Evaluation of reanalysis precipitation estimates in the Canadian precipitation analysis (CaPA)
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Date
2016
Authors
Choi, Hyaesun
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Abstract
Canadian Precipitation Analysis (CaPA) has been developed by Environment Canada
to produce the most accurate near-real-time gridded precipitation estimates. It uses
the Global Environmental Multiscale model (GEM) as a background and assimilates
the synoptic network of weather stations through Optimal Interpolation. Accurate
estimation of gridded precipitation is useful for hydrological modeling, stream ow
forecasting, and climate change studies. However, the calibration and validation of
hydrologic models requires long temporal coverage of data for a better performance.
Since GEM/CaPA data are available only for the recent past (2002-present), the development
of historical data sets starting earlier than 2002 becomes important. Using
alternative models for producing the atmospheric gridded background is one solution
to overcome the short temporal coverage of archived GEM data. This thesis evaluates
and analyzes two candidate data sets. ERA-Interim and NARR were selected
as potential alternatives to GEM background. The general conclusion of the study is
that the use of ERA-Interim and NARR as background elds leads to performance
results that are not signi cantly inferior to GEM after assimilation with stations in
the CaPA framework. While result with the GEM background remains the best, one
can cautiously conclude that for most practical applications, ERA-Interim and/or
NARR may be used for the period that predates archived GEM data. The thesis
presents a more detailed evaluation of ERA-Interim and NARR for di erent seasons
and di erent regions of Canada.
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Keywords
CaPA, Reanalysis data, Precipitation