Data Information Page from ArcticRIMS (http://RIMS.unh.edu) Title: 2m AIR TEMPERATURE FROM ERA-40 RE-ANALYSIS (Serreze, Barrett) Description: This data set provides estimates of daily mean two meter air temperature 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 (). Two meter temperatures are archived as 6 hour mean values. Daily means were computed from these values. Data 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]. The ERA-40 system assimilates available surface temperature observations. Fields should therefore be superior to those from the NCEP/NCAR re-analysis, in which there is no assimilation of surface temperature data. Classification: Meteorology, 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: Degrees K Aggregation Method: average General Methods: ERA-40 temperatures have been evaluated for the Arctic region (north of 60º N). ERA-40 temperatures were compared with surface air temperature from the International Arctic Buoy Program/Polar Exchange at the Sea Surface (IABP/POLES) data set [Rigor and others 2000]. Monthly bias fields for ERA-40 temperatures were computed with respect to monthly mean surface air temperatures computed from the IABP/POLES data set. Grid cells in the IABP/POLES data set with less than 30 observations were not included in the analysis. This excludes much of the land area between November and April. ERA-40 surface air temperature compares well with the IABP/POLES data set where sufficient data are available for comparison. In general, biases for the central Arctic Ocean are between -3º C and 3º C in all months. In spring, ERA-40 temperatures are slightly higher than IABP/POLES around the North Pole. Cold biases appear off the N. Greenland coast and in the East Siberian Sea between November and January. Land regions appear to have cold bias between April and October. A persistent warm bias is present in the North Atlantic and Barents, Greenland and Norwegian Seas for much of the year. Central Greenland has a persistent cold bias throughout the year. These two regions are data-poor regions in the IABP/POLES data set [Rigor and others 2000]. Comments: Gridded values of temperature in the ERA-40 and IABP/POLES data sets were correlated for the period 1979 to 1997. Air temperatures for April through September for land areas are well correlated (greater than 0.6). Strong correlations exist for the Arctic ocean in April and May. However, temperatures are not so well correlated for ocean regions and Greenland between June and August. 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. Rigor, I. G., R. L. Colony and S. Martin. 200. Variations in Surface Air temperature Observations in the Arctic, 1979-97. Journal of Climate, 13, p896-914. 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