M ET E K
M ic r o R a i n R a d a r M R R - 2
26
10.2010 Valid for MRR Service Version ≥ 5.2.0.9
Sampling Frequency
Number of samples per second of the analogue input signal of the MRR-2.
This parameter can‟t be changed by the user.
Calibration Constant
This constant is needed for converting the engineering units of the receiver
signal (raw data) into physical units (instantaneous and averaged data). See
Physical Basis for details. The calibration constant is factory set. Nevertheless
it can be changed by the experienced user. Before a new calibration constant
can be entered the “changing” button must be pressed. It should be only done,
if there is clear evidence for a miss-calibration of the MRR. This can be in-
ferred for example from rain rates measured with the MRR (
MRR
R
) and a rain
gauge (
RG
R
) respectively. If
old
C
is the old calibration constant, the new cali-
bration constant
new
C
can be calculated according
MRR
RG
old
new
R
R
C
C
It should be kept in mind that comparisons of rain rates measured aloft with
the MRR and a rain gauge are not straightforward due to the strong inhomo-
geneity of rain. MRR data should be taken from range gates not below the 3
rd
range gate, because approximations in the radar equation cause larger biases
at lower range gates. On the other hand the measuring height should not ex-
ceed 200 m in order to keep attenuation effects small (they are only eliminated
in case of correct calibration) and to keep the correlation with surface precipi-
tation at a useful level. Further make sure that the MRR rain retrieval is not
affected by the ice phase or melting processes. Strong winds should also be
avoided since rain gauges tend to unreliable under such conditions.
OK
All changes in the Device Parameters Menu become effective by clicking the
“OK” button. Then the corresponding commands are transmitted to the RCPD
firmware. Clicking the “Cancel” button cancels all changes.
