Evaluation of recent precipitation studies for Greenland ice sheet

The retrieval of an accurate spatial and temporal record of contemporary Greenland precipitation is a uniquely challenging task because of the extreme variability in both atmospheric processes and the resulting precipitation distribution over relatively small spatial scales. A comparison of precipitation data sets composed of monthly mean values from recent studies shows a convergence on the general features of the long-term spatial patterns but substantial disagreement on the temporal variability both regionally and for all of Greenland. There is general agreement on a long-term Greenland average of about 35 cm yr(-1) and on long-term values for regional scales, although-differences for outlying data sets exceed 50% of the observed glaciological estimate for particular regions. A fundamental problem is the inadequate topographic representation of Greenland in the numerical analyses. Nearly all of the data sets are overly dry for high-elevation areas, as seen from comparisons with glaciological observations from Summit. The east-central region of Greenland is found to be particularly susceptible to the temporal discontinuities in data sets which employ operational analyses. In contrast, there is strong agreement among all methods on the temporal variability for the west-central region over a 15-year period. From the comparison it is concluded that none of the data sets is able to capture all of the regional-scale features. In general, however, the deficiencies of each data set are readily identifiable from comparison and evaluation in the context of circulation features. Agreement among the methods on particular regions and timescales gives increased confidence in drawing conclusions related to aspects of Greenland's precipitation climatology. In particular, an enhanced precipitation retrieval method is found to be less susceptible to data artifacts than other methods using operational analyses. In the north, anomalously high precipitation is associated with cyclonic development near the Fram Strait. For west-central Greenland the close agreement among methods is related to the dominant contribution of the mean circulation.