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
• IR Brightness Temperature(sky_ir_temp)
• time_offset
• bb31
• Temperature, brightness, longwave(ir_temp)
• actel
• wet_window
• Radiation, longwave, brightness temperature, 23.8 GHz(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/Sonde Missing Data

There were no sondes launced during this period because there was
no helium on site and the hydrogen generator was not working.  The
hydrogen generator was repaired and launches resumed.

• Raw data stream - documentation not supported

• Raw data stream - documentation not supported

• lat
• base_time
• Eastward Wind Component(u_wind)
• Northward Wind Component(v_wind)
• wstat
• Dry Bulb Temperature(tdry)
• Mean Wind Speed(wspd)
• Wind Direction(deg)
• alt
• Dewpoint Temperature(dp)
• asc
• Humidity, relative(rh)
• lon
• time_offset
• Pressure, atmospheric, constant value of model level, RUC model output(pres)

• lon
• Pressure, atmospheric, constant value of model level, RUC model output(pres)
• wstat
• Dewpoint Temperature(dp)
• Humidity, relative(rh)
• alt
• asc
• base_time
• time_offset
• Wind Direction(deg)
• lat
• Mean Wind Speed(wspd)
• Dry Bulb Temperature(tdry)

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
• IR Brightness Temperature(sky_ir_temp)
• tnd23
• sky23
• Total liquid water along LOS path(liq)
• bbn23
• bb31
• Temperature, brightness, longwave(ir_temp)
• actel
• wet_window
• tkbb
• tc23
• Radiation, longwave, brightness temperature, 23.8 GHz(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/SONDE/C2 - Missing Winds

About half of the soundings in November-December exhibited drop-outs
in the winds.  These dropouts were typically over a depth of 1-2 km.
Sometimes the dropout occurred at the surface, sometimes at the top of
the sounding and sometimes in the middle.  These gaps occurred on:

19981126
19981129
19981206
19981209
19981210
19981211
19981212
19981221
19981222

• Mean Wind Speed(wspd)
• Eastward Wind Component(u_wind)
• Northward Wind Component(v_wind)

• Mean Wind Speed(wspd)

TWP/C2/Balloon Soundings: Missing Flights

No sondes were launched during this period for reasons unknown.

• lat
• base_time
• Eastward Wind Component(u_wind)
• Northward Wind Component(v_wind)
• wstat
• Dry Bulb Temperature(tdry)
• Mean Wind Speed(wspd)
• Wind Direction(deg)
• alt
• Dewpoint Temperature(dp)
• asc
• Humidity, relative(rh)
• lon
• time_offset
• Pressure, atmospheric, constant value of model level, RUC model output(pres)

• lon
• Pressure, atmospheric, constant value of model level, RUC model output(pres)
• wstat
• Dewpoint Temperature(dp)
• Humidity, relative(rh)
• alt
• asc
• base_time
• time_offset
• Wind Direction(deg)
• lat
• Mean Wind Speed(wspd)
• Dry Bulb Temperature(tdry)

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/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.

• Raw data stream - documentation not supported

• lat
• base_time
• Eastward Wind Component(u_wind)
• Northward Wind Component(v_wind)
• wstat
• Dry Bulb Temperature(tdry)
• Mean Wind Speed(wspd)
• Wind Direction(deg)
• alt
• Dewpoint Temperature(dp)
• asc
• Humidity, relative(rh)
• lon
• time_offset
• Pressure, atmospheric, constant value of model level, RUC model output(pres)

• lon
• Pressure, atmospheric, constant value of model level, RUC model output(pres)
• wstat
• Dewpoint Temperature(dp)
• Humidity, relative(rh)
• alt
• asc
• base_time
• time_offset
• Wind Direction(deg)
• lat
• Mean Wind Speed(wspd)
• Dry Bulb Temperature(tdry)

TWP/SONDE/C2  - Broken Temperature Sensor

The temperature sensors on these radiosondes broke at launch.  All
the temperature-related data are incorrect.

• Dry Bulb Temperature(tdry)
• Dewpoint Temperature(dp)
• Humidity, relative(rh)

• Humidity, relative(rh)
• Dewpoint Temperature(dp)
• Dry Bulb Temperature(tdry)

TWP/SONDE/C2 - Bad RH Data (AIRS Validation Sonde)

The RH sensor heating circuit failed on this sonde.  This results in
oscillation of reported RH between reasonable values and values near zero.
This was an AIRS validation sounding.

• Dewpoint Temperature(dp)
• Humidity, relative(rh)

• Humidity, relative(rh)
• Dewpoint Temperature(dp)

TWP/SONDE/C2  - Failure of RH sensor

It appears that the RH sensor heating circuit failed during this sounding.  The RH 
oscillates rapidly between low (~0 %RH) and not so low (ambient %RH) and the oscillation seems 
to stop when the temperature is below ~35 degC.  According to Vaisala these are symptoms 
of failure in the ASIC (application specific integrated circuit) that controls the heating.

