Metek MRR-2 - Page 37

METEK Micro Rain Radar MRR-2 Page 37
2012-03-01 Valid for MRR Service Version 6.0.0.4 / Firmware 6.00
Nnn with nn from min(h) to max(h) - Spectral Drop Densities
With the knowledge of the frequency of the Doppler-shift the calculation of the
corresponding drop fall velocity is possible (equation 1.4.3.2 in MRR Physical
Basics). Thus each FFT-line stands for a drop size interval. Chapter 2 in the
Physical Basics shows how to derive from the received spectral power the
number of drops for this drop size class, and finally  by division through the
variable class width  the spectral drop densities.
Only a sub-set of all 64 spectral bins is considered for the calculation. The
lower (min(h)) and upper limit (max(h)) depends on the height as described in
MRR Physical Basics (Fig. 7).
In case of negative values of Fnn negative drop number densities are
calculated. Although they have no physical meaning they are retained in order
to avoid statistical biases.
PIA - Path Integrated Attenuation
The two-way Path integrated attenuation by rain drops is calculated as
described in chapter 3.2 MRR-Physical Basis and is used for correction of
Nnn, Z, RR and LWC.
z - Attenuated Radar Reflectivity
1)
z is the radar reflectivity factor (see chapter 3.1 MRR-Physical Basics) without
attenuation correction
Z - Radar Reflectivity
1)
Z is the radar reflectivity factor (see chapter 3.1 MRR-Physical Basics)
RR - Rain Rate
1)
RR is the rain rate (see chapter 3.3 MRR-Physical Basics)
LWC - Liquid Water Content
1)
LWC is the liquid water content (see equation 3.2.1 MRR-Physical Basics)
1)
In case of low signal to noise ratio negative values can occur. Although they have
no physical meaning they are retained in order to avoid statistical biases.