Vertical Profiles Over Flat Terrain - Wind Energy Meteorology: Atmospheric Physics for Wind Power Generation - page 55

Fig. 3.15 Suitable synoptic conditions for the formation of nocturnal low-level jets are in the
shaded area
Fig. 3.16 Frequency of the occurrence of nocturnal low-level jets over Northern Germany as
function of Central European circulation type (Grosswetterlage, Gerstengarbe et al. 1999 ) from
two years of SODAR data at Hannover (Germany) from autumn 2001 to summer 2003
Fig. 3.16 by the occurrence frequency of the respective weather types during the
same observation period. There are two weather types where the occurrence fre-
quency is identical to the occurrence frequency of the low-level jets during this
weather type. This means that in every night when this weather type prevailed a
low-level jet was observed. This is indicated by a low-level jet efficiency of 1.0 in
Fig. 3.17 . Small deviations from unity are due to the limited sample size evaluated
for this purpose. These two weather types are ''HNFA'' and ''HFZ'' which are both
related to high-pressure systems to the North of the investigation site.