TWP/MWR/C2 - Uncertainty in clock time

At ARCS2, the MWR computer clock was not being updated because no NTP time service 
software was installed on the computer. During Nauru99, on 6/24/99, the clock was found to be 3 
minutes and 17 seconds fast. 

Assuming that the time was properly set at installation on 10/26/98 (which is not 
indicated in the installation report) and never reset until 6/24/99, the rate of time drift on 
the computer was about +0.8 seconds per day. However, if the time was not reset since 
integration at AIS on 1/14/98 (which is recorded in my integration notes), then the rate of 
drift is about +0.4 seconds per day.

The computer was replaced and time service started on 7/30/99.

• tipsky23
• tkair
• base_time
• tnd_nom31
• tkxc
• actaz
• wet_window
• r23
• tnd23I
• tc23
• time_offset
• tnd_nom23
• tnd23
• r31
• bb23
• bbn31
• tkbb
• bbn23
• tnd31
• tc31
• tknd
• bb31
• actel
• tnd31I
• tipsky31

• tnd23
• sky23
• Total liquid water along LOS path(liq)
• bbn23
• tkbb
• tc23
• tkxc
• tnd31
• bbn31
• base_time
• tnd_nom23
• Temperature, Sky Infra-Red(sky_ir_temp)
• time_offset
• bb31
• Temperature, brightness, longwave(ir_temp)
• actel
• wet_window
• 23.8 GHz sky brightness temperature(tbsky23)
• sky31
• 31.4 GHz sky brightness temperature(tbsky31)
• tnd_nom31
• tkair
• tknd
• Total water vapor along LOS path(vap)
• bb23
• tc31
• actaz

TWP/C2/SMET Wind Speeds

Beginning on December 24, Anemometer #1 (there are two anemometers on
the SMET stand) occasionally reported wind speed values that were low
relative to the other sensor.  It is clear from the data that the low
reading here is the anomalous one.

• Wind #1 speed minimum(wind1_spd_min)
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• wind1_dir_sd
• wind1_spd_sd
• Wind #1 speed maximum(wind1_spd_max)
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Wind #1 speed maximum gust(wind1_spd_max_gust)
• Wind #1 direction vector average(wind1_dir_vec_avg)

• Raw data stream - documentation not supported

• wind1_spd_sd
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• wind1_dir_sd
• Wind #1 speed maximum(wind1_spd_max)
• Wind #1 speed minimum(wind1_spd_min)
• Wind #1 direction vector average(wind1_dir_vec_avg)
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Wind #1 speed maximum gust(wind1_spd_max_gust)

TWP/C2/SMET Wind Speeds

Beginning on December 24, Anemometer #1 (there are two anemometers on
the SMET stand) occasionally reported wind speed values that were low
relative to the other sensor.  It is clear from the data that the low
reading here is the anomalous one.

• Wind #1 speed minimum(wind1_spd_min)
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• wind1_dir_sd
• wind1_spd_sd
• Wind #1 speed maximum(wind1_spd_max)
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Wind #1 speed maximum gust(wind1_spd_max_gust)
• Wind #1 direction vector average(wind1_dir_vec_avg)

• Raw data stream - documentation not supported

• wind1_spd_sd
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• wind1_dir_sd
• Wind #1 speed maximum(wind1_spd_max)
• Wind #1 speed minimum(wind1_spd_min)
• Wind #1 direction vector average(wind1_dir_vec_avg)
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Wind #1 speed maximum gust(wind1_spd_max_gust)

TWP/C2/SMET Winds Speeds

Beginning on December 24, Anemometer #1 (there are two anemometers on
the SMET stand) occasionally reported wind speed values that were low
relative to the other sensor.  It is clear from the data that the low
reading here is the anomalous one.

• Wind #1 speed minimum(wind1_spd_min)
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• wind1_dir_sd
• wind1_spd_sd
• Wind #1 speed maximum(wind1_spd_max)
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Wind #1 speed maximum gust(wind1_spd_max_gust)
• Wind #1 direction vector average(wind1_dir_vec_avg)

• Raw data stream - documentation not supported

• wind1_spd_sd
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• wind1_dir_sd
• Wind #1 speed maximum(wind1_spd_max)
• Wind #1 speed minimum(wind1_spd_min)
• Wind #1 direction vector average(wind1_dir_vec_avg)
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Wind #1 speed maximum gust(wind1_spd_max_gust)

TWP/MWR/C2 - Installation

The Nauru ARCS was installed during the period September-November
1998.  Data were being collected by the end of October, but for the
first several weeks of November, the site was undergoing considerable
change, so data from that period should be used with caution.  The
official site dedication occured on November 20.  Most on-site
activity ended following the dedication so we will consider November
20 to be the beginning of the Nauru operations.  The last members of
the installation team left Nauru on November 24.

