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ABSTRACT: Parallel daily temperature observations at site pairs over a 5‐year period at 88 locations across Canada were used to derive and validate adjustments required during homogenization process. The data was first ‘aligned’ for compatible observing times at 12 locations (other locations do not have this problem). Then the homogenization adjustments were obtained using three procedures (Seasonal Bias, Monthly Interpolation and Quantile Matching) and two approaches (using parallel and neighbours observations). The root mean squared error (RMSE) between the daily temperatures of site 1 and site 2, and the percentage of days within 0.5 °C (PD05) between site 1 and site 2 were used to assess the uncertainty in the mean and extreme values, respectively. The instruments were not necessarily collocated as the distance between the two observing sites varied from 0 to 30 km. The results confirm that it is necessary to apply adjustments for known issues first, such as a different observing time. They also show that when a shift between site 1 and site 2 (defined by the annual mean of the daily temperature differences) is small [<0.25 standard deviation (SD)], the adjustments do not reduce the error between site 1 and site 2. When the shift size is between 0.25 and 0.5 SD, the adjustments derived from parallel observations help to reduce the uncertainty. When the shift is large (>0.5 SD), both approaches reduce the error, although the adjustments derived from parallel observations provide better results as compared to those computed from neighbour observations. The results also indicate that Quantile Matching adjustments can provide a better estimate of the adjustments than the other methods evaluated to indices of extreme temperature computed from the adjusted daily values; however, highly correlated neighbours are needed when the adjustments are based on neighbours observations. [ABSTRACT FROM AUTHOR]

In this study, high‐resolution projections of temperature and precipitation changes over Canada were developed through the Providing Regional Climates for Impact Studies (PRECIS) model under Representative Concentration Pathways (RCPs). In detail, the PRECIS model was employed to conduct simulations for the historical period over the entirety of Canada, driven by the boundary conditions from both ERA‐Interim (1979–2011) and HadGEM2‐ES (1959–2005). The performance of PRECIS simulations in reproducing historical climatology of Canada was then validated through comparison with observed temperature and precipitation over the baseline period (1986–2005). The boundary conditions from HadGEM2‐ES under RCP4.5 and RCP8.5 was used to drive PRECIS for simulating climatic variables over Canada for the period of 2006–2099. Future climate projections of temperature and precipitation as well as their extreme indices over two time‐slices (i.e. 2046–2065 and 2076–2095) were extracted and analysed. The results could help investigate how the regional climate over Canada will respond to global warming as well as the spatio‐temporal characteristics of plausible climate changes in the Canadian context. The validation results demonstrate that the PRECIS model is effective in reproducing the historical climatological patterns of annual mean temperature and total precipitation across Canada. Projections of temperature and precipitation for the two future periods indicate that there will be an apparent increasing pattern over Canada. The projected changes derived in this study can provide decision‐makers with valuable information to evaluate possible impacts on economic, social and environmental sectors at regional and local scales. [ABSTRACT FROM AUTHOR]

This study tests various applications of a new technique for infilling sparse monthly climate data which combines temperature anomalies from gridded observational and reanalysis data sets with baseline climatologies from short-instrumental records. Out-of-sample comparisons between infilled and observed climate data for 53 stations in northeastern Canada suggests that mean absolute errors using the proposed method are ±1 and ±0.5 °C on monthly and annual timescales, respectively. Evaluation of several gridded data sets used to guide infilling suggests that ERA-Interim ( ERAI) and modern-era retrospective reanalysis ( MERRA) reanalyses are the most suitable for this purpose in the Labrador-Ungava region. [ABSTRACT FROM AUTHOR]

