Evaluating the distribution of water resources in western Canada using synoptic climatology and selected teleconnections. Part 2: summer season

Abstract

Abstract: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.

Atmospheric drivers of winter above‐freezing temperatures and associated rainfall in western Canada

“…In addition, it provides new insight into winter hydroclimatic conditions, particularly as it relates to persistence of atmospheric regimes through the grouping of synoptic types into similar regimes. Previous studies evaluate trends in the frequency of synoptic types (e.g., Newton et al, ; ; Bonsal et al, ; Bonsal and Cuell, ); however, this study uses a new approach to identify statistical step‐changes in synoptic type frequency, which may be beneficial for the evaluation of thresholds related to system changes or the generation of extremes (e.g., McGregor, ). An important aspect not explored in this research is within‐type climatic trends and variability, driven by air mass thermodynamic characteristics (e.g., Kassomenos and McGregor, ; Cassano et al, ).…”

“…The organizational capabilities of SOM give rise to a visual representation of atmospheric states that facilitates analyses among synoptic types and with surface climate variables. A comprehensive description of SOM is found in Kohonen (2001) and SOM applications to synoptic circulation classification can be found in Hewitson and Crane (2002), Reusch et al (2005), Reusch (2010), Sheridan andLee (2011), andNewton et al (2014a;2014b).…”

Evaluating the distribution of water resources in western Canada using synoptic climatology and selected teleconnections. Part 1: winter season

“…The aim of this research is to identify the atmospheric drivers of winter water resource distribution in western Canada with a particular focus on changes in distribution across watershed boundaries. Note that this analysis is performed in conjunction with a companion paper evaluating summer water resource distribution (Newton et al , ). Specifically, high‐resolution spatial patterns of temperature and precipitation are identified in relation to dominant synoptic‐scale circulation patterns.…”

Climate and rivers

“…For the same region, PDO effects on flood magnitudes also exist with higher magnitude floods found to occur more frequently during a negative, as opposed to a positive PDO phase, in the upper Fraser River, Columbia River, and North Saskatchewan River Basins (Gurrapu, St‐Jacques, Sauchyn, & Hodder, ). Further north over the west Canadian Arctic, the frequency and positioning of summer and winter anticyclonic blocking and trough patterns over the Pacific Ocean and western North America, as moderated by the PDO and ENSO, are critical determinants of hydro‐climatic variations and ice melt‐dominated stream processes (Newton, Prowse, & Bonsal, , ). Across the south‐eastern United States, Clark, Nnaji, and Huang () and Risko and Martinez () have also shown ENSO and PDO influences on streamflow, whereas Sagarika, Kalra, and Ahmad () reveal strong regional effects on U.S. stream flow variability by the PDO and interdecadal variations in the Atlantic Basin.…”