Geoscience Reference
In-Depth Information
Fig. 2. Radar measurements in a snowstorm in Finland 2 Feb 2010. RHI north of radar to range
of 150 km, horizontal lines at every 2 km (upper panel) and PPI with elevation of 1.5 degrees,
rings at each 100 km (lower panel). Reflectivity values are between -15 and +25 dBZ.
3. Fallspeeds of solid hydrometeors
Terminal fallspeeds of hydrometeors are influenced by their type and size, and hence
Doppler spectra measured with vertically pointing radar can be used for hydrometeor
classification. Barthazy and Schefold (2006) showed that the fall velocity of snowflakes
consisting of needles or plates is strongly dependent on the riming degree. The average fall
velocity of any type of snowflakes of diameter of 1 mm or larger is typically between 1 and 2
m s
−1
. In cases when hydrometeor types change, or two types of hydrometeors coexist in
same measurement volume, Doppler spectra can provide valuable information of cloud
physical processes such as riming and aggregation. In addition of academical interest they
may provide value in aviation weather services.
