GCM upper air winter synoptic links to winter precipitation in the western United States

TitleGCM upper air winter synoptic links to winter precipitation in the western United States
Publication TypeConference Proceedings
Year of Conference2002
AuthorsByme, J., Townshend I., Lapp S., and Kienzle S.
Conference Name70th Annual Western Snow Conference
Series TitleProceedings of the 70th Annual Western Snow Conference
Date PublishedMay 2002
PublisherWestern Snow Conference
Conference LocationGranby, Colorado
KeywordsCanadian Climate Center, GCM, CGCM1, Winter precipitation

Previous downscaling work based on the 1992 Canadian Climate Centre GCM (Byme et al 1999) derived future precipitation and runoff scenarios for two key locales in western North America. GCM downscaling techniqueshave proven to better replicate historical precipitation regimes for winter periods than direct GCM precipitation simulations. Here we have applied the downscaling analysis using the new runs from the CGCM1 model releasedin 2000 to develop future winter precipitation scenarios for the western United States. The downscaling methodology is described elsewhere (Lapp et al, 2001; Byme et al., 1999). The CGCM1 (3) run is a transient C02 model that accounts for the effects of greenhouse gases and the direct effect of sulphate aerosols (CCCMA, 2000). Historical synoptic frequencies and the approximate lxC02 (1962-85) upper airflow conditions are quite similar, but there are substantive variations in the approximate 2xC02 (2021-50) upper airflows. Relative occurrence (dominance) of historical synoptic patterns are statistically linked to historical winter precipitation for the study region. These linkages are used to forecast changes in future winter precipitation based on variations in synoptic pattern statistics for the 2xC02GCM upper airflow patterns. The changes in the spatial patterns of winter precipitation for the western US is presented.