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  • Authors: Sun, Q., F. Zwiers, X. Zhang and G. Li Publication Date: Jan 2020

    Trend scaling relationships between extreme precipitation and temperature are often used to represent the influence of long-term warming on the intensity of extreme precipitation. Indeed, such scaling relationships are often regarded as providing more reliable precipitation projections than direct projection, owing to higher confidence for temperature projections in model simulations. Due to limited data availability, especially for the sub-daily rainfall, so-called binning scaling relationships, which relate extreme precipitation to temperature at the time of occurrence and are estimated empirically either through a binning technique or quantile regression, have been considered as a substitute for trend scaling to project the long-term response of local extreme precipitation to temperature change (Lenderink and Van Meijgaard, 2008; Wasko and Sharma, 2014). Estimates of binning scaling rates are generally based on seasonal subdaily precipitation observations, and thus they are influenced by factors other than temperature that change systematically within a season, synchronously with the seasonal cycle (Zhang et al., 2017). In contrast to trend scaling, binning scaling often suggests faster than Clausius-Clapeyron intensification of sub-daily precipitation extremes with temperature.

    We explore this apparent contradiction between binning and trend scaling using a large ensemble of moderate resolution regional climate simulations for North America. The large amount of data that is available from this ensemble allows us to confidently estimate both trend and binning scaling rates for the climate that is simulated by that model. Specifically, we use a 35-member initial conditions ensemble of regional climate simulations produced with the Canadian CanRCM4 regional climate model for the period 1950-2100, with historical forcings for the period ending 2005 and RCP8.5 forcing subsequently. Each CanRCM4 ensemble member was driven by a corresponding member of a similar large ensemble of global simulations produced with the Canadian global Earth system model CanESM2 (Scinocca et al., 2016).

    We compare binning and trend scaling of precipitation extremes across different durations (1-hour, 3-hour, and 24-hour), considering annual and seasonal values, and both local and regional spatial scales. We provide strong evidence to clarify that binning scaling cannot project the long-term change in precipitation extreme, with substantial disagreement in the spatial pattern and magnitude of scaling rates between binning and trend scaling regardless of the duration, season, and spatial scale. Using the daily dew point temperature as scaling variable rather than dry air temperature does not eliminate the differences between binning and trend scaling rates. While shorter-duration extreme precipitation does appear to intensify faster with warming in CanRCM4, we only find super-adiabatic intensification of annual precipitation extremes in isolated regions regardless of accumulation durations. Compared with annual maximum results, winter extremes intensify more strongly over the western and southeastern North America across all timescales. A decreasing tendency of summer extremes is projected over the north and central Great Plains. The seasonal timing of the occurrences of precipitation extremes are expected to shift towards the cold season, reflecting the different changing tendencies in summer and winter extremes.

     

    Lenderink, G., and Van Meijgaard, E. 2008: Increase in hourly precipitation extremes beyond expectations from temperature changes. Nat. Geosci., 1, https://doi.org/10.1038/ngeo262.

    Scinocca, J. F., Kharin, V. V., Jiao, Y., Qian, M. W., Lazare, M., Solheim, L., and Flato. G. M., 2016: Coordinated Global and Regional Climate Modeling. J. Climate, 29, 17-35, https://doi.org/10.1175/Jcli-D-15-0161.1.

    Wasko, C., and Sharma, A. 2014: Quantile regression for investigating scaling of extreme precipitation with temperature. Water Resour. Res., 50, 3608-3614, https://doi.org/10.1002/2013WR015194.

    Zhang, X. B., Zwiers F. W., Li, G. L., Wan, H., Cannon, A. J., 2017: Complexity in estimating past and future extreme short-duration rainfall. Nat. Geosci., 10, 255-239, https://doi.org/10.1038/NGEO2911.

  • Authors: Wang, Y., C. Curry, C. Ballantyne, F. Anslow and F. Zwiers Publication Date: Dec 2019

    Analysis of extreme snow events is of great importance in many areas, including risk management and structural design. Severe natural hazards in the mountain regions, such as avalanche, are largely due to heavy snowfall events and seasonally evolving snow-pack. Moreover, guidelines for infrastructure design should include estimates of maximum snow load, not only historically but also as projected under future climate change.

    In this work, we compute annual maximum time series from daily snow depth and snow water equivalent (SWE) data at over 2000 meteorological stations across Canada from 1939- 2016. The more extensive snow depth results are converted to snow loads by applying a suitable density curve that empirically relates extreme snow depth to extreme snow load. An extreme value analysis of the latter is then conducted using the generalized extreme value (GEV) distribution, providing a description of the heavy tail behaviour of the historical snow load. Finally, return values of annual snow load are computed for a range of return periods and compared to previous estimates from the 2015 edition of the National Building Code of Canada.

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

    Understanding how human influences are affecting different parts of the climate system allows us to improve future climate projections. Due to the relative sparsity of precipitation data and the large amount of internal variability that it exhibits, detecting and attributing the human influence on precipitation is difficult. This Science Brief covers recent research that uses information about the physical processes responsible for precipitation in order to detect the anthropogenic influence on winter precipitation over North America and Eurasia over the 1920-2015 period.

    Publishing in Geophysical Research Letters, Guo et al. (2019) use a technique known as "dynamical adjustment," to estimate the atmospheric circulation and thermodynamic contributions to observed precipitation over Eastern North America and Northern Eurasia over the 1920-2015 period. They find that the thermodynamic component, due to anthropogenic emissions, contributes to increases in precipitation in both regions. They then compare the spatial pattern and magnitude of these components to those obtained from global climate models driven with anthropogenic forcings. They find strong agreement between the thermodynamic components of precipitation obtained from the observational data and those obtained from climate model output.

