, recent publications and the ongoing Pacific Climate Seminar Series.

  • Authors: The Pacific Climate Impacts Consortium Publication Date: Feb 2019

    Real-time precipitation data can be of use to areas ranging from forecasting to forest fire management. This Science Brief covers a recent paper that examines the past ten years of a near real-time Canadian precipitation product.

    Writing in Atmosphere-Ocean, Fortin et al. (2018) examine the Canadian Precipitation Analysis (CaPA), a near real-time precipitation product covering all of North America that is produced by Environment and Climate Change Canada. They review papers that evaluate CaPA compared to precipitation observations as well as the applications of CaPA for various types of research, ranging from hydrology1 and hydrometeorology2 to biogeophysics3. They find that CaPA compares favourably against other precipitation data, and report that it has been used successfully in studies across a number of fields, including hydrometeorology, hydrology, land surface and atmospheric modelling.

  • Source Publication: Hydrology and Earth System Sciences, 23, 811-828, doi:10.5194/hess-23-811-2019. Authors: Islam, S. Ul, C.L. Curry, S.J. Dery and F.W. Zwiers Publication Date: Feb 2019

    In response to ongoing and future-projected global warming, mid-latitude, nival river basins are expected to transition from a snowmelt-dominated flow regime to a nival–pluvial one with an earlier spring freshet of reduced magnitude. There is, however, a rich variation in responses that depends on factors such as the topographic complexity of the basin and the strength of maritime influences. We illustrate the potential effects of a strong maritime influence by studying future changes in cold season flow variability in the Fraser River Basin (FRB) of British Columbia, a large extratropical watershed extending from the Rocky Mountains to the Pacific Coast. We use a process-based hydrological model driven by an ensemble of 21 statistically downscaled simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5), following the Representative Concentration Pathway 8.5 (RCP 8.5).

    Warming under RCP 8.5 leads to reduced winter snowfall, shortening the average snow accumulation season by about one-third. Despite this, large increases in cold season rainfall lead to unprecedented cold season peak flows and increased overall runoff variability in the VIC simulations. Increased cold season rainfall is shown to be the dominant climatic driver in the Coast Mountains, contributing 60 % to mean cold season runoff changes in the 2080s. Cold season runoff at the outlet of the basin increases by 70 % by the 2080s, and its interannual variability more than doubles when compared to the 1990s, suggesting substantial challenges for operational flow forecasting in the region. Furthermore, almost half of the basin (45 %) transitions from a snow-dominated runoff regime in the 1990s to a primarily rain-dominated regime in the 2080s, according to a snowmelt pulse detection algorithm. While these projections are consistent with the anticipated transition from a nival to a nival–pluvial hydrologic regime, the marked increase in FRB cold season runoff is likely linked to more frequent landfalling atmospheric rivers in the region projected in the CMIP5 models, providing insights for other maritime-influenced extratropical basins.

  • Source Publication: Scientific Data, 6, 180299, doi:10.1038/sdata.2018.299 Authors: Werner, A.T., M.S. Schnorbus, R.R. Shrestha, A.J. Cannon, F.W. Zwiers, G. Dayon and F. Anslow, Publication Date: Jan 2019

    We describe a spatially contiguous, temporally consistent high-resolution gridded daily meteorological dataset for northwestern North America. This >4 million km2 region has high topographic relief, seasonal snowpack, permafrost and glaciers, crosses multiple jurisdictional boundaries and contains the entire Yukon, Mackenzie, Saskatchewan, Fraser and Columbia drainages. We interpolate daily station data to 1/16° spatial resolution using a high-resolution monthly 1971–2000 climatology as a predictor in a thin-plate spline interpolating algorithm. Only temporally consistent climate stations with at least 40 years of record are included. Our approach is designed to produce a dataset well suited for driving hydrological models and training statistical downscaling schemes. We compare our results to two commonly used datasets and show improved performance for climate means, extremes and variability. When used to drive a hydrologic model, our dataset also outperforms these datasets for runoff ratios and streamflow trends in several, high elevation, sub-basins of the Fraser River.

  • Source Publication: Nature Scientific Data, 6, 180299, doi:10.1038/sdata.2018.299. Authors: Werner, A.T., R.R. Shrestha, A.J. Cannon, M.S. Schnorbus, F.W. Zwiers, G. Dayon and F. Anslow Publication Date: Jan 2019

    We describe a spatially contiguous, temporally consistent high-resolution gridded daily meteorological dataset for northwestern North America. This >4 million km2 region has high topographic relief, seasonal snowpack, permafrost and glaciers, crosses multiple jurisdictional boundaries and contains the entire Yukon, Mackenzie, Saskatchewan, Fraser and Columbia drainages. We interpolate daily station data to 1/16° spatial resolution using a high-resolution monthly 1971–2000 climatology as a predictor in a thin-plate spline interpolating algorithm. Only temporally consistent climate stations with at least 40 years of record are included. Our approach is designed to produce a dataset well suited for driving hydrological models and training statistical downscaling schemes. We compare our results to two commonly used datasets and show improved performance for climate means, extremes and variability. When used to drive a hydrologic model, our dataset also outperforms these datasets for runoff ratios and streamflow trends in several, high elevation, sub-basins of the Fraser River.

