TWP/SMET/C1 - Poor Performing Sensor

On 4/23/2004 condensation was found inside the target area of the ORG lens. A spare was 
sent and installed but did not solve the problem of high background voltage values causing 
rainrate values to be recorded during no rainfall.  Values range anywhere from 0.06 to 
0.12 mm/hr.  

A new Optical Rain Gage was installed on 01/19/2005 @ 13:30 GMT alleviating the high 
background voltage values that lead to consistent rainfall rates of around 0.11 to 0.15 mm/hr 
on a consistent basis.  

The formula used to calculate rainfall rates from the new Optical Rain Gage is:  RR 
(mm/hr) = 25(V^1.87) - 0.15.

Older model formula = 20(V^2) - 0.05

The two formulas result in comparable data.

• Precipitation minimum(precip_min)
• Precipitation maximum(precip_max)
• precip_sd
• Precipitation mean(precip_mean)

TWP/SMET/C1 - Upper wind sensor failure

The upper wind speed sensor was binding at low wind speeds.  Comparison to the lower wind 
sensor showed that the upper sensor flat-lines for long periods of time.  The upper 
anemometer was replaced.

• up_dir_sd
• up_spd_max
• up_spd_sd
• up_dir_vec_avg
• up_spd_vec_avg
• up_spd_arith_avg
• up_spd_min

TWP/SMET/C1 - Reprocess: Tipping bucket rain gauge added

A tipping bucket rain gauge was added to the TWP.C1 SMET suite of instruments on 20061017. 
 Effective 20060926, two new variables (count and rain amount) were added to the end of 
the twpsmet60sC1.b1 datastream.  Between 9/26 and 10/17, the data for these two variables 
are filled with zeros.  Users should not use the data during this period as the zeros 
are not representative of the rain fall at the site.  When reprocessing of this datastream 
occurs these variables will be added for the 19961009-20060926 and data from 
19961009-20061017 will be filled with -9999 (missing).

• base_time

TWP/SMET/C1 - Upper winds failure

The upper wind instrument was inoperative resulting in constant wind direction and speed.  
A failed cable was replaced.

• up_dir_sd
• up_spd_max
• up_spd_sd
• up_dir_vec_avg
• up_spd_vec_avg
• up_spd_arith_avg
• up_spd_min

TWP/SMET/C1 - Reprocess: ORG Data has very small rainrate values

The ORG data is collected via analog signal and not digital.  Therefore, we continuously 
collect data even when no rain is occurring.  We also capture small events such as leaves, 
large bugs, dust, etc blowing through the measurement path.  Because this discrete event 
occurs quickly the value is usually captured for 1 or 2 seconds.  This value is then 
averaged to the minute producing rainrate on the order of .009 mm/hr or less.  These values 
are not indicative of rain and should be removed from the record or summing over long 
periods can bias the climate record.  We are reprocessing the data to remove these small 
values and are adjusting the collection program to remove them before ingest.

• Precipitation minimum(precip_min)
• Precipitation maximum(precip_max)
• precip_sd
• Precipitation mean(precip_mean)

TWP/SMET/C1 - ORG Precip Data Incorrect

Moisture intrusion into the sensor body allowed condensation on the lens of the ORG.  
Continual and long-term precipitation was reported during this time.

• Precipitation minimum(precip_min)
• Precipitation maximum(precip_max)
• precip_sd
• Precipitation mean(precip_mean)

TWP/SMET/C1 - 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.

• lo_spd_max
• up_spd_max
• lo_spd_vec_avg
• lo_spd_min
• lo_spd_arith_avg
• up_spd_sd
• up_spd_vec_avg
• up_spd_arith_avg
• up_spd_min
• lo_spd_sd