S. Serrar et al., Mountain reference technique: Use of mountain returns to calibrate weatherradars operating at attenuating wavelengths, J GEO RES-A, 105(D2), 2000, pp. 2281-2290
The Mountain Reference Technique (MRT) was proposed as a means to perform a
self-calibration of a weather radar system operating at an attenuating wav
elength in a mountainous environment. Two convective rain events observed d
uring the Grenoble 97-98 Experiment are selected here for an illustration a
nd a further verification of the method at X band: the June 16, 1997, event
is a medium event with maximum path-integrated attenuations (PIAs) of abou
t 15 dB over a 9-km path, while the July 3, 1998, event is quite extraordin
ary with (1) a maximum PIA of 50 dB over the same distance and (2) the temp
orary presence of hail. An improved scheme is proposed for the MRT paramete
r estimation procedure with a more satisfactory treatment of such high-atte
nuation effects. It is shown that the optimal calibration factors obtained
for the two rain events are almost equal to each other, a comforting result
with respect to the radar equipment stability during the corresponding 1-y
ear period. Although the MRT is based on reflectivity and attenuation measu
rements only, validation of the rain rate retrieval algorithms with respect
to rain gage data for the June 16, 1997, rain event showed that this techn
ique is relevant in terms of rain rate estimation. In particular, the MRT-c
alibrated Hitschfeld-Bordan algorithm provides satisfactory results for thi
s medium-attenuation event. However, the July 3 case clearly demonstrates t
hat this algorithm cannot correct for such high-attenuation effects because
of its inherent instability. For both rain events the Marzoug-Amayenc algo
rithm, originally proposed for spaceborne configurations, is found to be st
able and efficient in terms of rain rate estimation. These interesting feat
ures are counterbalanced by the fact that the algorithm implementation is l
imited to directions for which PIA measurements are actually available.