Abstracts
A Synoptic Weather Typing Procedure to Assess Possible Impacts of Climate Change on Freezing Rain in South Central Canada
Chad Shouquan Cheng1, Heather Auld and Guilong Li
1Environment Canada
Shouquan.Cheng@ec.gc.ca
Freezing rain is a major weather hazard that affects many parts of Canada; however, it is especially common in a corridor from Ontario to Newfoundland. In this study, principal components analysis and average linkage clustering procedure were used to automatically classify distinctive synoptic categories based on the differentiations and similarities of meteorological characteristics between and within weather types. Meteorological data for the winter months (Nov. - Apr.) of 1958/59-2000/01 were used in the analyses. The data included hourly surface observations of many weather elements and occurrence of freezing rain as well as 6 atmospheric levels of 6-hourly NCEP-NCAR upper-air reanalysis weather variables. The study area included 14 weather observing stations in Ontario, and one station in Montreal, Quebec.
Using the above procedures, 18 major synoptic types were identified for the selected 15 stations during the winter months (Nov.-Apr.) of 1958/59-2000/01. The statistical procedure was able to successfully identify 4-6 weather types most highly associated with freezing rain events in the study area. Four weather types (1-4) were most highly associated with freezing rain events at all selected 15 stations, while up to 2 additional weather types were identified at some of the stations.
Using GCM outputs and statistical downscaling methods, discriminant function analysis was used to estimate the frequencies of freezing rain-related weather types in the future climate. Climate change scenarios for two windows of time (2040-59 and 2070-89) from the Canadian GCMs (CGCM1 IPCC IS92a and CGCM2 IPCC SRES A2) and the U.S. GCM (GFDL R30 Coupled Climate Model IPCC SRES A2) were used in the analysis. Preliminary results indicated that frequencies of the freezing rain-related weather types, over north of the study area, could increase under the future climate conditions. Over south of the study area, the contrary results were shown. The results are consistent with the historical relationships between monthly total freezing rain events and monthly mean temperature.
2005-04-05 |
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