NSA/MWR/C2 - incorrect flagging of data

The wet window flag is set high more frequent than expected.

• Water on Teflon window (1=WET, 0=DRY)(wet_window)

• Water on Teflon window (1=WET, 0=DRY)(wet_window)

• Water on Teflon window (1=WET, 0=DRY)(wet_window)

NSA/MWR/C2 - elevated sky brightness temperatures

The MWR was providing unreasonable values of sky brightness temperatures 
and values of precipitable water vapor and liquid water path that were
about 10 times larger than expected. The problem was corrected when the 
instrument was power-cycled. The cause of the problem is unknown.

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

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

• 31.4 GHz sky signal(tipsky31)
• 23.8 GHz sky signal(tipsky23)

NSA/MWR/C2 - Intermittent Negative Sky Brightness Temperatures

Several related and recurring problems with the MWRs have been reported
dating back to 1999.  These problems were due to the occurrence of
blackbody signals (in counts) that were half of those expected. The
symptoms included noisy data, spikes in the data, negative brightness
temperatures, and apparent loss of serial communication between the
computer and the radiometer, which results in a self-termination of the
MWR program.

Because these all initially appeared to be hardware-related problems,
the instrument mentor and site operations personnel (1) repeatedly
cleaned and replaced the fiber optic comm. components, (2) swapped
radiometers, (3) sent radiometers back to Radiometrics for evaluation
(which did not revealed any instrument problems), and (4) reconfigured
the computer's operating system.  Despite several attempts to isolate
and correct it, the problem persisted.

It became apparent that some component of the Windows98 configuration
conflicted with the DOS-based MWR program or affected the serial port
or the contents of the serial port buffer. This problem was finally
corrected by upgrading the MWR software with a new Windows-compatible
program.

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

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

NSA/MWR/C2  - min/max/delta values incorrect

The values of valid_min, valid_max, and valid_delta for fields tkxc and tknd were 
incorrect. They should be 303, 333, and 0.5 K, respectively.

• Mixer kinetic (physical) temperature(tkxc)
• Noise diode mount temperature(tknd)

NSA/MWR/C2 - Heater problem

The MWR heater did not appear to operate when moisture was present. The heater sensitivity 
was adjusted.

• Water on Teflon window (1=WET, 0=DRY)(wet_window)

• Water on Teflon window (1=WET, 0=DRY)(wet_window)

• Water on Teflon window (1=WET, 0=DRY)(wet_window)

NSA/MWR/C2 - no air temperature signal

When the new blower was upgraded by Radiometrics and reinstalled on the MWR, the air 
temperature sensor failed to properly report. It was determined that the wires carrying the 
signal to the analog board did not conform to the standard expected by the upgraded blower. 
The problem was corrected by modifying the MWR software to read the signal from the 
appropriate corresponding channel.

• Ambient temperature(tkair)

• Ambient temperature(tkair)

NSA/MWR/C2 - Reprocess: 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).

Although the MWR data will be reprocessed to apply the new monortm-based 
retrievals, for most purposes it will be sufficient to correct the data 
using the following factors:

PWV_MONORTM = 0.9695 * PWV_ROSENKRANZ
LWP_MONORTM = 1.026  * LWP_ROSENKRANZ

The Rosenkranz-based retrieval coefficients became active at NSA.C2 
20020418.1700.  The MONORTM-based retrieval coefficients became active 
at NSA.C2 20050629.0000.

Note: a reprocessing effort is already underway to apply the 
Rosenkranz-based retrieval coefficients to all MWR prior to April 
2002.  An additional reprocessing task will be undertaken to apply 
the MONORTM retrieval to all MWR data when the first is completed. 
Read reprocessing comments in the netcdf file header carefully to 
ensure you are aware which retrieval is in play.

• Mean total liquid water amount along LOS path(liq)
• Mean total water vapor amount along LOS path(vap)

• Mean total liquid water amount along LOS path(liq)
• Mean total water vapor amount along LOS path(vap)

• Total liquid water along zenith path using tip-derived brightness temperatures(liqtip)
• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)

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

A problem began with the installation of MWR.EXE version 4.12 in September 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.

• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• 23.8 GHz sky signal(sky23)
• 23.8 GHz Blackbody signal(bb23)
• Mean 23.8 GHz sky brightness temperature(tbsky23)
• 23.8 GHz blackbody+noise injection signal(bbn23)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Mixer kinetic (physical) temperature(tkxc)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• 31.4 GHz blackbody+noise injection signal(bbn31)
• Mean total liquid water amount along LOS path(liq)
• Mean IR brightness temperature(ir_temp)
• Blackbody kinetic temperature(tkbb)
• Mean total water vapor amount along LOS path(vap)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Ambient temperature(tkair)
• Temperature correction coefficient at 31.4 GHz(tc31)
• Temperature correction coefficient at 23.8 GHz(tc23)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• Noise diode mount temperature(tknd)
• 31.4 GHz sky signal(sky31)
• Sky/Cloud Infra-Red Temperature(sky_ir_temp)
• 31.4 GHz Blackbody signal(bb31)

• 23.8 GHz blackbody+noise injection signal(bbn23)
• 31.4 GHz sky signal(tipsky31)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• Noise injection temp at 31.4 GHz derived from this tip(tnd31I)
• Noise injection temp at 23.8 GHz derived from this tip(tnd23I)
• 31.4 GHz goodness-of-fit coefficient(r31)
• 31.8 GHz sky brightness temperature derived from tip curve(tbskytip31)
• Ambient temperature(tkair)
• 23.8 GHz sky brightness temperature derived from tip curve(tbskytip23)
• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)
• 23.8 GHz sky signal(tipsky23)
• Mixer kinetic (physical) temperature(tkxc)
• 31.4 GHz blackbody+noise injection signal(bbn31)
• 31.4 GHz Blackbody signal(bb31)
• Noise diode mount temperature(tknd)
• Temperature correction coefficient at 23.8 GHz(tc23)
• 23.8 GHz goodness-of-fit coefficient(r23)
• Blackbody kinetic temperature(tkbb)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• Total liquid water along zenith path using tip-derived brightness temperatures(liqtip)
• 23.8 GHz Blackbody signal(bb23)
• Temperature correction coefficient at 31.4 GHz(tc31)