• bb23
• tipsky23
• bbn31
• tkair
• tkbb
• tnd_nom31
• tkxc
• actaz
• tnd31
• bbn23
• wet_window
• tc31
• r23
• tknd
• tnd23I
• bb31
• tc23
• tnd_nom23
• actel
• tnd23
• tnd31I
• r31
• tipsky31

• tnd_nom23
• Temperature, Sky Infra-Red(sky_ir_temp)
• tnd23
• sky23
• Total liquid water along LOS path(liq)
• bbn23
• bb31
• Temperature, brightness, longwave(ir_temp)
• actel
• wet_window
• tkbb
• tc23
• 23.8 GHz sky brightness temperature(tbsky23)
• 31.4 GHz sky brightness temperature(tbsky31)
• sky31
• tnd_nom31
• tkair
• tkxc
• Total water vapor along LOS path(vap)
• tknd
• tnd31
• bb23
• bbn31
• tc31
• actaz

TWP/C2/SMET Temperature spike

There was a brief -4 C spike in the temperature at approximately
21.5 Z on December 3.  This spike also showed up in the vapor pressure
which is calculated from the temperature and relative humidity.

• vappress_sd
• Temperature maximum(temp_max)
• temp_sd
• Vapor pressure mean(vappress_mean)
• Temperature minimum(temp_min)
• Temperature mean(temp_mean)

• Temperature mean(temp_mean)
• temp_sd
• Vapor pressure mean(vappress_mean)
• Temperature maximum(temp_max)
• vappress_sd
• Temperature minimum(temp_min)

TWP/C2/SMET - Pressure sensitivity to rain

The pressure behaves anomalously during rain events - even very mild
ones.  Normally, the pressure undergoes a smooth semi-diurnal
oscillation with little higher frequency variability.  However, during
and shortly after rain events, the pressure signal exhibits abrupt
changes - this sort of behavior has occasionally been observed at
Manus but not with the regularity seen here.  Examples of this
behaviour occur on (date in the form YYYYMMDD):

19981212
19981215
19981216
19981217
19981223
19981224
19981225
19981230
19981231

• vappress_sd
• Vapor pressure mean(vappress_mean)
• Atmospheric pressure(atmos_pressure)

• Atmospheric pressure(atmos_pressure)
• Vapor pressure mean(vappress_mean)
• vappress_sd

TWP/MWR/C2 - Excessive wet_window flags

The wet_window flag is set high more than expected from the measured value of liquid water 
path. This may be caused by dew or, if the heater sensivity is slightly misadjusted, by 
the diurnal variation in ambient temperature.

The "wet_window" flag is an indicator of moisture on the MWR window which invalidates the 
measurements of precipitable water vapor and liquid water path. Sometimes this flag can 
be incorrectly set high or low if the heater sensivity is slightly misadjusted. The heater 
adjustment is a resistive device that is dependent on ambient temperature. Another 
indicator of moisture on the window is unreasonably high ( > 3*liquid_retrieval_rms_accuracy ) 
values of "liq".

• wet_window

• wet_window

TWP/SMET/C2 - RH Sensor bad at Nauru

RH sensor bad from 16 Dec 2001 03 GMT to 3 Jan 2002

• relh_sd
• Relative humidity mean(relh_mean)
• Relative humidity maximum(relh_max)
• Relative humidity minimum(relh_min)

• relh_sd
• Relative humidity minimum(relh_min)
• Relative humidity mean(relh_mean)
• Relative humidity maximum(relh_max)

TWP/SMET/C1/C2 - Switch to new Data Header Formats not timely

On April 1, 2001 at 00:00:00 new data header with consistent variable naming conventions, 
etc were to be used for all sites, all data streams.  At the TWP sites the time of the 
movement to the new convention did not occur precisely at 00:00:00.  The following data 
files contain between 40 seconds and 20 minutes of data from 4/1/02 in the old format.  The 
delayed format change did not affect data quality in any way.

twpsmet60sC1.a1.20010401.000001.cdf
twpsmet60sC1.b1.20010401.000001.cdf
twpsmet60sC2.a1.20010401.000000.cdf
twpsmet60sC2.b1.20010401.000000.cdf