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

    The October 2019 edition of the PCIC Update newsletter contains stories on: new adaptation reports for the Kootenay and Boundary, and Bulkley Nechako and Fraser-Fort George regions; work on PCIC's online tools; a co-produced report on the Cowichan Valley which was featured in the media; the new Gridded Hydrologic Model Output Data Portal page; the new video series on climate change and BC agriculture; ClimateData.ca going live and PCIC research to support salmon conservation. The newsletter also has a staff profile on Kari Tyler and covers the Pacific Climate Seminar Series, staff changes at PCIC and recent PCIC publications.

  • Authors: The BC Agriculture & Food Climate Action Initiative Publication Date: Aug 2019

    Bulkley-Nechako & Fraser-Fort George Adaptation Strategies plan is the eighth regional plan developed as part of the Regional Adaptation Program delivered by the BC Agriculture & Food Climate Action Initiative. The report contains a distinctive set of local sector impacts and priorities, as well as a series of strategies and actions for adapting and strengthening resilience. The plans are intended to offer clear actions suited to the specifics of the local context, both with respect to anticipated changes and local capacity and assets.

  • Authors: The Fraser Basin Council Publication Date: Aug 2019

    Climate change is challenging industry and communities across the Northeast region of the province. Wildfires, hail storms, and floods have already challenged local infrastructure and posed health risks to communities. Projected climate change for the region includes increases in frequency and intensity of extremes. Ensuring the region is as prepared as possible for future climate events is critical to maintaining a thriving community, robust natural environment, and vibrant economy. As prepared as possible means the region understands how the climate is changing, and is working together to increase resiliency, and to improve natural and physical infrastructure. Early efforts will reduce the reliance on emergency management and support the ability to thrive over time. Local governments in the region are taking a proactive approach to understanding how climate change will pose risks to Northeast communities and are planning together to build resiliency across the region.

    This document is intended to offer science-based information on how the Northeast’s climate is changing and expected to change over the 21st century. Designing to current and future climate parameters is anticipated to be markedly more cost effective than reacting to climate shocks and stresses over time. In the report, climate projections for the 2020s are offered to represent current climate conditions; projections for the 2050s illustrate the trajectory of change regardless of global emissions reductions; and projections for the 2080s illustrate our likely “business as usual” future climate scenario by late century. The 2020s projections are useful as they more accurately depict the current state of climate than historical observed baseline data. The 2050s projections are useful for medium-term planning and infrastructure purposes, while the 2080s provide guidance for long-term infrastructure decisions.

  • Authors: The BC Agriculture & Food Climate Action Initiative Publication Date: Jul 2019

    The Kootenay & Boundary Regional Adaptation Strategies plan is the seventh regional plan developed as part of the Regional Adaptation Program delivered by the BC Agriculture & Food Climate Action Initiative. The report contains a distinctive set of local sector impacts and priorities, as well as a series of strategies and actions for adapting and strengthening resilience. The plans are intended to offer clear actions suited to the specifics of the local context, both with respect to anticipated changes and local capacity and assets.

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

    Presentation for the Private Forest Landowners Association Annual Conference.

  • Source Publication: Geophysical Research Letters, doi:10.1029/2019GL082908. Authors: Li, C., F. Zwiers, X. Zhang, G. Chen, J. Lu, G. Li, J. Norris, Y. Tan, Y. Sun and M. Liu Publication Date: Jun 2019

    Climate models project that extreme precipitation events will intensify in proportion to their intensity during the 21st century at large spatial scales. The identification of the causes of this phenomenon nevertheless remains tenuous. Using a large ensemble of North American regional climate simulations, we show that the more rapid intensification of more extreme events also appears as a robust feature at finer regional scales. The larger increases in more extreme events than in less extreme events are found to be primarily due to atmospheric circulation changes. Thermodynamically induced changes have relatively uniform effects across extreme events and regions. In contrast, circulation changes weaken moderate events over western interior regions of North America, and enhance them elsewhere. The weakening effect decreases and even reverses for more extreme events, whereas there is further intensification over other parts of North America, creating an “intense gets intenser” pattern over most of the continent.

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

    PCIC's June 2019 newsletter covers the following stories: the Climate Report for Vancouver Coastal Health, the Regional Assessment for Northeastern BC and PCIC's Co-Produced report on the Cowichan Valley featured in the media. The newsletter also contains a staff profile on Dr. Whitney Huang, covers Dr. William Hsieh's lecture for the Pacific Climate Seminar Series and includes a story on the most recent Science Brief, on temperature and precipitation indices for Canada, in addition to staff changes and PCIC's peer-reviewed publications.

  • 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.

  • Authors: Lower Mainland Facilities Management, Pinna Sustainability, The Pacific Climate Impacts Consortium Publication Date: May 2019

    Rising temperatures, shifting precipitation patterns, and extreme weather events are already affecting Vancouver Coastal Health (VCH) and our Communities of Care. Chronic stresses and acute shocks are creating a “new climate reality” for health facilities and service delivery, and reshaping our working context.

    With this series of reports, Lower Mainland Facilities Management (LMFM) demonstrates forward-thinking public sector leadership; positions health authorities to meet legislated requirements for addressing climate risk and reducing emissions; and, enables major infrastructure projects to assess climate resilience.

  • 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, 11, 5, doi:10.1029/2018MS001532. Authors: He. Y., N. McFarlane and A. H. Monahan Publication Date: Mar 2019

    This paper presents a new mathematical formulation to account for the effects turbulent motions in comprehensive global climate models. The new formulation is based on recently published theoretical advances and results of high‐resolution numerical model simulations for specialized atmospheric turbulence regimes. The new formulation is tested and evaluated using a simplified model configuration designed to represent a single grid volume of a global climate model.

  • 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: 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.

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