  • Source Publication: Geophysical Research Letters, 46, 1651-1661, doi:10.1029/2018GL080720. Authors: Curry, C.L., S.U. Islam, F.W. Zwiers and S.J. Dery Publication Date: Jan 2019

    Snow‐dominated watersheds are bellwethers of climate change. Hydroclimate projections in such basins often find reductions in annual peak runoff due to decreased snowpack under global warming. British Columbia's Fraser River Basin (FRB) is a large, nival basin with exposure to moisture‐laden atmospheric rivers originating in the Pacific Ocean. Landfalling atmospheric rivers over the region in winter are projected to increase in both strength and frequency in Coupled Model Intercomparison Project Phase 5 climate models. We investigate future changes in hydrology and annual peak daily streamflow in the FRB using a hydrologic model driven by a bias‐corrected Coupled Model Intercomparison Project Phase 5 ensemble. Under Representative Concentration Pathway (8.5), the FRB evolves toward a nival‐pluvial regime featuring an increasing association of extreme rainfall with annual peak daily flow, a doubling in cold season peak discharge, and a decrease in the return period of the largest historical flow, from a 1‐in‐200‐year to 1‐in‐50‐year event by the late 21st century.

  • Source Publication: Earth's Future, doi:10.1029/2018EF001001. Authors: Li, C., F.W. Zwiers, X. Zhang and G. Li Publication Date: Jan 2019

    Global warming is expected to increase the amount of atmospheric moisture, resulting in heavier extreme precipitation. Various studies have used the historical relationship between extreme precipitation and temperature (temperature scaling) to provide guidance about precipitation extremes in a future warmer climate. Here we assess how much information is required to robustly identify temperature scaling relationships, and whether these relationships are equally effective at different times in the future in estimating precipitation extremes everywhere across North America. Using a large ensemble of 35 North American regional climate simulations of the period 1951–2100, we show that individual climate simulations of length comparable to that of typical instrumental records are unable to constrain temperature scaling relationships well enough to reliably estimate future extremes of local precipitation accumulation for hourly to daily durations in the model's climate. Hence, temperature scaling relationships estimated from the limited historical observations are unlikely to be able to provide reliable guidance for future adaptation planning at local spatial scales. In contrast, well‐constrained temperature scaling relations based on multiple regional climate simulations do provide a feasible basis for accurately projecting precipitation extremes of hourly to daily durations in different future periods over more than 90% of the North American land area.

  • Source Publication: Hydrological Processes, doi: 10.1002/hyp.13321. Authors: Tsuruta, K., M.A. Hassan, S.D. Donner and Y. Alila, Publication Date: Jan 2019

    Future sediment dynamics may be affected by changing climates or hydrological regimes because of the close link between hydrology and sediment erosion, deposition, and transport. Previously, investigations of these potential changes have been constrained by a combination of limited observational data, hydrological drivers, and appropriate mechanistic models. Additionally, there is often ambiguity regarding how to disentangle the impacts of climate and hydrology from direct human factors such as reservoirs and land‐use change, which often exert more control over sediment dynamics. In this study, we utilize a recently developed, large‐scale, distributed, mechanistic sediment transport model to project future sediment erosion, deposition, and transportation within the Fraser River Basin in British Columbia, Canada—a basin with historical water flux and sediment load observations and limited anthropogenic influences upstream of its delta. The sediment model is driven by synthetic land‐surface hydrology derived from Scenarios A1B, A2, and B1 of the Special Report on Emissions Scenarios, which were provided by the Pacific Climate Impacts Consortium. Resulting simulations of water flux and sediment load from 1965 to 1994 are first validated against observational data then compared with future projections. Future projections show an overall increase in annual hillslope erosion and in‐channel transportation, a shift towards earlier spring peak erosion and transportation, and longer persistence of the sediment signal through the year. These shifts in timing and annual yield may have deleterious effects on spawning sockeye salmon and are insufficient to counteract future coastal retreat caused by sea‐level rise.

