USAP-DC Dataset# 601056
2017-09-13
http://doi.org/10.15784/601056

abstract:
We produce a reconstruction of surface mass balance (SMB) (in mm w.e. per year) by adjusting the 1979-2014 RACMO2 SMB to the spatial pattern of ground-penetrating radar observations and to observations of SMB from sonic height rangers.

Instruments and devices:
Ground penetrating radar systems were used to map spatial patterns in SMB, while sonic height sensors, operated on in situ automatic weather stations, provided SMB magnitude. Please see manuscript for further details.

Acquisition procedures:
Please see manuscript for specific details.

Content and processing steps:
NetCDF file including SMB (in mm w.e. per year), SMB error, and normalized SMB, along with latitude and longitude for each grid point. 

The 1979-2014 average SMB from RACMO2 was normalized with respect to its spatial mean, and so were the GPR data. Next, we determined a linear regression of the normalized RACMO2 SMB values to the normalized GPR data. We used this regression to adjust the RACMO2 SMB to maximize its match to the GPR data while conserving the spatial mean SMB. The result, shown in Figure 10c (Kuipers Munneke et al. (2017), is a RACMO2-guided extrapolation of the GPR over the unsurveyed portions of LCIS, in which the spatial pattern of RACMO2 SMB is adjusted to the spatial pattern of the GPR observations. The next step was to adjust the absolute values of RACMO2 SMB to available sonic height ranger observations. We converted RACMO2 SMB back from normalized to absolute values, again using the spatial mean SMB. We determined a weighted mean bias between RACMO2 SMB and all available sonic height ranger observations, selecting the periods for which both were available. We used the length of the height ranger observation period as a weight for the averaging, reflecting that short-term variability plays a smaller role in longer time series. Compared to the sonic height rangers, RACMO2 underestimated SMB by 14%. Applying a bias adjustment leads to the gridded SMB shown in Figure 10a. An estimate of SMB uncertainty wasbased on (1) the fit between normalized GPR and RACMO2 SMB, and on (2) the 10% uncertainty of the RACMO2 bias. The resulting uncertainty is typically 15% of the SMB value, shown in Figure 10b.

Limitations and issues:


Checkboxes:
* All the data are referenced in time and space.
* The data column, properties, and attributes listed/used in the data files are explained either in the description and/or the data files themselves.
* Graphs and maps (if provided) have legends.