Precipitation over Greenland

Direct observations of Greenland precipitation are particularly scanty. Stations with long records are limited to the coasts. As mentioned, in recent years, data over the ice sheet have been acquired from automatic weather stations. But quite a few measurements have been made of annual snow accumulation over the ice sheet. Bender ( ) provides a synthesis of observed annual accumulation (snow water equivalent) over the ice sheet, modified along the coast with a simple model of orographic precipitation. The resulting map, further modified by Bromwich et al. (1993) is provided as Figure 6.5. This is a much better analysis than can be provided from interpolating sparse station data and other coarse resolution records. The main features of the map are very low accumulation (100 mm) over the northern portions of the island with the highest values along the southeast coast. Peak values along the southeast coast exceed 2000 mm.

Figure 6.5 Annual accumulation over the Greenland Ice Sheet in mm water equivalent. The contour intervals are 200 mm, but 100 mm if smaller than 400 mm and 600 mm if larger than 1000 mm (from Chen et al., 1997, by permission of AMS).

These local features are not captured in Figure 2.25. Fairly high values are also found along the western coast related to orographic uplift and cyclone activity in Baffin Bay.

A more recent effort to assess Greenland precipitation comes from the study of Bromwich et al.(2001b). It is based on enhancements to the model of Chen etal.(1997). The dynamic model is based on the omega equation (which describes vertical motion of importance with respect to both synoptic-scale and orographic precipitation). It was driven by ECMWF data. Figure 6.6 shows the field of modeled annual precipitation for Greenland and the surrounding region averaged over the years 1985 through 1999. The modeled precipitation captures the general features seen in Figure 6.5. In particular, it reproduces the low amounts over the central ice sheet and the high values along the southeast coast. Aspects of accumulation over Greenland will be further examined in Chapter 8.

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