Effects of el niño and la niña events on precipitation, temperature, and natural runoff volumes in Alberta, Canada

Precipitation, temperature and natural runoff volumes over the province of Alberta, Canada were associated with the two extreme phases of Southern Oscillation, namely El Nino and La Nina. Spatial and temporal data were analyzed for the 1911-1995 period for the first winter following the onset of the El Nino and La Nina cycles in Alberta. The strongest signal for El Nino and La Nina appeared in the December to February period following their onset with some signal apparent in the November to March period. This paper includes a general description of the climate processes involved and the results for the December to February period following the onset of El Niño and La Nina events. The analyses include 22 El Nino and 14 La Nina events that occurred in the study period with an update on the current 1997-98 El Nino event. The results for the December to February (winter) period following the onset of El Nino show statistically significant above-average temperatures in all areas of Alberta. Decreased winter precipitation was evident at all stations following the onset of El Nino, however differences were very small at most locations. Natural runoff volume (computed for the February to July period) on average, provided below-average values following El Nino winters.Conversely, significant below-average temperatures were found in Alberta for the winter following the onset of a La Nina event. La Nina events provided significantly above-average precipitation at all sites and subsequently, above-average natural runoff volumes were found.