• lo_dir_vec_avg
• lo_spd_vec_avg
• up_spd_min
• up_spd_max
• Temperature mean(temp_mean)
• relh_sd
• temp_sd
• internal_voltage
• Atmospheric pressure(atmos_pressure)
• up_spd_vec_avg
• Precipitation mean(precip_mean)
• base_time
• logger_temp
• Precipitation maximum(precip_max)
• lon
• up_dir_vec_avg
• precip_sd
• lo_dir_sd
• Precipitation minimum(precip_min)
• vappress_sd
• Vapor pressure mean(vappress_mean)
• tbrg_count_total
• up_spd_arith_avg
• lat
• time_offset
• lo_spd_min
• tbrg_total
• lo_spd_max
• lo_spd_arith_avg
• up_dir_sd
• lo_spd_sd
• alt
• time
• Relative humidity mean(relh_mean)
• up_spd_sd

• up_dir_sd
• up_spd_max
• logger_temp
• time_offset
• up_spd_min
• Temperature mean(temp_mean)
• lo_spd_sd
• up_spd_sd
• tbrg_count_total
• lon
• lo_dir_vec_avg
• Precipitation maximum(precip_max)
• relh_sd
• internal_voltage
• base_time
• lo_spd_min
• Relative humidity mean(relh_mean)
• precip_sd
• tbrg_total
• temp_sd
• Vapor pressure mean(vappress_mean)
• up_spd_vec_avg
• up_dir_vec_avg
• lat
• lo_spd_max
• Atmospheric pressure(atmos_pressure)
• up_spd_arith_avg
• lo_spd_arith_avg
• lo_spd_vec_avg
• Precipitation minimum(precip_min)
• time
• alt
• vappress_sd
• Precipitation mean(precip_mean)
• lo_dir_sd

• Temperature mean(temp_mean)
• lat
• Wind #2 speed maximum gust(wind2_spd_max_gust)
• vappress_sd
• relh_sd
• time_offset
• Vapor pressure mean(vappress_mean)
• bit_data
• Wind #2 speed arithmetic average(wind2_spd_arith_avg)
• temp_sd
• internal_voltage
• Wind #2 speed maximum(wind2_spd_max)
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• alt
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Wind #2 speed vector average(wind2_spd_vec_avg)
• external_voltage
• Wind #1 speed minimum(wind1_spd_min)
• wind1_spd_sd
• wind2_dir_sd
• Temperature maximum(temp_max)
• Wind #1 direction vector average(wind1_dir_vec_avg)
• Atmospheric pressure(atmos_pressure)
• Temperature minimum(temp_min)
• Wind #2 speed minimum(wind2_spd_min)
• lon
• Precipitation maximum(precip_max)
• Wind #1 speed maximum(wind1_spd_max)
• Precipitation mean(precip_mean)
• precip_sd
• Wind #1 speed maximum gust(wind1_spd_max_gust)
• Precipitation minimum(precip_min)
• logger_temp
• Relative humidity mean(relh_mean)
• Relative humidity maximum(relh_max)
• wind2_spd_sd
• Wind #2 direction vector average(wind2_dir_vec_avg)
• base_time
• Relative humidity minimum(relh_min)
• wind1_dir_sd

• Precipitation mean(precip_mean)
• Wind #2 direction vector average(wind2_dir_vec_avg)
• wind2_spd_sd
• Wind #2 speed maximum gust(wind2_spd_max_gust)
• Wind #2 speed vector average(wind2_spd_vec_avg)
• temp_sd
• Wind #1 direction vector average(wind1_dir_vec_avg)
• precip_sd
• time_offset
• Temperature maximum(temp_max)
• internal_voltage
• Wind #2 speed minimum(wind2_spd_min)
• Atmospheric pressure(atmos_pressure)
• vappress_sd
• Relative humidity minimum(relh_min)
• Wind #2 speed arithmetic average(wind2_spd_arith_avg)
• lat
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• Precipitation minimum(precip_min)
• Temperature minimum(temp_min)
• Wind #2 speed maximum(wind2_spd_max)
• alt
• bit_data
• wind1_spd_sd
• logger_temp
• wind1_dir_sd
• base_time
• relh_sd
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Relative humidity mean(relh_mean)
• Wind #1 speed maximum gust(wind1_spd_max_gust)
• Relative humidity maximum(relh_max)
• Wind #1 speed minimum(wind1_spd_min)
• lon
• Precipitation maximum(precip_max)
• wind2_dir_sd
• Temperature mean(temp_mean)
• Wind #1 speed maximum(wind1_spd_max)
• Vapor pressure mean(vappress_mean)
• external_voltage

TWP/C2  Installation

The Nauru ARCS was installed during the period September-November
1998.  Data were being collected by the end of October, but for the
first several weeks of November, the site was undergoing considerable
change, so data from that period should be used with caution.  The
official site dedication occured on November 20.  Most on-site
activity ended following the dedication so we will consider November
20 to be the beginning of the Nauru operations.  The last members of
the installation team left Nauru on November 24.

