UBC Theses and Dissertations
An evaluation of the North American Regional Reanalysis precipitation fields in a topographically complex domain, British Columbia, Canada Hunter, Cameron
The accuracy of gridded precipitation products in mountainous environments has been shown to be unreliable compared to other geographic areas due to the complex terrain and sparse network of stations typically found in these regions. This study is an analysis of the accuracy of the North American Regional Reanalysis (NARR) precipitation dataset for the province of British Columbia. Unlike similar gridded precipitation products, the NARR has not yet been evaluated to determine how reliably it reproduces observed patterns of precipitation in this region. The objective of this study is to assess the temporal and spatial patterns of precipitation in the NARR record in order to determine how closely it reproduces observed precipitation. A comparison of the NARR precipitation records with station precipitation records was conducted to evaluate the NARR’s ability to reproduce the interannual, monthly, and daily patterns of precipitation experienced. Streamflow records and NARR precipitation records for a number of basins throughout British Columbia were examined using a water balance approach to better understand the spatial variability of errors. A structural break in the NARR data was observed in 2003, which led to larger inaccuracies in the NARR record in subsequent years. This break was caused by a decision to exclude Canadian rain gauge data from the NARR’s data assimilation process from 2003 onwards. Several clear spatial patterns were observed in the NARR precipitation data. The NARR underpredicted precipitation in mountainous regions due to inaccuracies in its digital elevation model (DEM). The NARR overpredicted precipitation in the northern region of BC’s Interior Plateau due to a lack of available rain gauge data in this area. Finally, the NARR was found to be more accurate at modelling precipitation in areas with flat terrain and adequate station coverage, such as the southern region of the Interior and the Northeast Plateau. This analysis has shown the spatial and temporal variability of errors in the NARR dataset, allowing users to recognize both the strengths and potential shortcomings of this tool.
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