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A case study of the synoptic patterns influencing midwinter snowmelt across the northern Great Plains
Author(s) -
Grundstein Andrew J.,
Leathers Daniel J.
Publication year - 1998
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/(sici)1099-1085(199812)12:15<2293::aid-hyp797>3.0.co;2-9
Subject(s) - snowmelt , snowpack , meltwater , environmental science , climatology , snow , middle latitudes , northern hemisphere , cloud cover , atmospheric sciences , geology , meteorology , geography , cloud computing , computer science , operating system
Snow cover is found across extensive areas of the northern hemisphere during the winter and early spring seasons. Meltwater provided by this snow cover can be an important source of freshwater for agriculture, domestic uses and hydroelectric power. Rapid ablation of the snowpack, however, can also pose environmental hazards such as flooding. The ability to forecast meltwater quantities is dependent upon a knowledge of the factors influencing the snowmelt process. This paper employs a hybrid modelling and synoptic climatological approach to investigate the relationships between synoptic weather patterns, surface energy fluxes and midwinter snowmelt in the northern Great Plains. The first objective of this study is to identify distinct synoptic patterns that are associated with days where significant snow cover ablation occurred. The second objective is to evaluate the relationships between synoptic‐scale weather patterns, snow surface energy transfers and snowmelt. A case study of 21 February 1975 is used to illustrate these relationships. Unlike the other synoptic‐type studies, which rely on empirically derived energy flux data from single index sites, this study employs a physically based snowpack model to generate estimates of energy fluxes. The use of modelled fluxes instead of measured values allows for a more spatially extensive analysis as surface fluxes over the entire study region can be analysed in conjunction with the prevailing synoptic‐scale weather patterns. Three major synoptic types, characterized by the presence of a midlatitude cyclone, are associated with large midwinter snowmelt episodes in the northern Great Plains. The case study illustrates how variations in temperature, humidity, cloud cover and wind speeds associated with such cyclonic storms can play a major role in affecting snow surface–atmosphere energy exchanges. As expected, elevated wind speeds and stronger temperature and humidity gradients significantly increased the transfers of sensible and latent heat between the snow surface and the atmosphere. Increased cloud cover near the low pressure centre reduced incoming solar radiation but through counter radiation also reduced the loss of long‐wave radiation. Copyright © 1998 John Wiley & Sons, Ltd.