TWP/VCEIL/C3 - low receiver sensitivity

The ceilometer reported frequent receiver alarms. There are periods when the receiver 
sensitivity dropped to about 50%. The problem was corrected by replacing the instrument with 
a spare.

• Lowest cloud base height detected.(first_cbh)
• Vertical visibility(vertical_visibility)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Backscatter sum(sum_backscatter)
• Second lowest cloud base height(second_cbh)
• Third cloud base height(third_cbh)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Altitude of highest signal(alt_highest_signal)
• Millivolts at internal ADC input (0 to 2500)(background_light)

TWP/SMET/C3 - ORG data noisy due to degraded ground

SMET Rain Data began to be noisy during December 2005 and the problem slowly became worse 
over time so that in February 2006 the ORG was reporting with a constant background value 
of around 0.10 mm/hr rain rate.  ORG voltage showed a near constant value above the 85mV 
threshold.  The ground for the ORG had become degraded and was lost due to corrosion.

• Precipitation mean(precip_mean)
• Precipitation maximum(precip_max)
• Precipitation standard deviation(precip_sd)
• precipitation minimum(precip_min)

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.

• First Order Estimate of Spectral Count Calibration(CalibrationConstant)
• Radar Constant(RadarConstant)
• Receiver Gain(RxGain)
• Receiver Sky Noise(SkyNoiseLevel)
• Minimum detectable reflectivity(MinimumDetectableReflectivity)
• Receiver 290K Level(Rx290KLevel)
• Receiver Cal Check Level(CalCheckLevel)

• Receiver Sky Noise(SkyNoiseLevel)
• Receiver Cal Check Level(CalCheckLevel)
• Minimum detectable reflectivity(MinimumDetectableReflectivity)
• Range Corrected Calibrated Power(RangeCorrectedPower)
• Receiver 290K Level(Rx290KLevel)
• MMCR Reflectivity(Reflectivity)
• Radar Constant(RadarConstant)
• Receiver Gain(RxGain)

TWP/SMET/C3 - Reprocess: Tipping bucket rain gauge added

A tipping bucket rain gauge was added to the SMET suite of instruments effective 20060926. 
 Two new variables (count and rain amount) were added at the end of the twpsmet60sC1.b1 
datastream.  When reprocessing of this datastream occurs these variables will be added 
with -9999 (missing) as the value for dates prior to gauge installation.

• base time(base_time)

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.

• Height of Center of Each Range Bin(Heights)

• Raw data stream - documentation not supported(raw)

• Array of heights for each power(heights)

TWP/SMET/C3 - Wind Speed data contain offset due to induced voltage

The marine model of the RM Young wind sensor needs twisted pair shielded cable.  The 
manufacturer did not originally supply the pigtail with twisted pair shielded cable.  Use of 
twisted pair shielded cable for the rest of the cable run to the logger was also not 
specified.  This caused an induced voltage in the wind speed line from the wind direction 
excitation.  The induced voltage varied from sensor to sensor and probably changed anytime 
the cable was replaced or parts of the wind sensor were repaired or replaced. The induced 
voltage has been seen to vary from 0.15 m/s to as much as 1.08 m/s.

• Upper sensor, wind speed maximum(up_spd_max)
• Lower sensor, wind speed minimum(lo_spd_min)
• Lower sensor, wind speed standard deviation(lo_spd_sd)
• Lower sensor, wind speed maximum(lo_spd_max)
• Upper sensor, wind speed arithmetic average(up_spd_arith_avg)
• Lower sensor, wind speed vector average(lo_spd_vec_avg)
• Upper sensor, wind speed minimum(up_spd_min)
• Lower sensor, wind speed arithmetic average(lo_spd_arith_avg)
• Upper sensor, wind speed vector average(up_spd_vec_avg)
• Upper sensor, wind speed standard deviation(up_spd_sd)