Comparison and Validation of Arctic Precipitation Fields from Three Atmospheric Reanalyses: CFSR, MERRA, ERA-Interim

• Main Author: Hurley, Allison R.
• Format: Text
• Language: unknown
• Published: CU Scholar 2014
• Subjects: Arctic; Atmospheric Reanalysis; CFSR; ERA-Interim; MERRA; Precipitation; Geography; Physical and Environmental Geography; Merra; North Atlantic
• Online Access: https://scholar.colorado.edu/geog_gradetds/75; https://scholar.colorado.edu/cgi/viewcontent.cgi?article=1077&context=geog_gradetds

The intent of thesis project was to investigate Arctic precipitation from three atmospheric reanalyses: Modern Era Retrospective Analysis for Research and Applications (MERRA), Climate Forecast System Reanalysis (CFSR), European Centre for Medium-Range Weather Forecasts Reanalysis-Interim (ERA-Interim). The first objective of the study was to determine if the three atmospheric reanalyses provide an accurate depiction of seasonal precipitation patterns. Spatial variability, recent trends, and anomalies in Arctic precipitation were investigated. The second objective was to conduct a statistical validation of each of the reanalysis products through a comparison with monthly GHCN station observations. Monthly precipitation fields were investigated for the period spanning January 1979 - December 2010. Overall, MERRA, CFSR, and ERA-Interim captured the known average monthly precipitation patterns across the Arctic. One notable discrepancy with ERA-Interim's precipitation field exists across the northern North Atlantic and is further investigated using nearby coastal station data. Station observations were then used to validate the reanalyses across the entire Arctic. Bias, correlations, root mean-squared error were calculated. The largest inconsistency between the reanalyses and the station observations exists in summer; smaller biases and errors exist in winter. However, associated model errors and biases are found to be related to the number of observations utilized. The ability to pinpoint the best reanalysis for use in Arctic hydrologic studies lies in further investigation of the precipitation assimilation process in each reanalysis as well as an improvement in the accuracy of gauge measurements.