Minor changes to seasonal air temperature and precipitation can have a substantial impact on the availability of water resources within large watersheds. Two such watersheds, the north-flowing Mackenzie and east-flowing Saskatchewan Basins, have been identified as highly vulnerable to such changes and, therefore, selected for study as part of the Climatic Redistribution of western Canadian Water Resources project. This project aims to evaluate spatial and temporal changes to water resource distribution through the analysis of a suite of hydroclimatic and streamflow variables. As part of this analysis, dominant summer (May-October) circulation patterns at 500 hPa for 1950-2011 are identified using the method of self-organizing maps. Surface climate variables associated with these patterns are then identified, including both daily air temperature and precipitation and seasonal Standardized Precipitation Evapotranspiration Index values. Statistical methods are applied to assess the relationships between dominant circulation patterns and the Southern Oscillation Index (SOI) and Pacific Decadal Oscillation (PDO). Results indicate that mid-summer (July-August) is dominated by a split-flow blocking pattern, resulting in cool (warm), wet (dry) conditions in the southern (northern) portion of the study area. By contrast, the shoulder season (May and October) is dominated by a trough of low pressure over the North Pacific Ocean. The frequency of weak split-flow blocking is higher during positive SOI and negative PDO, whereas ridging over the western continent is more frequent during negative SOI and positive PDO. Results from this analysis increase our knowledge of processes, controlling the distribution of summer water resources in western Canada. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We present a new 23-site network of white spruce ring-width chronologies near boreal treeline in Old Crow Flats, Yukon Territory, Canada. Most chronologies span the last 300 years and some reach the mid-16th century. The chronologies exhibit coherent growth patterns before the 1930s. However, since the 1930s, they diverge in trend and exhibit one of two contrasting, but well-replicated patterns we call Group 1 and Group 2. Over the instrumental period (1930-2007) Group 1 sites were inversely correlated with previous-year July temperatures while Group 2 sites were positively correlated with growth-year June temperatures. At the broader northwestern North America ( NWNA) scale, we find that the Group 1 and Group 2 patterns are common to a number of white spruce chronologies, which we call NWNA 1 and NWNA 2 chronologies. The NWNA 1 and NWNA 2 chronologies also share a single coherent growth pattern prior to their divergence (ca. 1950s). Comparison of the NWNA 1/ NWNA 2 chronologies against gridded 20th-century temperatures for NWNA and reconstructed northern hemisphere summer temperatures ( ad 1300-2000) indicates that all sites responded positively to temperature prior to the mid-20th century (at least back to ad 1300), but that some changed to a negative response ( NWNA 1) while others maintained a positive response ( NWNA 2). The spatial extent of divergence implies a large-scale forcing. As the divergence appears to be restricted to the 20th century, we suggest that the temperature response shift represents a moisture stress caused by an anomalously warm, dry 20th-century climate in NWNA, as indicated by paleoclimatic records. However, because some sites do not diverge and are located within a few kilometres of divergent sites, we speculate that site-level factors have been important in determining the susceptibility of sites to the large-scale drivers of divergence. [ABSTRACT FROM AUTHOR]

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Stochastic weather generators are widely used for developing local climate scenarios from large-scale climate change scenarios simulated by GCMs. We used AAFC-WG, a stochastic weather generator developed at Agriculture and Agri-Food Canada (AAFC), to develop daily climate scenarios for the time period 2040 2069 for the agricultural regions of Canada, based on 4 climate change simulations conducted by global climate models CGCM3, HadCM3, ECHAMS/MPI-OM and CSIRO-Mk3.5. Annual and growing season (1 May to 30 September) extreme daily values of maximum temperature, minimum temperature and precipitation were estimated from these scenarios on fine grids (0.5° latitude x 0.5° longitude) and from direct daily global climate model (GCM) outputs on coarse grids (~2.8° latitude x 2.8° longitude for CGCM3, 2.5° latitude x 3.75° longitude for HadCM3, and ~1.865° latitude x 1.875° longitude for ECHAMS/MPI-OM and CSIRO-Mk3.5). Compared with the corresponding values from direct GCM outputs, the extremes from daily climate scenarios generated by the AAFC-WG provided more detail at the finer spatial scale. Although the spatial patterns of the changes in climate extremes were often similar, actual values of the extremes from localized scenarios may be more reliable than those from direct GCM outputs since climate extremes under the present climate were not often realistically reproduced by the GCMs studied here. It is understood that the actual values are important as they provide the basis for climate change impact studies and the development of adaptation strategies, [ABSTRACT FROM AUTHOR]

The article discusses several essential climate variables (ECVs) that serve as time series of major climatic indicators. It mentions that ECVs, which include air temperature, air pressure and ocean surfacek, are constantly and fully monitored. It offers information on the ECVs in different parts of the world including Alaska, Canada and Asia.

On 1 July 1961, the climatological day was redefined to end at 0600 UTC (coordinated universal time) at all synoptic (airport) stations in Canada. Prior to that, the climatological day ended at 1200 UTC for maximum temperature and 0000 UTC for minimum temperature. This study shows that the redefinition of the climatological day in 1961 has created a cold bias in the annual and seasonal means of daily minimum temperatures across the country while the means of daily maximum temperatures were not affected. Hourly temperatures taken at 121 stations for 1953–2007 are used to determine the magnitude of the bias and its spatial variation. It was found that the bias is more pronounced in the eastern regions; its annual mean varies from -0.2° in the west to -0.8°C in the east. Not all days are affected by this change in observing time, and the annual percentage of affected days ranges from 15% for locations in the west to 38% for locations in the east. An approach based on hourly values is proposed for adjusting the affected daily minimum temperatures over 1961–2007. The adjustment on any individual day varies from 0.5° to 12.5°C. The impact of the adjustment is assessed by examining the trends in the annual mean of the daily minimum temperatures for 1950–2007. Overall, with the adjustment, the trends are becoming either more positive or are reversing from negative to positive, and they have changed by as much as 1°C in numerous locations in the eastern regions. [ABSTRACT FROM AUTHOR]

The article highlights the weather conditions for April 2008 in the U.S., Alaska and Canada. The author stated that wet conditions persisted in most areas from eastern Plains to the Mississippi Valley with below-normal temperatures. Meanwhile, precipitation in Alaska is above normal with two to six times greater than normal. On the other hand, snow in Canada is not so remarkable and the eastern part has a reprieve from snowstorms.

