TWP/MMCR/C1 - Precipitation Mode Reflectivity Incorrect
|DataStreams:||twpmmcrspecmomC1.a0, twpmmcrC1.00, twpmmcrmomC1.b1|
The MMCR's precipitation mode is achieved by switching in one of two rf switches thereby intending to add approximately 25 dB of attenuation. This prevents the receiver and computer ADC from saturating. It now appears that the amount of attenuation actually being applied varied, and is not accurately known. The precipitation mode reflectivities values may not be quantitatively accurate. It appears that a bit more than the intended 25 dB of attenuation was applied. Mode 4 reflectivities are sometimes larger and sometimes smaller than mode 3 reflectivities. Mode reflectivity differences ranged from less than a dB, up to almost 20 dB difference. From 2008.08 on through MMCR end-of-life however, it appears that less than the 25 DBZ attenuation was being applied and that precip mode reflectivities were generally too high.
The reflectivity values should not be used in a quantitative manner.