TWP/MPL/C3 - False cloud detection at 15-20km

During the period specified, clouds were sometimes incorrectly detected at 15-20km.  These 
artifacts were seen as quasi-stationary layers that were clearly not atmospheric in 
origin.  A replacement instrument was installed in May 2007 to correct the problem.

• Attenuated backscatter, cross-pol(signal_return_cross_pol)
• Preliminary cloud base height above ground level, co-pol(preliminary_cbh_co_pol)
• Preliminary cloud base height above ground level, cross-pol(preliminary_cbh_cross_pol)
• Attenuated backscatter, co-pol(signal_return_co_pol)

• Attenuated backscatter(signal_return)
• Preliminary cloud base height(preliminary_cbh)

• Height of Center of Each Range Bin(Heights)

• Preliminary cloud base height above ground level, co-pol(preliminary_cbh_co_pol)
• Attenuated backscatter, co-pol(signal_return_co_pol)
• Attenuated backscatter, cross-pol(signal_return_cross_pol)
• Preliminary cloud base height above ground level, cross-pol(preliminary_cbh_cross_pol)

TWP/VCEIL/C3 - Reduced sensitivity to high clouds

The instrument had reduced sensitivity to high clouds.

The instrument produced a significant number of optical cross-talk warnings and displayed 
a reduced capacity to detect high clouds. The window was cleaned and the instrument was 
power-cycled but with no improvement. Diagnostics indicated the problem was with the 
compensation fiber cable. 

The problem was corrected by replacing this standard-window instrument (that was tilted at 
16 degrees) with a tropics unit that became available.

• Vertical visibility(vertical_visibility)
• 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)

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)