• Dewpoint Temperature(dp)
• Humidity, relative(rh)

• Humidity, relative(rh)
• Dewpoint Temperature(dp)

TWP/SONDE/C2 - Strange problem with data -

This is very strange.  The data has what appears to be a pressure jump at launch (from 
1007.2 to 956.5 hPa) but the sounding temperature and RH data clearly look to be 
interpolated between the surface and tropopause.  By examining the absolutely raw data, I found that 
the system assigned an elapsed time of 408 seconds (since system start up) to the launch 
point, but there is no raw data between 410 and 532 seconds.  The raw pressure value at 
410 seconds is 1007.6 hPa and that at 532 seconds is 40.9 hPa!  Unless this sounding was 
done by using a rocket-powered balloon (maybe even then), it would be impossible for the 
sonde to get to 40.9 hPa in 2 minutes.  Because the apparent gap is only two minutes, the 
system was able to interpolate but is not sophisticated enough to understand that the 
limits of the interpolation are unreasonable.

I can't imagine what went wrong - I've not seen anything like this before.

• Raw data stream - documentation not supported

• Raw data stream - documentation not supported

• lon
• Eastward Wind Component(u_wind)
• Northward Wind Component(v_wind)
• asc
• Humidity, relative(rh)
• time_offset
• base_time
• Dewpoint Temperature(dp)
• wstat
• Wind Direction(deg)
• alt
• Mean Wind Speed(wspd)
• Pressure, atmospheric, constant value of model level, RUC model output(pres)
• lat
• Dry Bulb Temperature(tdry)

TWP/SONDE/C2 - RH sensor bad

It appears that the RH sensor heating circuits failed during these
soundings.  The RH oscillates rapidly between low (~0 %RH) and not
so low (ambient %RH) and the oscillation seems to stop when the
temperature is below ~35 degC.  According to Vaisala these are
symptoms of failure in the ASIC (application specific integrated
circuit) that controls the heating.

• Humidity, relative(rh)
• Dewpoint Temperature(dp)

TWP/SONDE/C2 - Broken temperature sensors

The temperature sensors on these radiosondes broke after launch.  All
temperature-related data are incorrect.

• Humidity, relative(rh)
• Dewpoint Temperature(dp)
• Dry Bulb Temperature(tdry)

TWP/SONDE/C2  - Questionable rH data

It appears that the RH sensor heating circuit failed during this sounding.  The RH 
oscillates rapidly between low (~0 %RH) and not so low (ambient %RH) and the oscillation seems 
to stop when the temperature is below ~35 degC.  According to Vaisala these are symptoms 
of failure in the ASIC (application specific integrated circuit) that controls the heating.

• Humidity, relative(rh)
• Dewpoint Temperature(dp)

TWP/MWR/C2 - thermal instability

The MWR required an unusually long time to reach thermal stability after a 4-day outage 
due to a power failure that damaged the blower/heater assembly. Also during this period, 
the heater, which had been replaced, appears to have been on continously, causing the data 
to be inappropriately flagged.

• tipsky23
• tc23
• tnd_nom23
• tnd_nom31
• wet_window
• tc31
• tipsky31

• tnd_nom23
• sky31
• 31.4 GHz sky brightness temperature(tbsky31)
• sky23
• tnd_nom31
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• tc31
• wet_window
• tc23
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

TWP/SONDE/C2  - Bad RH sensor

It appears that the RH sensor heating circuit failed during this sounding.  The RH 
oscillates rapidly between low (~0 %RH) and not so low (ambient %RH) and the oscillation seems 
to stop when the temperature is below ~35 degC.  According to Vaisala these are symptoms 
of failure in the ASIC (application specific integrated circuit) that controls the heating.

• Humidity, relative(rh)
• Dewpoint Temperature(dp)

TWP/SONDE/C2 - Bad RH values aloft

It appears that the RH sensor heating circuit on this sonde failed about 24 minutes into 
the flight.  The RH values look reasonable, though somewhat noisy, from the surface to 
approximately 6.9 km (439 hPa) at which point they begin to oscillate between 0 and 100 %.  
This behavior stops when the sonde reaches approximately 11.5km (232 hPa) when the air 
temperature drops below -40 degC.  The oscillation stops at that point, though the RH 
remains higher than might be expected even under supersaturated conditions.

• Humidity, relative(rh)
• Dewpoint Temperature(dp)

TWP/SONDE/C2  - RH sensor failure near surface

It appears that the RH sensor heating circuit failed during this sounding.  The RH 
oscillates rapidly between low (~0 %RH) and not so low (ambient %RH) and the oscillation seems 
to stop when the temperature is below ~35 degC.  According to Vaisala these are symptoms 
of failure in the ASIC (application specific integrated circuit) that controls the heating.

• Humidity, relative(rh)
• Dewpoint Temperature(dp)

TWP/SONDE/C2 - Operator used wrong calibration tape

It appears as though the opperator used the wrong calibration tape for this sounding.  The 
primary symptom is a jump in temperature from a surface value of 30.1 degC to the first 
value aloft of 61.0 degC.  Secondly, the recorded serial number for this sounding is 
Z1430179 which is the same serial number recorded for the previous sounding.

