Difference between revisions of "Present Day Greenland"

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==Data Download==
 
==Data Download==
  
The recent changes to the Greenland data files can be found in the [[change log]].<br>
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There are currently three different versions of the Greenland Present Day Data Set available:
 +
*Greenland Obsolescent Data Set ([[media:Greenland_5km_v0.93.nc|Greenland_5km_dev1.0.nc]])
 +
*Greenland Standard Data Set (([[media:Greenland_5km_v0.93.nc|Greenland_5km_v1.1.nc]])
 +
*Greenland Developmental Data Set ([[media:Greenland_5km_v0.93.nc|Greenland_5km_dev1.2.nc]])
 +
Each of these data sets contains the fields listed below.
  
{| border="1" cellpadding="2"
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'''Data Fields:'''
|-valign="top"
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*Longitude
|width="10%"|'''Greenland'''
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|width="70%"|The data file contains the following fields in NetCDF format:
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*Latitude  
 
*Latitude  
*Longitude
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*Bed Topography [http://nsidc.org/data/nsidc-0092.html (Bamber 2001)] and bathymetry [http://ibcao.org/ (Jakobsson et al. 2008)]Data courtesy of Ed Bueler.  See note 1 below.
*Ice Thickness, 5km, corrected, [http://nsidc.org/data/nsidc-0092.html (Bamber 2001)]
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*Ice Thickness [http://nsidc.org/data/nsidc-0092.html (Bamber 2001)].  See note 1 below.
*Bed Topography, 5km, corrected, [http://nsidc.org/data/nsidc-0092.html (Bamber 2001)] + bathymetry [http://ibcao.org/ (Jakobsson et al. 2008)] Data courtesy of Ed Bueler  
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*Surface Elevaton [http://nsidc.org/data/nsidc-0092.html (Bamber 2001)]. See note 1 below.
*Ice Surface Elevaton, 5km, corrected, [http://nsidc.org/data/nsidc-0092.html (Bamber 2001)]
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*Mean Annual Near-surface (2 meter) Air Temperature.  See note 2 below.
*Precipitation, (Burgess et al. 2009) for permanent ice, + courtesy of Bea Csatho (van der Veen, Bromwich, Csatho and Kim 2001)
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*Mean Annual Precipitation.  See note 2 below.
*Basal Heat Flux, [http://ciei.colorado.edu/~nshapiro/MODEL/ASC_VERSION/ Shapiro and Ritzwoller (2004)] Data courtesy of Ed Bueler  
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*Basal Heat Flux [http://ciei.colorado.edu/~nshapiro/MODEL/ASC_VERSION/ (Shapiro and Ritzwoller 2004)]Data courtesy of Ed Bueler.
*Mean Annual Near-surface(2m) Air Temperature, (Fausto et al 2009)
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*Interferometrically Measured Surface Velocity (Joughin, Smith, Howat, and Scambos, in preparation).
*Surface Balance Velocity - Created at the University of Montana - Jesse Johnson - July 2009
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*Surface Balance Velocity - Created at the University of Montana by Jesse Johnson in July 2009.
*Interferometrically determined surface velocity (Joughin, Smith, Howat, and Scambos, in prep)
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*Time Rate of Change of Ice Sheet Surface Height (Bea Csathol, Toni. Schenk, C.J. van der Veen, William B Krabill, Presented at the AGU 2009 Fall Meeting).
*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)
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*Land Cover (Bea Csathol, Toni. Schenk, C.J. van der Veen, William B Krabill, Presented at the 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)
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*Oxygen Isotopes Record and associated Temperature Time Series from the Greenland Ice Core Project (GRIP).
  
|width="20%"|[[media:Greenland_5km_v0.93.nc]]
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'''Notes:'''
|-valign="top"
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|}
+
  
In addition to the "standard" data set above, a parallel “developmental” data set has been created incorporating the changes described below:
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'''1.''' The bed topography in each of the three available data sets have been modified from that given by Bamber to incorporate the [http://www.cresis.ku.edu/research/data/greenland_data.html Center for Remote Sensing of Ice Sheets (CReSIS)] data in the Jakobshavn region.  In the "Obsolescent" and "Standard" Data Sets local spatial 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.  The "Developmental" Data Set uses an algorithm developed by Ute Herzfeld which preserves the continuity and depth of the trough below the glacier.  The changes to the bed topography in the Jakobshavn region also affect the ice thickness and upper surface fields.  (The upper surface is only affected at a few grid points where the Cresis data places the topography above the original upper ice surface.)
 +
 
 +
'''2.''' The climate data differs between the "Obsolescent" Data Set and the later "Standard" and "Developmental" Data Sets.  The "Obsolescent" Data Set uses the temperature parameterization of Fausto et al (2009) and a juxtaposition of precipitation data provided by Evan Burgess (Burgess et al 2009) for regions where there is permanent ice with data provided by Bea Csatho (van der Veen, Bromwich, Csatho, and Kim 2001) for regions where there is not permanent ice.  The later ("Standard" and "Developmental") Data Sets use climate data provided by Janneke Ettema [http://www.agu.org/pubs/crossref/2009/2009GL038110.shtml (Ettema et al 2009)].  This data includes Runoff, Surface Mass Balance, and Surface Temperature fields in addition to the Two-meter Temperature and Precipitaion fields.  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."
  