  • Source Publication: Earth's Future, doi:10.1029/2018EF001050. Authors: M.C. Kirchmeier‐Young N.P. Gillett F.W. Zwiers A.J. Cannon F.S. Anslow Publication Date: Dec 2018

    A record 1.2 million ha burned in British Columbia, Canada's extreme wildfire season of 2017. Key factors in this unprecedented event were the extreme warm and dry conditions that prevailed at the time, which are also reflected in extreme fire weather and behavior metrics. Using an event attribution method and a large ensemble of regional climate model simulations, we show that the risk factors affecting the event, and the area burned itself, were made substantially greater by anthropogenic climate change. We show over 95% of the probability for the observed maximum temperature anomalies is due to anthropogenic factors, that the event's high fire weather/behavior metrics were made 2–4 times more likely, and that anthropogenic climate change increased the area burned by a factor of 7–11. This profound influence of climate change on forest fire extremes in British Columbia, which is likely reflected in other regions and expected to intensify in the future, will require increasing attention in forest management, public health, and infrastructure.

  • Authors: The Pacific Climate Impacts Consortium Publication Date: Dec 2018

    This is the Pacific Climate Impacts Consortium's 2017-2018 Corporate Report.

  • Source Publication: Earth's Future, doi:10.1029/2018EF001001. Authors: Li, C., F. Zwiers X. Zhang and G. Li Publication Date: Dec 2018

    Global warming is expected to increase the amount of atmospheric moisture, resulting in heavier extreme precipitation. Various studies have used the historical relationship between extreme precipitation and temperature (temperature scaling) to provide guidance about precipitation extremes in a future warmer climate. Here we assess how much information is required to robustly identify temperature scaling relationships, and whether these relationships are equally effective at different times in the future in estimating precipitation extremes everywhere across North America. Using a large ensemble of 35 North American regional climate simulations of the period 1951–2100, we show that individual climate simulations of length comparable to that of typical instrumental records are unable to constrain temperature scaling relationships well enough to reliably estimate future extremes of local precipitation accumulation for hourly to daily durations in the model's climate. Hence, temperature scaling relationships estimated from the limited historical observations are unlikely to be able to provide reliable guidance for future adaptation planning at local spatial scales. In contrast, well‐constrained temperature scaling relations based on multiple regional climate simulations do provide a feasible basis for accurately projecting precipitation extremes of hourly to daily durations in different future periods over more than 90% of the North American land area.

  • Authors: Zwiers, F., C. Li, X. Zhang and G. Li Publication Date: Dec 2018

    Poster presented at 2018 AGU Fall Meeting, Dec. 10th-14th in Washington, DC.

  • Authors: Murdock, T. Publication Date: Nov 2018

    Presentation for Getting Climate Ready – Adaptation Tools for Northwest Communities, in Terrace, BC on 29 November 2018.

  • Authors: The Pacific Climate Impacts Consortium Publication Date: Oct 2018

    This newsletter discusses the IPCC's Special Report on a global warming of 1.5 °C, the summer of 2018 in BC, supporting agriculture in the Fraser Valley, PCIC's new Seasonal Maps Portal, Columbia Basin Trust workshops and Dr. Jana Sillmann's visit. The newsletter also has a staff spotlight on Matthew Benstead, covers talks delivered by Drs. Jana Sillmann and Whitney Huang, the most recent PCIC Science Brief on Paris Accord emissions and temperature limits, as well as PCIC publications and staff changes.

  • Source Publication: Journal of Climate, 31, 19, 7771-7787, doi:10.1175/JCLI-D-17-0552.1 Authors: Mueller, B.L., N.P. Gillett, A. Monahan and F.W. Zwiers Publication Date: Sep 2018

    The paper presents results from a climate change detection and attribution study on the decline of Arctic sea ice extent in September for the 1953–2012 period. For this period three independently derived observational datasets and simulations from multiple climate models are available to attribute observed changes in the sea ice extent to known climate forcings. Here we direct our attention to the combined cooling effect from other anthropogenic forcing agents (mainly aerosols), which has potentially masked a fraction of greenhouse gas–induced Arctic sea ice decline. The presented detection and attribution framework consists of a regression model, namely, regularized optimal fingerprinting, where observations are regressed onto model-simulated climate response patterns (i.e., fingerprints). We show that fingerprints from greenhouse gas, natural, and other anthropogenic forcings are detected in the three observed records of Arctic sea ice extent. Beyond that, our findings indicate that for the 1953–2012 period roughly 23% of the greenhouse gas–induced negative sea ice trend has been offset by a weak positive sea ice trend attributable to other anthropogenic forcing. We show that our detection and attribution results remain robust in the presence of emerging nonstationary internal climate variability acting upon sea ice using a perfect model experiment and data from two large ensembles of climate simulations.

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