NIM/ECOR/M1 - Flux Data Suspect for Some Wind Directions

NIM: For some wind directions the horizontal fetch was not representative of the field in 
which the AMF was located.  Therefore, for the wind direction ranges 90-170 (buildings) 
and 220-280 (trees) degrees, the fluxes are affected by insufficient fetch and  surfaces, 
buildings, or vegetation that are not similar to the local field conditions.

• Corrected sensible heat flux(h)
• Latent heat flux(lv_e)
• CO2 flux(fc)
• friction velocity(ustar)

NIM/ECOR/M1 - Effects on ECOR CO2 Flux and Concentration By Aircraft

Aircraft landings, departures, and running aircraft on the airport pad
were found to produce large spikes in the half hourly CO2 flux and small spikes in CO2 
concentration on many days during the entire deployment of the AMF at NIM.  This influence 
was found on 40% of the days in March and April 2006 and sometimes for multiple periods in 
a day; this was typical of  the year of data.  The spikes range from only several 
micromoles s-1 m-2 to one hundred or more for flux (a typical spike was in the twenties) and 
near zero to 1.0 mmoles m-3 for CO2 concentration (typically around 0.15).

The aircraft influence was caused by persistent easterly winds; the airport
terminal pad and the nearest part of the runway were almost directly to the
east of the ECOR location.

Occasionally an influence on water vapor density was detected, but this was fairly rare 
and usually of very small magnitude.

• covariance wc(cvar_wc)
• covariance uc(cvar_uc)
• rotated covariance wc(cvar_rot_wc)
• covaraince vc(cvar_vc)
• CO2 flux(fc)
• rotated covariance vc(cvar_rot_vc)
• covariance tc(cvar_tc)
• Mean CO2 density(mean_c)
• rotated covariance uc(cvar_rot_uc)
• variance of variable c(var_c)

NIM/MET/M1 - ORG underestimated precipitation

The ORG underestimated precipitation by about 38% during the entire NIM deployment.  No 
troubleshooting technique or replacement of gauge was successful in correcting the problem.

• ORG precipitation rate mean(org_precip_rate_mean)

NIM/MET/M1/S1 - 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.

• Rain, surface, 1-min avg(precip_rate_mean)
• precip_rate_sd
• precip_rate_max
• precip_rate_min

NIM/MET/M1 - 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.

• Wind speed vector mean(wspd_vec_mean)
• Wind speed, lower, 1-min avg(wspd_arith_mean)

NIM/MET/S1 - 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.

• wind_spd_arith_min
• Vector-averaged Wind Speed(wind_spd_vec_avg)
• Wind speed, lower, 1-min avg(wind_spd_arith_avg)
• wind_spd_arith_max
• wind_spd_arith_sd

NIM/MET/M1 - PWD cumulative precipitation incorrect

The Present Weather Detector is a serial sensor.  The MET system datalogger reads in the 
data from this sensor.  During the time in question serial comms problems were causing the 
data from the sensor to be read incorrectly.  The data for one variable showed up in 
data for another variable or not at all.  We reprocessed the data to correct as much of this 
error as we could.  The cumulative rainfall variable was calculated from the 
instantaneous rainfall variable during reprocessing.  Since we cannot be entirely sure all 
cumulative rainfall values are correct or were completely captured the cumulative rainfall data is 
considered to be unreliable.  This issue shows up when comparing the cumulative rainfall 
data at the end of the day 07/31/2006 (79.08) and the beginning of the next day 
08/01/2006 (3.17).  Clearly we were either under or over-estimating the cumulative rainfall.

• pwd_cumul_rain

NIM/MET/M1 - PWD 1 minute rainfall data suspect

The Present Weather Detector is a serial sensor.  The MET system datalogger reads in the 
data from this sensor.  During the time in question serial comms problems were causing the 
data from the sensor to be read incorrectly.  The data for one variable showed up in 
data for another variable or not at all.  We reprocessed the data to correct as much of this 
error as we could. We cannot be entirely certain that all rainfall values are correct or 
were captured properly.  It is possible that some values were missed completely.

• pwd_precip_rate_mean_1min