This problem points to three failures of procedure (I have notified TWP site ops by 
e-mail).  The first failure is using the wrong tape. The second failure is not checking the 
radiosonde values before launch which relates to the third failure of not entering the 
radiosonde values as the surface values of the sounding.

• lon
• Eastward Wind Component(u_wind)
• Northward Wind Component(v_wind)
• asc
• Humidity, relative(rh)
• time_offset
• base_time
• Dewpoint Temperature(dp)
• wstat
• Wind Direction(deg)
• alt
• Mean Wind Speed(wspd)
• Pressure, atmospheric, constant value of model level, RUC model output(pres)
• lat
• Dry Bulb Temperature(tdry)

TWP/MWR/C2 - Data collection problem

Large, frequent data gaps occurred due to a failing laptop computer. The problem was 
corrected when a new computer was installed.

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

• Raw data stream - documentation not supported

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

TWP/SONDE/C2  - RH sensor failure below 9km

It appears that the RH sensor heating circuit failed during this sounding.  The RH 
oscillates rapidly between low (~0 %RH) and not so low (ambient %RH) and the oscillation seems 
to stop when the temperature is below ~35 degC.  According to Vaisala these are symptoms 
of failure in the ASIC (application specific integrated circuit) that controls the heating.

• Humidity, relative(rh)
• Dewpoint Temperature(dp)

TWP/SONDE/C2 - Bad RH values aloft

It appears that the RH sensor heating circuit on these sondes failed after launch but 
resume proper operation when the ambient temperature dropped below ~40 degC.

• Humidity, relative(rh)
• Dewpoint Temperature(dp)

TWP/MWR/C2 - Reprocessed: Revised Retrieval Coefficients

IN THE BEGINNING (June 1992), the retrieval coefficients used to derive the precipitable 
water vapor (PWV) and liquid water path (LWP) from the MWR brightness temperatures were 
based on the Liebe and Layton (1987) water vapor and oxygen absorption model and the Grant 
(1957) liquid water absorption model.

Following the SHEBA experience, revised retrievals based on the more recent Rosenkranz 
(1998) water vapor and oxygen absorption models and the Liebe (1991) liquid waer absorption 
model were developed.  The Rosenkranz water vapor absorption model resulted a 2 percent 
increase in PWV relative to the earlier Liebe and Layton model.  The Liebe liquid water 
absorption model decreased the LWP by 10% relative to the Grant model.  However, the 
increased oxygen absorption caused a 0.02-0.03 mm (20-30 g/m2) reduction in LWP, which was 
particularly significant for low LWP conditions (i.e. thin clouds encountered at SHEBA).

Recently, it has been shown (Liljegren, Boukabara, Cady-Pereira, and Clough, TGARS v. 43, 
pp 1102-1108, 2005) that the half-width of the 22 GHz water vapor line from the HITRAN 
compilation, which is 5 percent smaller than the Liebe and Dillon (1969) half-width used in 
Rosenkranz (1998), provided a better fit to the microwave brightness temperature 
measurements at 5 frequencies in the range 22-30 GHz, and yielded more accurate retrievals. 
Accordingly, revised MWR retrieval coefficients have been developed using MONORTM, which 
utilizes the HITRAN compilation for its spectroscopic parameters.  These new retrievals 
provide 3 percent less PWV and 2.6 percent greater LWP than the previous 
retrievals based on Rosenkranz (1998).

The Rosenkranz-based retrieval coefficients became active at TWP.C2 20020427.0600.  The 
MONORTM-based retrieval coefficients became active at TWP.C2 20050630.2100.

Note: The TWP.C2 data for 19981028-20050630 have been reprocessed to apply the 
MONORTM-based retrievals for all time.  The reprocessed data were archived 20061003.

• mean_vap_mwr
• mean_liq_mwr

• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)

• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)

TWP/MWR/C2 - New software version (4.15) installed

A problem began with the installation of MWR.EXE version 4.12 in November 2002. The 
software had been upgraded from a "DOS" to a "Windows"-compiled program to address an earlier 
problem.  The software upgrade corrected the earlier problem but introduced a new one that 
caused line-of-sight observing cycles to be skipped, a 15% reduction in the number of 
tip curves, and saturation of CPU usage.  Software versions 4.13 and 4.14 also produced 
these problems.

The new MWR software version (4.15) was installed on 9/15/2005. As a consequence of this 
upgrade, the tip curve frequency increased. The tip cycle time decreased from ~60s to ~50s.

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

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

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)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

TWP/MWR/C2 - Missing Data

Data are missing and unrecoverable.

• tnd_nom23
• IR Brightness Temperature(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
• Radiation, longwave, brightness temperature, 23.8 GHz(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/SONDE/C2 - Failure of RH sensor

The RH sensor ASIC that controls the sensor heating failed.  As a result the RH at the 
beginning of the sounding oscillates between near-zero and ambient values.  The RH heating 
cycle stops when the ambient temperature reaches below -30 degC; above this level RH 
values should be valid.

• Humidity, relative(rh)
• Dewpoint Temperature(dp)

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