 
{| border="1" cellpadding="2"
 
{| border="1" cellpadding="2"
 
|-valign="top"
 
|-valign="top"
|width="10%"|'''Greenland develop- mental'''
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|width="50%"|&nbsp; Greenland Obsolescent Data Set||width="50%"|&nbsp; [[media:Greenland_5km_v0.93.nc|Greenland_5km_dev1.0.nc]]
|width="70%"|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:
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*Bed Topography in the Jakobshavn vicinity has been revised using the "Jakobshavn Glacier Elevation Data" from the [http://www.cresis.ku.edu/research/data/greenland_data.html 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.
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*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.
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*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.
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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 [http://www.agu.org/pubs/crossref/2009/2009GL038110.shtml 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.
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* Mean Annual Near-Surface (two meter) Air Temperature.
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* 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."
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* Precipitation.
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* Runoff.
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* Surface Mass Balance; the result of subtracting sublimation, evaporation and runoff from precipitation.
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|width="20%"|[[media:Greenland_5km_dev1.1.nc]]
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|-valign="top"
 
|-valign="top"
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|width="50%"|&nbsp; Greenland Standard Data Set||width="50%"|&nbsp; [[media:Greenland_5km_v0.93.nc|Greenland_5km_v1.1.nc]]
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|-valign="top"
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|width="50%"|&nbsp; Greenland Developmental Data Set &nbsp; ||width="50%"|&nbsp; [[media:Greenland_5km_v0.93.nc|Greenland_5km_dev1.2.nc]]
 
|}
 
|}
 +
 +
A description of recent changes to the Greenland data sets can be found in the [[change log]].<br>

Revision as of 18:20, 15 April 2010

Contents

Grid Details

Downloadable from this page 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

There are currently three different versions of the Greenland Present Day Data Set available:

Each of these data sets contains the fields listed below.

Data Fields:

  • Longitude
  • Latitude
  • Bed Topography (Bamber 2001) and bathymetry (Jakobsson et al. 2008). Data courtesy of Ed Bueler. See note 1 below.
  • Ice Thickness (Bamber 2001). See note 1 below.
  • Surface Elevaton (Bamber 2001). See note 1 below.
  • Mean Annual Near-surface (2 meter) Air Temperature. See note 2 below.
  • Mean Annual Precipitation. See note 2 below.
  • Basal Heat Flux (Shapiro and Ritzwoller 2004). Data courtesy of Ed Bueler.
  • Interferometrically Measured Surface Velocity (Joughin, Smith, Howat, and Scambos, in preparation).
  • Surface Balance Velocity - Created at the University of Montana by Jesse Johnson in July 2009.
  • Time Rate of Change of Ice Sheet Surface Height (Bea Csathol, Toni. Schenk, C.J. van der Veen, William B Krabill, Presented at the AGU 2009 Fall Meeting).
  • Land Cover (Bea Csathol, Toni. Schenk, C.J. van der Veen, William B Krabill, Presented at the AGU 2009 Fall Meeting).
  • Oxygen Isotopes Record and associated Temperature Time Series from the Greenland Ice Core Project (GRIP).

Notes:

1. The bed topography in each of the three available data sets have been modified from that given by Bamber to incorporate the Center for Remote Sensing of Ice Sheets (CReSIS) data in the Jakobshavn region. In the "Obsolescent" and "Standard" Data Sets local spatial 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. The "Developmental" Data Set uses an algorithm developed by Ute Herzfeld which preserves the continuity and depth of the trough below the glacier. The changes to the bed topography in the Jakobshavn region also affect the ice thickness and upper surface fields. (The upper surface is only affected at a few grid points where the Cresis data places the topography above the original upper ice surface.)

2. The climate data differs between the "Obsolescent" Data Set and the later "Standard" and "Developmental" Data Sets. The "Obsolescent" Data Set uses the temperature parameterization of Fausto et al (2009) and a juxtaposition of precipitation data provided by Evan Burgess (Burgess et al 2009) for regions where there is permanent ice with data provided by Bea Csatho (van der Veen, Bromwich, Csatho, and Kim 2001) for regions where there is not permanent ice. The later ("Standard" and "Developmental") Data Sets use climate data provided by Janneke Ettema (Ettema et al 2009). This data includes Runoff, Surface Mass Balance, and Surface Temperature fields in addition to the Two-meter Temperature and Precipitaion fields. 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."

  Greenland Obsolescent Data Set   Greenland_5km_dev1.0.nc
  Greenland Standard Data Set   Greenland_5km_v1.1.nc
  Greenland Developmental Data Set     Greenland_5km_dev1.2.nc

A description of recent changes to the Greenland data sets can be found in the change log.