Canadian Precipitation Patterns Associated with the Southern Oscillation (original) (raw)
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Trends in Canadian precipitation intensity
Atmosphere-Ocean, 2000
Past research has unveiled important variations in total precipitation, often related to large-scale shifts in atmospheric circulation, and consistent with projected responses to enhanced greenhouse warming. More recently, however, it has been realized that important and influential changes in the variability of daily precipitation events have also occurred in the past, often unrelated to changes in total accumulation. This study aims to uncover variations in daily precipitation intensity over Canada and to compare the observed variations with those in total accumulation and two dominant modes of atmospheric variability, namely the North Atlantic Oscillation (NAO) and the Pacific/North America teleconnection pattern (PNA). Results are examined on both annual and seasonal bases, and with regions defined by similarities in monthly variability.
International Journal of Climatology, 1999
Teleconnections among El Niño and La Niña events, North Pacific sea surface temperature anomalies, and summer (June, July, August) extended dry spells on the Canadian Prairies are documented and analysed. For the period 1948-1991, results show the majority of El Niño events associated with a persistent North Pacific SST anomaly pattern consisting of anomalously cold water in the east-central North Pacific and anomalously warm water along the west coast of North America. The average number of summer extended dry spells on the Prairies associated with El Niño events is significantly higher than for non-El Niño periods. This relationship occurs during the second summer following the mature stage of El Niño events. Further analysis reveals that La Niña events are associated with opposite North Pacific SST anomaly patterns that also tend to persist for several seasons. The average number of summer extended dry spells associated with these events is significantly lower than for non-La Niña periods. Even though the relationships among El Niño, La Niña, North Pacific SST anomalies, and extended dry spells show high variability, the results of this study may be considered as an initial step towards contributing to a long-range forecasting technique of summer extended dry spells on the Canadian Prairies.
Journal of Hydrometeorology, 2019
In the past few decades, there have been more extreme climate events occurring worldwide, including Canada, which has also suffered from many extreme precipitation events. In this paper, trend analysis, probability distribution functions, principal component analysis, and wavelet analysis were used to investigate the spatial and temporal patterns of extreme precipitation events of Canada. Ten extreme precipitation indices were calculated using long-term daily precipitation data (1950-2012) from 164 Canadian gauging stations. Several large-scale climate patterns such as El Niño-Southern Oscillation (ENSO), Pacific decadal oscillation (PDO), Pacific-North American (PNA), and North Atlantic Oscillation (NAO) were selected to analyze the relationships between extreme precipitation and climate indices. Convective available potential energy (CAPE), specific humidity, and surface temperature were employed to investigate potential causes of trends in extreme precipitation. The results reveal statistically significant positive trends for most extreme precipitation indices, which means that extreme precipitation of Canada has generally become more severe since the mid-twentieth century. The majority of indices display more increasing trends along the southern border of Canada while decreasing trends dominated the central Canadian Prairies. In addition, strong teleconnections are found between extreme precipitation and climate indices, but the effects of climate patterns differ from region to region. Furthermore, complex interactions of climate patterns with synoptic atmospheric circulations can also affect precipitation variability, and changes to the summer and winter extreme precipitation could be explained more by the thermodynamic impact and the combined thermo-dynamic and dynamic effects, respectively. The seasonal CAPE, specific humidity, and temperature are correlated to Canadian extreme precipitation, but the correlations are season dependent, which could be positive or negative.
The impact of El Nino southern oscillation on central Canadian floods and droughts
Canadian Journal of Civil Engineering, 1995
A comparison of flood and low flow magnitudes during periods of El Nino and outside those periods led to the conclusion that flood risk in central Canada is not constant from year to year. This finding has implications for water resources management, particularly flood forecasting and reservoir operation.
The Ohio Journal of Science, 2021
Continental-scale studies of North America suggest that the El Niño Southern Oscillation (ENSO) can cause winters to be warmer, with less precipitation, during El Niño conditions and colder, with more precipitation, during La Niña conditions in the Midwest United States. Two sources of historical records of precipitation and temperature in southwest Ohio from 1896 to 2016 were analyzed. Three statistical methodologies were used to test the hypothesis that anomalies in winter temperature and precipitation occurred in relation to ENSO phases. Eighty percent of El Niño winters had below-average winter precipitation; the average anomaly was −5 cm. Precipitation decreased with increase in El Niño strength as measured by the Multivariate ENSO Index (MEI). These results were statistically significant beyond the 95% level. However, variation in MEI only accounted for 3% of the overall variability in winter precipitation. Many of the drier winters on record, including the extrema, occurred d...
