NEW ENGLAND DROUGHT AND RELATIONS WITH LARGE SCALE ATMOSPHERIC CIRCULATION PATTERNS¹

Abstract

To provide a basis for regional hydroclimatic forecasting, New England (NE) precipitation and streamflow are compared with indices for the El Niño/Southern Oscillation, the Pacific North American (PNA) pattern, and the North Atlantic Oscillation (NAO). Significant positive correlations are found between the NAO index and monthly streamflow at western inland locations, with the strongest seasonal correlations occurring in winter. Smoothed records for the winter NAO and winter streamflow are highly correlated at some sites, suggesting that interrelationships are most significant in the low frequency spectrum. However, correlations between the NAO and precipitation are not significant, so further examination of other factors is needed to explain the relationship between the NAO and streamflow. NAO related regional air temperature, sea surface temperature (SST), storm tracking, and snowfall variability are possible mechanisms for the observed teleconnection. Exceptionally cool regional air temperatures, and SSTs, and unique regional storm track patterns characterized NE's climate during the famous 1960s drought, suggesting that concurrent (persistent) negative NAO conditions may have contributed to the severity of that event. Monthly and winter averaged regional streamflow variability are also significantly correlated with the PNA index. This, along with results from previous studies, suggests that tropospheric wave character and associated North Pacific SST anomalies are also related to NE regional drought conditions.

Temporal Variability of Monthly Daily Extreme Water Levels in the St. Lawrence River at the Sorel Station from 1912 to 2010

“…Thus, this dam could account for the significant increase in extreme minimum water levels in November and December, as well as in maximum water levels in October. It should be pointed out that the 1960s decade was a dry one for the south shore of the St. Lawrence River [37,38], and the increase in water levels observed in the fall is incompatible with this drought. As for the month of October, the increase in minimum water levels after 1936 cannot be linked to any known natural or human factor, nor can the drought that took place during that decade account for this increase.…”

Impacts of Large-Scale Circulation Variability on Low Streamflows over Canada: A Review

“…A few investigations have also examined relationships between the NAO and streamflow in the northeastern United States. Significant positive correlations were found between New England river flow (since the early 20th century) and the NAO that were strongest at decadal rather than seasonal scales (e.g., Bradbury et al, 2002). It was postulated that positive winter NAO was associated with a more southerly air flow into the region causing above average temperature and precipitation and thus increased streamflow (and vice versa) (Kingston et al, 2006).…”

Variations of Twentieth-Century Temperature and Precipitation Extreme Indicators in the Northeast United States

“…These simulations were used to set conservative significance levels and thus account for any autocorrelation in each time series. For a detailed description of the methods, refer to Bradbury et al (2002).…”