Annual and seasonal trends in temperature, dewpoint, relative humidity, and specific humidity are presented for the period 1953–2005. The analysis uses hourly observations from 75 climatological stations across Canada. Data were examined for discontinuities due to changes in instruments and observing practice. It was found that the main discontinuity corresponds to the replacement of the psychrometer by the dewcel in the early 1970s, which created an artificial negative step in relative humidity and dewpoint at many locations. After accounting for these discontinuities, the results of trend analysis show evidence of an increase in air moisture content associated with the warming observed in the country. During winter and spring, the significant warming in the western and southern regions is accompanied by an increase in dewpoint and specific humidity and by a decrease in relative humidity; in summer, warming is observed in the southeast and it is associated with significant positive trends in dewpoint and specific humidity. Although there is no strong evidence of a greater nighttime warming in Canada over 1953–2005, the nighttime dewpoint and specific humidity trends are slightly larger than the daytime trends, especially during the spring and summer. [ABSTRACT FROM AUTHOR]

Nonlinear projections of the Arctic Oscillation (AO) index onto North American winter (December–March) 500-mb geopotential height (Z500) and surface air temperature (SAT) anomalies reveal a pronounced asymmetry in the atmospheric patterns associated with positive and negative phases of the AO. In a linear view, the Z500 anomaly field associated with positive AO resembles a positive North Atlantic Oscillation pattern with statistically significant positive and negative anomalies stretching zonally into central-eastern USA and Canada, respectively, resulting in a cold climate anomaly over northeastern and eastern Canada, Alaska and the west coast of USA, and a warm climate anomaly over the rest of the continent. By contrast, the nonlinear behavior, mainly a quadratic association with AO, which is most apparent when the amplitude of the AO index is large, has the same spatial pattern and sign for both positive and negative values of the index. The nonlinear pattern reveals negative Z500 anomalies over the west coast of USA and the North Atlantic and positive Z500 anomalies at higher latitudes centered over the Gulf of Alaska and northeastern Canada accompanied by cooler than normal climate over the USA and southwestern Canada and warmer than normal climate over other regions of the continent. A similar analysis is conducted on the data from the Canadian Center for Climate Modelling and Analysis second generation coupled general circulation model. The nonlinear patterns of North American Z500 and SAT anomalies associated with the AO in the model simulation are generally consistent with the observational results, thereby confirming the robustness of the nonlinear behavior of North American winter climate with respect to the AO in a climate simulation that is completely independent of the observations. [ABSTRACT FROM AUTHOR]

In the present paper, a 5-yr baseline integration for the period 1987–91 was carried out over a Pan-Canadian domain to validate the performance of the third-generation Canadian Regional Climate Model (CRCM). The CRCM simulated the large-scale circulation over North America well; it also correctly captured the seasonal variability of surface temperature and reproduced the winter precipitation over North America realistically. However, the CRCM systematically overestimated the summer precipitation over the continent when compared with the observed values. Extensive experiments have been conducted to trace down the sources of error of summer precipitation. Particular attention has been given to the water-vapor-related physical parameterization processes such as the mass flux convection scheme in the CRCM. Experiments involving spectral nudging of the specific humidity toward the values of large-scale driving data enabled the authors to link overestimation with abundant water vapor accumulated in the lower boundary layer resulting from an excessive amount of moisture stored in the soil. A strong boundary layer mixing process from the third generation of the Canadian Atmospheric General Circulation Model was then implemented into the CRCM along with an adjustment to the soil water holding capacity. A final analysis of a 14-month experiment showed that these modifications significantly improved the simulation of summer precipitation over North America without adversely affecting the simulation of winter precipitation. [ABSTRACT FROM AUTHOR]

The article summarizes the temperature and precipitation conditions across Canada in 2013. Topics discussed include the national temperature recorded during the season, the drier-than-normal conditions that characterized the year, and the below average national annual precipitation registered in 2013.

Describes the weather condition in Canada in December 2001. Highest temperature; Lowest average temperature; Most precipitation.

The article summarizes the temperature and precipitation conditions across North America, Central America and the Caribbean in 2013. Topics discussed include significant flooding events in Canada, the EF-5 tornado that devastated Moore, Oklahoma, and the near average annual temperatures across the Caribbean.