Difference between revisions of "Present Day Greenland"

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'''A table of the [[Data Sources for Greenland]].'''
'''A table of the [[Data Sources for Greenland]].'''
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Revision as of 19:31, 14 April 2010


Grid Details

These are 5km resolution NetCDF files for Greenland using data from various sources interpolated, when necessary, onto the same polar stereographic projection grid.

A table of the Data Sources for Greenland.

Mapping for Greenland: Polar Stereographic(WGS84)
Standard Parallel    71.0
Latitude of Projection Origin   90.0
False Easting    0.0
False Northing    0.0
Straight Vertical Longitude from Pole   -39.0
Lower Left Corner X-Value   -800 km
Lower Left Corner Y-Value   -3400 km

Precipitation Maps

The precipitation maps below are courtesy of Bea Csatho and show the locations of data, and a comparison of the observation study and the Bromwich climate model.

Greenland: Stations Map.
Greenland: Colormaps of observational data.
Greenland: Model vs. observational data

Greenland Data Visuals

Greenland: . Greenland: .

Data Download

The recent changes to the Greenland data files can be found in the change log.

Greenland The data file contains the following fields in NetCDF format:
  • Latitude
  • Longitude
  • Ice Thickness, 5km, corrected, (Bamber 2001)
  • Bed Topography, 5km, corrected, (Bamber 2001) + bathymetry (Jakobsson et al. 2008) Data courtesy of Ed Bueler
  • Ice Surface Elevaton, 5km, corrected, (Bamber 2001)
  • Precipitation, (Burgess et al. 2009) for permanent ice, + courtesy of Bea Csatho (van der Veen, Bromwich, Csatho and Kim 2001)
  • Basal Heat Flux, Shapiro and Ritzwoller (2004) Data courtesy of Ed Bueler
  • Mean Annual Near-surface(2m) Air Temperature, (Fausto et al 2009)
  • Surface Balance Velocity - Created at the University of Montana - Jesse Johnson - July 2009
  • Interferometrically determined surface velocity (Joughin, Smith, Howat, and Scambos, in prep)
  • Time rate of change of ice sheet surface height (Bea Csathol, Toni. Schenk, C.J. an der Veen, William B Krabill, Abstract submitted to AGU 2009 Fall Meeting)
  • Land cover (Bea Csathol, Toni. Schenk, C.J. an der Veen, William B Krabill, Abstract submitted to AGU 2009 Fall Meeting)

In addition to the "standard" data set above, a parallel “developmental” data set has been created incorporating the changes described below:

Greenland develop- mental This data file (also in NetCDF format) contains the same fields described above plus some additional climate related fields. The differences between the standard data set above and this developmental data set are:
  • Bed Topography in the Jakobshavn vicinity has been revised using the "Jakobshavn Glacier Elevation Data" from the Center for Remote Sensing of Ice Sheets (CReSIS) (downloaded on 15 January 2010). Since the grid spacing of the CReSIS data is much smaller than the 5km grid used here, local spacial averages of the CReSIS data were calculated for each 5km grid point. Values on the border of the region for which there is CReSIS data were assigned an average of the new values and the original values to decrease artificial gradients outside.
  • Ice Surface Elevaton in the Jakobshavn vicinity was revised at grid points for which the new bed topography from the CReSIS data was found the be higher than the ice surface elevation. At these points the ice surface elevation was set equal to the bed elevation.
  • Ice Thickness in the Jakobshavn vicinity was revised to accommodate the CReSIS bed topography. The ice thickness at each point was calculated by subtracting the bed elevation from the ice surface elevation.

Temperature, precipitation, and related fields in the developmental data set use data produced by the Regional Atmospheric Climate Model (RACMO2/GR) at "high horizontal resolution" (~11 km) and described in Ettema J., M.R. van den Broeke, E. van Meigaard, W.J. van de Berg, J.L. Bamber, J.E. Box, and R.C. Bales (2009), "Higher surface mass balance of the Greenland ice sheet revealed by high-resolution climate modeling", Geophys. Res. Lett., 36, L12501, doi:10.1029/2009GL038110. This data was interpolated onto the standard grid using natural neighbor interpolation (based on Delaunay triangulation). The revised and new fields are listed below. Please note that the mean annual two-meter air temperature field named "presartm" in the standard data file is named "airtemp2m" in the developmental file.

  • Mean Annual Near-Surface (two meter) Air Temperature.
  • Mean Annual Surface Temperature. Janneke Ettema (personal correspondence) provides the following comment: "I would recommend to use the surface temperature as boundary condition for ice dynamic model instead of the 2 meter temperature. They might differ significantly, especially for Greenland where Ts is limited to 0C and T2m could rise over the melting point. Furthermore, T2m is a result of interpolating the temperature at the lowest atmospheric model layer and the surface temperature using a certain lapse rate. The surface temperature is a direct result from the energy balance computed at the ice sheet surface."
  • Precipitation.
  • Runoff.
  • Surface Mass Balance; the result of subtracting sublimation, evaporation and runoff from precipitation.