GRW/WACR/M1 - Interference/False signal

Interference occurred between the WACR/SWACR beginning 9:45 GMT on 09/25.  This effect was 
not as noticeable on DQ plots until ~10 GMT on 09/27 at which time the interference was 
quite pronounced as vertical bands in the reflectivity and velocity plots.  The 
interference was slightly noticeable in the spectral width plots as well.  

Interference resulted from the SWACR using the same frequency as the WACR.  Interference 
was alleviated by changing the pulse repetition frequency (prf) from 10 kHz to 9.9 kHz.  
Some minor contamination still existed during the presence of highly reflective 
clouds/precipitation.

The Doppler velocity was not affected as much by the interference.  A cloud mask based on 
the Doppler velocity will remove most of this contamination in the reflectivity and 
spectra width measurements.

• MMCR Spectral Width(SpectralWidth)
• Reflectivity(Reflectivity)
• SignalToNoiseRatio

GRW/WACR/M1 - Coherence Filter Contamination

The coherence filter (software) that was added to the WACR under BCR-01500 was causing 
occasional contamination to WACR data.  This was exhibited in the first 2000 m of range by 
streaking in the data over a period of time. It didn't occur often and when it did, it is 
quite obvious looking at the plots.  

On 4/2/2010 at 12:00 UTC, the coherence filter was modified to preclude working on signals 
with a SNR greater than 60 dB.  The vendor thinks this will solve the problem.

• North latitude(lat)
• PowerHotLoad
• Temp_Computer_Enclosure
• Temp_Antenna_Bottom
• SignalToNoiseRatio
• heights
• PowerAmbientLoad
• Temp_LNA
• Temp_Modulator_Control
• Polarization
• PowerTransmitDriver
• Temp_Hot
• MMCR Spectral Width(SpectralWidth)
• txpower
• Temp_ambient
• Noise
• Temp_Outside
• Temp_Future
• base_time
• Altitude above mean sea level(alt)
• time
• time_offset
• wacr_status
• Temp_Chiller
• East longitude(lon)
• Reflectivity(Reflectivity)
• Temp_Antenna_Top
• Temp_Chiller_Supply
• Temp_modulator
• Temp_EIKA
• MMCR Mean Doppler Velocity(MeanDopplerVelocity)
• Temp_Chiller_Return

GRW/WACR/M1 - Reprocessed: Reflectivity and Height Offsets

The instrument vendor informed us of a range (height) offset of 13 m and provided updated 
reflectivity calibration.  All values reported for 'Reflectivity' were approximately 3 dB 
too low.   In addition, the Reflectivity in the first and fourth range gates (starting 
from the surface) needed to be further corrected by an additional 2.7 and -0.9 dB, 
respectively. The 'height' field values were 13.33 m too low.  The data were reprocessed to 
correct these problems.

The grwwacrM1.b1 data were reprocessed and archived in October 2010.  The 
grwwacrspeccmaskcopolM1.a0 and grwwacrspeccmaskxpolM1.a0 data were reprocessed and archived in January 
2012.

• Reflectivity(Reflectivity)
• heights

GRW/WACR/M1 - Transmit power drop outs

At approximately 16:27 GMT on 20090727, txpower began intermittently dropping out and 
reporting slightly negative values.  This issue continued intermittently through 20090807 
when it stopped occurring.  The problem resumed 20091006 and continued to occur on a daily 
basis until the monitor detector was replaced 20101019.

The transmit power as measured by the detector after replacement was approximately 1.3 dB 
less than when it failed.  Reflectivity measurements have a +0/-1.3 dBZ of additional 
uncertainty for this period of time.

• txpower
• Reflectivity(Reflectivity)