Dynamical Downscaling of ERA-Interim Temperature and Precipitation for Alaska

The European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim) has been downscaled using a regional model covering Alaska at 20-km spatial and hourly temporal resolution for 1979–2013. Stakeholders can utilize these enhanced-resolution data to investigate climate- and weathe...

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Bibliographic Details
Published in:Journal of applied meteorology and climatology 2016-03, Vol.55 (3), p.635-654
Main Authors: Bieniek, Peter A., Bhatt, Uma S., Walsh, John E., Rupp, T. Scott, Zhang, Jing, Krieger, Jeremy R., Lader, Rick
Format: Article
Language:English
Subjects:
Bias
Climate
Climate change
Colleges & universities
Data assimilation
Elevation
Precipitation
Precipitation-temperature relationships
Remote sensing
Seasons
Simulation
Spatial distribution
Temperature
Temporal resolution
Topography
Variables
Weather
Weather forecasting
Weather stations
Wind
Winter
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Summary:The European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim) has been downscaled using a regional model covering Alaska at 20-km spatial and hourly temporal resolution for 1979–2013. Stakeholders can utilize these enhanced-resolution data to investigate climate- and weather-related phenomena in Alaska. Temperature and precipitation are analyzed and compared among ERA-Interim, WRF Model downscaling, and in situ observations. Relative to ERA-Interim, the downscaling is shown to improve the spatial representation of temperature and precipitation around Alaska’s complex terrain. Improvements include increased winter and decreased summer higher-elevation downscaled seasonal average temperatures. Precipitation is also enhanced over higher elevations in all seasons relative to the reanalysis. These spatial distributions of temperature and precipitation are consistent with the few available gridded observational datasets that account for topography. The downscaled precipitation generally exceeds observationally derived estimates in all seasons over mainland Alaska, and it is less than observations in the southeast. Temperature biases tended to be more mixed, and the downscaling reduces absolute bias at higher elevations, especially in winter. Careful selection of data for local site analysis from the downscaling can help to reduce these biases, especially those due to inconsistencies in elevation. Improved meteorological station coverage at higher elevations will be necessary to better evaluate gridded downscaled products in Alaska because biases vary and may even change sign with elevation.
ISSN:1558-8424
1558-8432
DOI:10.1175/JAMC-D-15-0153.1