greenland climate network (gc-net) - HFT Stuttgart

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NASA Greenland Progress Report 31 4. Proposed Field Activities and Research Objectives 2005 4.1 AWS Maintenance The automatic weather station network will be maintained. In the north, the Petermann and Petermann EL stations will be serviced as part of the NSF/NASA supported field activities. Further, we will visit GITS and NASA-U along in the north-western part of the ice sheet, as well as the AWS sites NGRIP and Summit in the dry-snow region. The profile JAR2, JAR1, CU/ETH, and Crawford 1 will be serviced while at the Swiss Camp. In the southern part of the ice sheet we will service the DYE-2, Saddle, NASA SE, and Saddle (Fig. 1.1) to reactivate the satellite transmitter, download the data and collect snow stratigraphy information. 4.2 GPS Network Maintenance Our effort to monitor the ablation along a transect from the Swiss Camp to the ice margin will continue. We have installed five “smart stakes” in spring 2001 and 2002, and reduced the smart stakes network to 3 stations in 2004. We will service these remaining sites during our AWS support in the ablation region. We will continue to collect high-resolution surface topography data using Trimble Pathfinder differential GPS measurements along several transects in the lower ablation region. In addition, we will acquire a sequence Landsat TM satellite imagery during the onset of melt and melt period to monitor the spatial variation and extent of snow fields in the ablation region. 4.3 Ground Penetration Radar We have collected a number of ground penetrating radar (GPR) profiles along the western slope of the ice sheet (Jakobshavn and Kangerlussuaq region) in previous field seasons (1999, 2000, 2003). The analysis of this data set showed that the accumulation could vary up to 40% between the trough and the ridge of the undulation. The surface topography with scale length of several kilometers plays an important role for the spatial variability of accumulation, the mass transfer, and the surface energy balance. We will repeat some of these GPR measurements during the spring 2005 field season along the same profiles to verify the recent accumulation changes and high percolation events in that region. 4.4 NCEP Reanalysis, NAO, and Melt Extent We will continue the analysis of the surface temperature fields using the NCEP reanalysis and AWS data to compare the present climate with past decades. Further, we will perform a thorough statistical analysis of pressure fields and melt extent to relate to study the forcing mechanism of large-scale synoptic pattern.
NASA Greenland Progress Report 32 5. References Abdalati, W. and K. Steffen, Greenland ice sheet melt extent: 1979-1999, J. Geophys. Res., 106(D24), 33,983-33,989, 2001. Abdalati, W., and K. Steffen, Passive microwave-derived snow melt regions on the Greenland ice sheet, Geophys. Res. Lett., 22, 787-790, 1995. Ackerman, S., and K. Strabala, Discriminating clear-sky from cloud with MODIS algorithm theoretical basis document (MOD35). Madison, WI, CIMMS: 129, 1997. Bales, R.C., J.R. McConnell, E. Mosley-Thompson, and B. Csthao, Accumulation over the Greenland ice sheet from historical and recent records. J. Geophys. Res., 106(D24): 33813- 33826, 2001a. Bales, R.C., J.R. McConnell, E. Mosley-Thompson, and G. Lamorey, Accumulation map for the Greenland ice sheet: 1971-1990, Geophys. Res. Lett., 28(15): 2967-2970, 2001b. Box, J.E., Survey of Greenland instrumental temperature records: 1873-2001, Int. J. Climatol., 22, 829-1847, 2002. Box, J.E. and K. Steffen, Sublimation on the Greenland ice sheet from automated weather station observations, J. Geophys. Res., 106(D24), 33,965-33,982, 2001. Cullen, N.J., and Steffen, K., Unstable near-surface boundary layer conditions in summer on top of the Greenland ice sheet. Geophys. Res. Lett., 28, 4491-4493, 2001. Key, J. and R. Barry, Cloud cover analysis with Arctic AVHRR data 1. Cloud detection. J. Geophys Res. 94(D15), 18,521 - 18,535, 1989. Koerle, C., and P. Lemke, Alfred-Wegener-Institut für Polar- und Meeresforschung (AWI), http://awi-bremerhaven.de, 2004. Krabill, W.B., B. Thomas, C.F. Martin and R.N. Swift, Recent observations of increased thinning of the Greenland Ice Sheet measured by aircraft GPS and Laser Altimetry. International Symposium on Arctic Glaciology, Geilo/Norway, 23.-27.8.2004. Maslanik, J., and J. Stroeve. 1990, updated current year. DMSP SSM/I daily polar gridded brightness temperatures, June to September 2001. Boulder, CO: National Snow and Ice Data Center. CD-ROM. Mote T.L., and M.R. Anderson (1995), Variations in snowpack melt on the Greenland ice sheet based on passive-microwave measurements. J. Glaciol., 41, 51-60. Nghiem, S.V., K. Steffen, R. Kwok, and W.Y. Tsai, Diurnal variations of melt regions on the Greenland ice sheet, J. Glaciol., 47(159), 539-547, 2001. Ohmura, A. and N. Reeh, New precipitation and accumulation maps for Greenland. J. Glaciol. 37(125): 140-148, 1991. Rayner, N. A.; Parker, D. E.; Horton, E. B.; Folland, C. K.; Alexander, L. V.; Rowell, D. P.; Kent, E. C.; Kaplan, A. Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century J. Geophys. Res., 108 (D14), 4407 10.1029/2002JD002670, 2002.
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