A synoptic‐scale climate analysis of anomalous snow water equivalent over the Northern Great Plains of the USA

Abstract

The Northern Great Plains is a region where variations in seasonal snow accumulation can have a dramatic affect on regional hydrology. In the past, one of the problems in studying snow hydrology has been obtaining information of sufficiently high temporal and spatial resolution on the water content of the snowpack. This project used a hybrid climatology of snow water equivalent (SWE) that incorporated both model and observed data. This climatology has a long time series (49 years) and a high spatial resolution (1°× 1°) sufficient for use in a climatic analysis.The long and complete time series of SWE generated in this project allowed for a comprehensive analysis of the meteorological and climate forcing mechanisms that influence the amount of SWE. The five largest (high SWE) and five smallest SWE (low SWE) accumulations on 1 March were examined. High SWE years received greater snowfall and fewer accumulated melting degree days throughout the season. Large SWE accumulations at the end of the season, however, were not always associated with deep snowpacks early in the season. Also, all five high SWE years had above normal snowfall in February. Years with small or no SWE had below-average snowfall but greater than average accumulated melting degree days.A synoptic analysis examined both atmospheric circulation and air mass frequencies to assess impacts on ablation and snowfall. A distinct difference in the frequency of different air mass during high SWE versus low SWE years was evident. High SWE years were characterized by substantially greater intrusions of the coldest and driest air mass type (dry polar). Low SWE years, in contrast, had a greater frequency of more moderate air masses (dry moderate and moist moderate). In years with above average SWE, negative departures in November-December-January-February composite 700 hPa field were evident across the continental USA and indicate a greater frequency of troughing across the study area. Low SWE years were characterized by a ridging pattern that reduced the likelihood of precipitation and may have aided in the intrusion of more moderate air masses.

Atmospheric circulation influence on the interannual variability of snow pack in the Spanish Pyrenees during the second half of the 20th century

“…The relationship between trends in the local atmospheric circulation patterns and the evolution of snow pack has been observed in other areas (Changnon et al 1993;Dettinger and Cayan 1994;Huth 2001;Grundstein 2003). Several authors also agree that changes in the local pressure fields are a response to variability of large-scale atmospheric circulation patterns (i.e.…”

“…Thus, Grundstein and Leathers (1999) and Leathers et al (2002) studied the behaviour of several components of the snow-surface energy exchanges under a range of synoptic conditions over the Northern Great Plains of the United States. Changnon et al (1993) and Grundstein (2003) proposed that the occurrence of distinct atmospheric circulation patterns determined the occurrence of wet and dry periods which affect the annual snow pack patterns across the Rockies.…”

Maximum discharge from snowmelt in a changing climate

“…Because of the complexity of these connections, the problem is usually approached at a local/regional scale by coupling distributed hydrological models – calibrated with data from a wide range of time and space scales – with suitably downscaled Global Circulation Models (GCMs) projections [ Bales et al , 2006; Barnett et al , 2005, 2008; Cayan et al , 2008; Day , 2009; Dyer and Mote , 2006; Grundstein , 2003; Huss et al , 2008; Marsh , 1999]. While this approach may be useful at short time scales (daily to seasonal), significant knowledge gaps still persist over longer (seasonal to decadal) time scales.…”

Physical Mechanisms Linking the Winter Pacific–North American Teleconnection Pattern to Spring North American Snow Depth

“…The decrease of DP air was compensated by an increase of dry moderate (DM), moist polar (MP), and moist moderate (MM) air masses that are considerably warmer than DP air, and increased temperatures in the affected areas. Grundstein (2003) followed a similar approach to study SWE variability over the U.S. northern Great Plains. High SWE years were characterized by substantially greater intrusion of the coldest and driest air masses (DP), and low SWE years have a greater frequency of more moderate air masses (DM and MM).…”