Data Information Page from ArcticRIMS (http://RIMS.unh.edu) Title: PRECIPITATION FROM ERA-40 RE-ANALYSIS (Serreze, Barrett) Description: This data set provides estimates of daily total precipitation from the European Center for Medium Range Weather Forecasts (ECMWF) ERA-40 Reanalysis (ECMWF 2002). Data cover the period 1 January 1979 to 31 August 2002. Data were obtained from the National Center for Atmospheric Research (NCAR) Data Support Section dataset ds117.0 (). Precipitation is archived as 6 hour accumulations of convective and large scale (Stratiform) precipitation. Daily total precipitation was computed by summing 6 hour accumulations of convective and large-scale components. Fields of total precipitation were regridded from the native N80 (roughly 1 degree resolution) reduced gaussian grid to the EASE 25km grid using a bilinear interpolation scheme. This scheme is described in ECMWF [2003]. Classification: Meteorology, Precipitation, Climate Author/PI: Vorosmarty, Charles, Richard Lammers, Mark Serreze, Andy Barrett Contact Information for original gridded daily time step data: Mark Serreze Senior Research Scientist 449 UCB, RL-2, #223 National Snow and Ice Data Center University of Colorado Boulder, CO 80309-0449 E-mail: serreze@kryos.colorado.edu Tel: 303-492-2963 Web: http://nsidc.org/research/bios/serreze.html Andy Barrett Associate Scientist 449 UCB National Snow and Ice Data Center University of Colorado Boulder, CO 80309-0449 Email: apbarret@kryos.colorado.edu Tel: 303-735-4148 Web: http://nsidc.org/research/bios/barrett.html Contact Information for all spatially and temporally aggregated data in RIMS: Charles Vorosmarty Department of Civil Engineering The City College of New York Steinman Hall, Rm T-513 140th Street & Convent Ave, NY NY 10031 USA Email: cvorosmarty@ccny.cuny.edu Tel: (212) 650-7042 Web: http://crest.ccny.cuny.edu/ Richard Lammers Water Systems Analysis Group Institute for the Study of Earth, Oceans, and Space Morse Hall, Room 211 8 College Road University of New Hampshire Durham, NH 03824-3525 USA Email: Richard.Lammers@unh.edu Tel: (603) 862-4699 Web: http://www.wsag.unh.edu/ Temporal Coverage Begin Date (year-month-day): 1979-01-01 End Date (year-month-day): 2002-08-31 Spatial Coverage: Corner coordinates in Ease Projection (Units: Meters form N.P.) (Description at http://nsidc.org/data/ease/ease_grid.html) Minimum X: -4875633.612 m Minimum Y: -4875633.612 m Maximum X: 4875633.612 m Maximum Y: 4875633.612 m Corner coordinates in Geographical projection (Units: Degrees) (Description at http://en.wikipedia.org/wiki/Equirectangular_projection) Minimum latitude: 45.0 Minimum longitude: -180.0 Maximum latitude: 90.0 Maximum longitude: 180.0 Units: mm Aggregation Method: sum General Methods: Serreze et al [2005] have evaluated monthly precipitation from ERA-40 for the north polar region (the region noth of 45N), the terrestrial Arctic drainage and the four major watersheds: the Ob, Yenisey, Lena and Mackenzie. ERA-40 precipitation was compared to an improved gridded dataset of precipitation derived from gauge data for the period 1979-1993. Precipitation from the NCEP/NCAR re-analysis, the ERA-15 re-analysis and satellite derived estimates from GPCP were also evaluated. ERA-40 precipitation is superior to NCEP/NCAR in terms of smaller biases, its ability to capture large-scale patterns of precipitation and its depiction of inter-annual variability. However, ERA-40 shows little improvement over ERA-15, especially in summer when in some cases ERA-15 out-performs ERA-40. Comments: For much of the Arctic domain, where sufficient observations are available, biases for ERA-40 precipitation are within +/- 25% by comparison with gridded gauge measured precipitation. Most of the remaining area shows negative bias, indicating an underestimation of precipitation by ERA-40. Negative biases appear to be strongest over the Arctic Ocean, Greenland and northern Europe in winter. Negative biases persist over central Greenland throughout the year but very few precipitation observations exist here. There are also some areas of large positive biases, especially where mean precipitation is low, for example the Canadian Arctic Archipelago in winter and spring. Over 50% of the cells in the north Polar region have squared correlations (shared variance) of 0.5 or greater between ERA-40 and observed precipitation. Correlations are better in January than they are in June, when convective precipitation dominates. References: European Center for Medium-Range Weather Forecasts, 2002. ERA-40 Project Report Series 3. Workshop on Re-analysis, 5-9 November 2001. European Center for Medium-Range Weather Forecasts, 443pp. European Center for Medium-Range Weather Forecasts, 2003. IFS Documentation. Part VI: Technical and Computational Procedures (CY23R4). European Center for Medium-Range Weather Forecasts, 162pp. Serreze, M. C., A. P. Barrett and F. Lo. 2005. Northern High Latitude Precipitation as Depicted by Atmospheric Reanalysis and Satellite Retrievals. Monthly Weather Review, 133(12), p3407-3430. Arctic RIMS Contact: Richard Lammers Water Systems Analysis Group Institute for the Study of Earth, Oceans, and Space Morse Hall University of New Hampshire Durham, NH 03824 Phone: (603) 862-4699 Fax: (603) 862-0587 Email: Richard.Lammers@unh.edu Web: http://wsag.unh.edu Data Archiving: This ArcticRIMS data set has been permanently stored to the ARCSS Data Archive at NCAR/EOL (http://www.eol.ucar.edu/projects/arcss) with the support of National Science Foundation grants (NSF) OPP-0230243 and Humans and Hydrology at High Latitudes (NSF) ARC-0531354