Atmospheric and oceanic variability related to dry regimes in Canada
This study documents and assesses the atmospheric and oceanic variability associated with growing season (May to August) droughts over the Canadian Prairies. For comparison, extreme wet seasons or pluvials are also examined. Using the Palmer Z-Index as a drought indicator, extreme dry and wet seasons are firstly identified for the period 1950 to 2007. Inter-relationships among several atmospheric parameters including large to synoptic-scale circulation patterns, low-level moisture transport, moisture convergence, precipitable water content, and cyclone frequency are then assessed during extreme drought and pluvial periods. In addition, links to the previous winter's global sea-surface temperature (SST) patterns are identified using the multivariate technique of singular value decomposition. These circulation patterns over western North America and their associated moisture transport anomalies into the Prairies show some linkages to previous winter SST patterns both globally, and...
Classification of El Niño and La Niña years for water resources management in Alberta
Canadian Journal of Civil Engineering, 2018
Classification of El Niño and La Niña years in a historical time period is necessary to analyze their impacts on hydrology and water resources management. In this study, various El Niño-Southern Oscillation (ENSO) indices, and how they are used to classify El Niño or La Niña years have been reviewed. Based on the review, a simple method of classifying El Niño or La Niña years has been proposed.
Journal of Climate, 1997
In past research the Southern Oscillation index has often been used as an indicator of the tropical Pacific climate, notably for El Niño and La Niña event occurrences. This study identifies calendar monthly teleconnection signals in central and eastern North American precipitation associated with an alternative tropical Pacific indicator, sea surface temperature anomaly (SSTA) patterns. Using an approximate 1Њ resolution set of monthly precipitation totals for 1950-92, the work identifies monthly teleconnection relationships and their intraseasonal evolution. This builds upon previous studies that were limited to seasonal timescales. Here, a unique two-way statistical analysis is used to delineate linear SSTA-precipitation teleconnection patterns. First, a principal component analysis (PCA) is performed on a monthly tropical Pacific SSTA dataset for 1950-92 to identify the coherent modes of variability. The principal component (PC) score time series representing the most significant modes of SSTA variability (see below) are then correlated on a calendar-monthly basis with station precipitation anomalies, yielding associated ''correlation-based'' precipitation coherencies. In the second approach, PCA is applied to the precipitation anomaly data for each calendar month. Then, the resulting ''PC-based'' precipitation coherencies most central to each of the major correlation-based precipitation regions are identified, and their associated PC score time series are subsequently correlated with the tropical Pacific SSTA grid-cell data, yielding correlation-based SSTA coherencies that are then compared (generally favorably) with their PC-based forerunners. The three SSTA PC patterns used to seek teleconnection signals in central and eastern North American precipitation are the first unrotated PC (UPC1, emphasizing central tropical Pacific variability), and the first (VPC1, eastern tropical Pacific) and second (VPC2, western to north central tropical Pacific) Varimax-rotated PCs. The strongest such signals to emerge were for precipitation in the southeastern United States (positive association with UPC1 and VPC1 in November-March), Texas (positive association with UPC1 and VPC1 in November-March), the Great Lakes/Ohio River region (negative association with UPC1 and VPC1 in January-March), the southeastern United States (negative association with UPC1 and VPC1 in July-August), the southern Canadian prairie (negative association with UPC1 and VPC1 in November-January), and along a northern storm track (positive association with VPC2 in September-October). These results, derived from new datasets using a unique statistical approach, both broadly confirm and significantly clarify previous findings and present striking new associations. * Based on a B.S. (Honors) thesis that was awarded first prize in the 1994 Father James B. Macelwane Awards in Meteorology, sponsored by the American Meteorological Society.
Recent variations in seasonality of temperature and precipitation in Canada, 1976-95
International Journal of Climatology, 2002
A previously reported analysis of rehabilitated monthly temperature and precipitation time series for several hundred stations across Canada showed generally spatially coherent patterns of variation between two decades (1976-85 and 1986-95). The present work expands that analysis to finer time scales and a greater number of stations. We demonstrate how the finer temporal resolution, at 5 day or 11 day intervals, increases the separation between clusters of recent variations in seasonal patterns of temperature and precipitation. We also expand the analysis by increasing the number of stations from only rehabilitated monthly data sets to rehabilitated daily sets, then to approximately 1500 daily observation stations. This increases the spatial density of data and allows a finer spatial resolution of patterns between the two decades. We also examine the success of clustering partial records, i.e. sites where the data record is incomplete. The intent of this study was to be consistent with previous work and explore how greater temporal and spatial detail in the climate data affects the resolution of patterns of recent climate variations. The variations we report for temperature and precipitation are taking place at different temporal and spatial scales. Further, the spatial patterns are much broader than local climate regions and ecozones, indicating that the differences observed may be the result of variations in atmospheric circulation.