• vappress_sd
• Wind #1 speed minimum(wind1_spd_min)
• wind1_dir_sd
• Vapor pressure mean(vappress_mean)
• wind1_spd_sd
• Temperature mean(temp_mean)
• Wind #2 direction vector average(wind2_dir_vec_avg)
• Wind #1 direction vector average(wind1_dir_vec_avg)
• lat
• time_offset
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• relh_sd
• temp_sd
• bit_data
• Temperature minimum(temp_min)
• internal_voltage
• Wind #2 speed minimum(wind2_spd_min)
• filename
• Wind #2 speed vector average(wind2_spd_vec_avg)
• Atmospheric pressure(atmos_pressure)
• Precipitation mean(precip_mean)
• Wind #1 speed maximum gust(wind1_spd_max_gust)
• wind2_dir_sd
• Relative humidity maximum(relh_max)
• Relative humidity minimum(relh_min)
• Temperature maximum(temp_max)
• Wind #2 speed arithmetic average(wind2_spd_arith_avg)
• base_time
• logger_temp
• Precipitation maximum(precip_max)
• lon
• Wind #2 speed maximum(wind2_spd_max)
• alt
• precip_sd
• Wind #1 speed maximum(wind1_spd_max)
• Wind #1 speed vector average(wind1_spd_vec_avg)
• external_voltage
• Precipitation minimum(precip_min)
• wind2_spd_sd
• Relative humidity mean(relh_mean)
• Wind #2 speed maximum gust(wind2_spd_max_gust)

• Raw data stream - documentation not supported

• Precipitation mean(precip_mean)
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• Wind #2 direction vector average(wind2_dir_vec_avg)
• Precipitation minimum(precip_min)
• Temperature minimum(temp_min)
• Wind #2 speed maximum(wind2_spd_max)
• wind2_spd_sd
• filename
• Wind #2 speed maximum gust(wind2_spd_max_gust)
• alt
• bit_data
• wind1_spd_sd
• logger_temp
• Wind #2 speed vector average(wind2_spd_vec_avg)
• wind1_dir_sd
• base_time
• temp_sd
• relh_sd
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Wind #1 direction vector average(wind1_dir_vec_avg)
• Relative humidity mean(relh_mean)
• Wind #1 speed maximum gust(wind1_spd_max_gust)
• Relative humidity maximum(relh_max)
• precip_sd
• time_offset
• Temperature maximum(temp_max)
• internal_voltage
• Wind #2 speed minimum(wind2_spd_min)
• Atmospheric pressure(atmos_pressure)
• Wind #1 speed minimum(wind1_spd_min)
• vappress_sd
• lon
• Precipitation maximum(precip_max)
• Relative humidity minimum(relh_min)
• wind2_dir_sd
• Temperature mean(temp_mean)
• Wind #1 speed maximum(wind1_spd_max)
• Vapor pressure mean(vappress_mean)
• Wind #2 speed arithmetic average(wind2_spd_arith_avg)
• lat
• external_voltage

TWP/SMET/C2 - Negative rainfall rates

Due to limitations of the Zeno dataloggers all voltage measurements
from the optical rain gauge (ORG) were converted to rainfall rates. 
This resulted in negative values for rain rates.  Any value below
0.10 mm/hr should be considered to be 0 mm/hr.  New dataloggers 
alleviated this problem.

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

TWP/MWR/C2 - software upgrade (version 3.29)

The MWR operating program was upgraded to version 3.29 on 30 July 1999. This version 
included a beam width correction as well as provided the capability to automatically level the 
elevation mirror (that is, to automatically detect and correct offsets in the elevation 
angle stepper motor position.)
   
The improvement in the quality of the tip curves resulting from the auto-leveling has been 
dramatic: differences in the brightness temperatures at 3 airmasses (19.5 and 160.5 
degrees) have been reduced from +/- 5 K to +/- 0.5 K. In order to take full advantage of this 
improvement to detect and reject cloudy tip curves, the minimum value of the 
goodness-of-fit coefficient for a valid tip curve has been increased from 0.995 to 0.998.

