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 - 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