Qs. Chen et al., PRECIPITATION OVER GREENLAND RETRIEVED BY A DYNAMIC METHOD AND ITS RELATION TO CYCLONIC ACTIVITY, Journal of climate, 10(5), 1997, pp. 839-870
In order to calculate the vertical motion over some high mountain regi
ons, such as Greenland, an omega-equation without the quasigeostrophic
approximation in sigma-coordinates has been developed. A dynamic meth
od for retrieving precipitation over Greenland is based on this omega-
equation. The retrieved annual mean precipitation distribution for 198
7 and 1988 is in very good agreement with the observed annual accumula
tion pattern over the Greenland Ice Sheet. The major weather system pr
oducing precipitation over Greenland is the frontal cyclone. Based on
the precipitation characteristics, Greenland can be divided into five
subregions. Precipitation over the north coastal and central interior
regions primarily occurs in summer. For the three other subregions, if
the composite monthly mean sea level pressure charts for high and low
monthly precipitation amounts are constructed, a clear relationship b
etween precipitation and cyclonic activity emerges. If a mean cyclone
exists in the Labrador Sea, heavy precipitation will fall over Greenla
nd during that month. By contrast, if a mean cyclone exists near Icela
nd, precipitation over Greenland will be reduced. This is an important
relationship between Greenland precipitation and cyclonic activity. T
he cyclonic tracks near Greenland are established. A synoptic example
is used to show the relation between precipitation and a cyclone movin
g up the west side of Greenland (track B) combined with movement acros
s the southern tip of the island (track C). In this example, lee cyclo
genesis is caused by the southern part of the Greenland Ice Sheet. The
lee cyclone develops on the east coast along track C. During lee cycl
ogenesis, heavy precipitation falls over the southern region. The ''pa
rent'' cyclone moves along track B, and precipitation falls along the
west coast of Greenland. A possible feedback between cyclonic activity
and the mass balance of the Greenland Ice Sheet is proposed. On the o
ne hand, cyclonic activity has a significant influence on snow accumul
ation over the ice sheet. The development of Icelandic cyclones is not
favorable for precipitation over Greenland. On the other hand, the Gr
eenland Ice Sheet has an important dynamic effect in producing lee cyc
logenesis and affecting the frequency of Icelandic cyclones. This poss
ible feedback may be important for understanding how the mass balance
of the Greenland Ice Sheet and the Icelandic low are maintained in the
present climate state.