The data prior to July 30 1999 do not include beam-width and mirror-leveling corrections.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/SMET/C2 - Reprocess: Barometric pressure units change

Barometric pressure data during this time period is reported in hPa.  After this time, the 
data have been converted to kPa to standardize the measurement units among ARM sites and 
to conform to accepted standard units determined by the scientific community.

• Atmospheric pressure(atmos_pressure)

TWP/SMET/C2 - Reprocess: Tipping bucket rain gauge added

A tipping bucket rain gauge was added to the TWP.C2 SMET suite of instruments on 20061129. 
Effective 20060926, two new variables (count and rain amount) were added to the end of 
the twpsmet60sC2.b1 datastream.  Between 9/26 and 11/29, 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 19981021-20060926 and data from 
19981021-20061129 will be filled with -9999 (missing).

• base_time

TWP/MWR/C2 - Missing Data

Data are missing and unrecoverable.

• tnd_nom23
• Temperature, Sky Infra-Red(sky_ir_temp)
• tnd23
• lat
• sky23
• Total liquid water along LOS path(liq)
• lon
• bbn23
• time_offset
• bb31
• Temperature, brightness, longwave(ir_temp)
• actel
• wet_window
• tkbb
• tc23
• 23.8 GHz sky brightness temperature(tbsky23)
• sky31
• 31.4 GHz sky brightness temperature(tbsky31)
• tnd_nom31
• tkxc
• tkair
• tknd
• Total water vapor along LOS path(vap)
• bb23
• tnd31
• bbn31
• alt
• tc31
• actaz
• base_time

TWP/SMET/C2 - Missing data

Data are missing and unrecoverable.

• vappress_sd
• lo_spd_arith_avg
• lo_dir_vec_avg
• lo_spd_vec_avg
• Vapor pressure mean(vappress_mean)
• base_time
• up_spd_min
• up_dir_sd
• up_spd_max
• logger_temp
• Temperature mean(temp_mean)
• tbrg_count_total
• Precipitation maximum(precip_max)
• lon
• up_spd_arith_avg
• lo_spd_sd
• lat
• time_offset
• relh_sd
• lo_spd_min
• up_dir_vec_avg
• temp_sd
• alt
• internal_voltage
• precip_sd
• Atmospheric pressure(atmos_pressure)
• up_spd_vec_avg
• lo_dir_sd
• Precipitation minimum(precip_min)
• Precipitation mean(precip_mean)
• tbrg_total
• time
• Relative humidity mean(relh_mean)
• lo_spd_max
• up_spd_sd

TWP/SMET/C2 - 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_arith_avg
• lo_spd_min
• lo_spd_vec_avg
• up_spd_min
• up_spd_arith_avg
• lo_spd_max
• up_spd_max
• up_spd_sd
• lo_spd_sd
• up_spd_vec_avg

TWP/MWR/C2 - Software Change

The MWR operating software was changed on 19 November 1998 to provide additional 
functionality as described below.
   
NEW FEATURES
1. Faster sampling rate
   
Standard line-of-sight (LOS) observations can now be acquired at 15-second intervals vs. 
20-second intervals previously. (The standard LOS cycle is comprised of one sky sample per 
blackbody sample and gain update.)
   
2. More flexible sampling strategy
   
Multiple sky observations can be acquired during a LOS cycle, up to 1024 per gain update. 
This permits sky samples to be acquired at intervals of 2.67 seconds for improved 
temporal resolution of cloud liquid water variations and better coordination with the millimeter 
cloud radar during IOPs.
   
3. Separation of zenith LOS observations from TIP data
   
When the radiometer is in TIP mode, the zenith LOS observations are now extracted, the PWV 
and LWP computed and reported separately in the output file. This eliminates the periods 
of missing LOS data during calibration checks/updates.
   
4. Automatic self-calibration
   
The software now permits the calibration to be updated at specified intervals or 
continuously. In the first case, LOS mode is automatically changed to TIP mode at user-specified 
intervals or whenever clear sky conditions occur, the tip data reduced, the calibration 
updated, and the radiometer returned to LOS mode without operator intervention. In the 
second case, the radiometer is continuously is TIP mode until changed by the operator.
   
5. Graphical user display
   
The graphical display is comprised of a status display, a message display, a temperature 
plot, a plot of the retrieved PWV and LWP, and (in TIP mode) a plot of the latest tip 
curves.

• tnd23
• tkair
• tknd
• tnd31