SGP/MMCR/C1 - Poor cross polar isolation

This last spring, Sergey Matrosov pointed out that the Circular Depolarization Ratio 
measurements on the SGP radar indicated the isolation between the co and cross channels was 
only about 15 dB. Typically isolation of 25-30 dB is expected for polarization measurements 
to be useful.

We set about to see if we could identify the source of the poor isolation. Kevin Widener 
had purchased a custom built orthomode transducer and polarizer  that hadn't gone through 
any previous testing and we decided to swap it out with an ETL unit that had shown good 
isolation in the past. Kevin performed the swap a couple of weeks back and this week the 
latest archive data was available to compare results between the OMTs. 

Results from two precipitating cloud conditions, where we looked below the melting layer, 
where we expect to find domination of spherical water droplets and therefore maximum 
values for cdr  - the maximum isolation (CDR) appears to be about 17 dB. The results showed 
that the poor isolation is probably not due to the OMTs but rather to the antenna itself.

• CircularDepolarizationRatio

TWP/MMCR/C3 - Diminished Reflectivity Sensitivity

Radar sensitivity was diminished by approximately 15 - 20 dBZ during
this period.  The result is that upper level cloud tops may be missed
and thin clouds, particularly thin cirrus, may not be detected during
this period.  Reflectivity was correctly calibrated, so values are
correct where signals were detected.  The problem was caused by
lightning damage to the low noise amplifier (LNA).  The LNA was replaced
on 20060718.

• CalCheckLevel
• RxGain
• Rx290KLevel
• MinimumDetectableReflectivity
• RadarConstant
• SkyNoiseLevel
• RangeCorrectedPower
• Cloud, reflectivity, at altitude(Reflectivity)

• RxGain
• CalCheckLevel
• Rx290KLevel
• SkyNoiseLevel
• MinimumDetectableReflectivity
• CalibrationConstant
• RadarConstant

TWP/MMCR/C3 - Reprocess:   Height Error

A timing error was found in the PIRAQ MMCR's.  It resulted in recorded heights being too 
high for each radar mode by the following amounts: 
   Mode 1: 24.8756 m too high
   Mode 2: 25.6249 m too high
   Mode 3: 33.1176 m too high
   Mode 4: 33.1176 m too high
Range gate spacing was not affected.

• heights

• Heights

• C-Band Polarimetric Radar Data for Darwin, from BOM (RAW)(raw)

SGP/MMCR/C1 - Polarization Mode Problem

The cross-polarization and co-polarization modes (6 and 5) were measuring 
cross-polarization only.  This means that one of the control signals was not hooked up correctly.  The 
signals were rerouted on 4/23/2008.

The General Mode (mode 3) is a co-polarization channel and worked during this time period. 
 The reason why we don't use the general mode all of the time is that the co-pol and 
cross-pol modes are temporally closer and make a better estimation of linear depolarization 
ratio.

• Cloud, reflectivity, at altitude(Reflectivity)
• SignalToNoiseRatio
• MMCR Spectral Width(SpectralWidth)
• MMCR Mean Doppler Velocity(MeanDopplerVelocity)

• MMCR Mean Doppler Velocity(MeanDopplerVelocity)
• Cloud, reflectivity, at altitude(Reflectivity)
• MMCR Spectral Width(SpectralWidth)