Based on evaluation of recent Greenland precipitation studies, several of the deficiencies in the precipitation spatial distributions are probably related to the topographic data employed in modeling, that is here corrected by using the modern digital elevation model due to Ekholm [1996]. The topographic effect on the precipitation can be more accurately modeled by using a separation of the horizontal pressure gradient force in sigma-coordinates into its irrotational and rotational parts, which are expressed by the equivalent geopotential and geo-streamfunction, respectively. A simple large-scale condensation is also used. These procedures combined with the corrected topography of Greenland are used to enhance the original dynamic method, that is referred to as the improved dynamic method.

The two aspects of the precipitation distribution retrieved by the improved dynamic method are refined. One is the 10 cm/yr contour near Summit Greenland, and the other is a relative large precipitation area centered near the point (70^oN, 49^oW). Extensive comparisons are made between the retrieved precipitation and observed annual accumulation time series from 11 ice core sites along 2000 m contour of the ice sheet. The modeled precipitation from the original method must use scalers to have a high degree of interannual correspondence between the measured accumulation and retrieved precipitation, but the retrieved precipitation from the improved method increases at all ice core sites and a good correspondence in the interannual variations is obtained without any scaler being required. The averaged difference over all ice core sites between the year-to-year variations in modeled precipitation and observed accumulation is 11.5 cm/yr for the improved method, while that for P from ERA-15 is 14.5 cm/yr. The mean error over all ice core sites of the long-term annual value is 3.0 cm/yr for the improved method, while that for the P from ERA-15 is 4.0 cm/yr. These two errors show that the precipitation modeled by the improved method is better than the P from ERA-15. Thus, the distribution of precipitation and its interannual variations at each of the sites retrieved by the improved dynamic method are considerably improved.

The influence of the North Atlantic Oscillation (NAO) on Greenland precipitation is further explored, and it is shown that decadal variability exists in the negative correlation between precipitation amount during winter over southern Greenland and the NAO index. Large downward trends in annual precipitation amounts are present along the southeastern, southwestern, and northwestern coasts with modest increases over the interior of the ice sheet to the north of 70^oN. These modeled changes are inferred to be responsible for most of the ice surface elevation changes measured by airborne laser-altimetry in the 1990s [Kraybill et al., 2000], particularly the large coastal thinning.