NSA/MWR/C1 - negative sky brightness temperatures

The data exhibit occasional negative sky brightness temperatures.
The problem was corrected when the site operator cleaned the cable connectors and coated 
the terminals with dielectric grease.

• MWR column precipitable water vapor(vap)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• Averaged total liquid water along LOS path(liq)
• Mixer kinetic (physical) temperature(tkxc)
• Sky brightness temperature at 23.8 GHz(tbsky23)

• Sky brightness temperature at 23.8 GHz(tbsky23)
• MWR column precipitable water vapor(vap)
• Averaged total liquid water along LOS path(liq)
• Sky brightness temperature at 31.4 GHz(tbsky31)

NSA/MWR/C1 - negative sky brightness temperatures

The data exhibit occasional negative sky brightness temperatures.
The problem was corrected when the computer was reconfigured following a virus infection.

• MWR column precipitable water vapor(vap)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• Averaged total liquid water along LOS path(liq)
• Mixer kinetic (physical) temperature(tkxc)
• Sky brightness temperature at 23.8 GHz(tbsky23)

• Sky brightness temperature at 23.8 GHz(tbsky23)
• MWR column precipitable water vapor(vap)
• Averaged total liquid water along LOS path(liq)
• Sky brightness temperature at 31.4 GHz(tbsky31)

NSA/MWR/C1 - Reprocess: calibration change

The thicker (1/2-inch) insulation was installed on the RF deck and the reference 
temperature was reduced from 50 C to 30 C to prevent thermal instability in winter. A change in 
the mixer temperature affects the instrument's calibration. A new calibration was 
automatically derived and applied after 1500 valid tip curves were acquired. During the period 
after the temperature was reset and before the calibration was updated, the previous 
calibration was used.

• MWR column precipitable water vapor(vap)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• Averaged total liquid water along LOS path(liq)
• Sky brightness temperature at 23.8 GHz(tbsky23)

• Sky brightness temperature at 23.8 GHz(tbsky23)
• MWR column precipitable water vapor(vap)
• Averaged total liquid water along LOS path(liq)
• Sky brightness temperature at 31.4 GHz(tbsky31)

NSA/MWR/C1 - incorrect flagging of data

The wet window flag is set high more 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/C1 - 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 - Wet-window flag incorrectly set

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

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

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

NSA/MWR/C1 - NSA Barrow MWR down due to PC Virus

On 12/22 at 23:00 the PC communication hung. Before operators returned to work after the 
holidays on 12/26, the virus W32.kriz triggered on 12/25 at 1:43 GMT. This virus wiped out 
large amount of files, hereunder the data files from the period 12/22 23:00 - 12/25 
01:00 and OS system files. The fixed PC was re-installed on 1/5, due issues with using serial 
ports under DOS comunication with instrument was not restored until 1/9 @ 22:30 GMT

• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• 23.8 GHz sky signal(sky23)
• IR Brightness Temperature(ir_temp)
• Sky brightness temperature at 23.8 GHz(tbsky23)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• 31.4 GHz sky signal(sky31)
• 23.8 GHz blackbody+noise injection signal(bbn23)
• MWR column precipitable water vapor(vap)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• Temperature correction coefficient at 23.8 GHz(tc23)
• Temperature correction coefficient at 31.4 GHz(tc31)
• Ambient temperature(tkair)
• Blackbody kinetic temperature(tkbb)
• lon(lon)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Dummy altitude for Zeb(alt)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• Mixer kinetic (physical) temperature(tkxc)
• Averaged total liquid water along LOS path(liq)
• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• 31.4 GHz blackbody(bb31)
• base time(base_time)
• Time offset of tweaks from base_time(time_offset)
• (tknd)
• 31.4 GHz blac2body+noise injection signal(bbn31)
• lat(lat)
• 23.8 GHz Blackbody signal(bb23)

• Blackbody temperature 1(tkbb1)
• 31.4 GHz noise diode calib (injection temp) at Tkxc(ndiode31)
• 31.4 GHz calibration curve slope(gain31)
• Dummy altitude for Zeb(alt)
• base time(base_time)
• 31.4 GHz noise diode calib adjusted to tknd_nom and low_pass filtered(expave31)
• Actual elevation angle(actel)
• Tip configuration number(tipn)
• 23.8 GHz goodness-of-fit coefficient(r23)
• 31.4 GHz calibration curve offset(tbzenith31)
• 23.8 GHz noise diode calib adjusted to tknd_nom and low_pass filtered(expave23)
• IR Brightness Temperature(ir_temp)
• 31.4 GHz blac2body+noise injection signal(bbn31)
• lon(lon)
• 23.8 GHz blackbody signal(tipbb23)
• 31.4 GHz sky signal(tipsky31)
• 31.4 GHz blackbody(bb31)
• 23.8 GHz sky signal(tipsky23)
• 31.4 GHz sky signal+noise injection signal(tipskynd31)
• Blackbody temperature 2(tkbb2)
• 23.8 GHz calibration curve slope(gain23)
• Actual Azimuth(actaz)
• (tknd)
• Time offset of tweaks from base_time(time_offset)
• 23.8 GHz Blackbody signal(bb23)
• (tair)
• 31.4 GHz goodness-of-fit coefficient(r31)
• 23.8 GHz noise diode calib (injection temp) at Tkxc(ndiode23)
• lat(lat)
• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• 31.4 GHz blackbody signal(tipbb31)
• 23.8 GHz blackbody+noise injection signal(bbn23)
• 23.8 GHz sky signal+noise injection signal(tipskynd23)
• Mixer kinetic (physical) temperature(tkxc)
• Airmass value(airm)
• 23.8 GHz calibration curve offset(tbzenith23)

• IR Brightness Temperature(ir_temp)
• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• lat(lat)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• base time(base_time)
• MWR column precipitable water vapor(vap)
• Time offset of tweaks from base_time(time_offset)
• lon(lon)
• Averaged total liquid water along LOS path(liq)
• Dummy altitude for Zeb(alt)
• Sky brightness temperature at 23.8 GHz(tbsky23)

• (tknd)
• 23.8 GHz sky signal(tipsky23)
• Actual elevation angle(actel)
• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• Actual Azimuth(actaz)
• 23.8 GHz goodness-of-fit coefficient(r23)
• Temperature correction coefficient at 31.4 GHz(tc31)
• lon(lon)
• 31.4 GHz goodness-of-fit coefficient(r31)
• Ambient temperature(tkair)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• Dummy altitude for Zeb(alt)
• 31.4 GHz blackbody(bb31)
• lat(lat)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• Mixer kinetic (physical) temperature(tkxc)
• 31.4 GHz sky signal(tipsky31)
• Noise injection temp at 23.8 GHz derived from this tip(tnd23I)
• Noise injection temp at 31.4 GHz derived from this tip(tnd31I)
• 31.4 GHz blac2body+noise injection signal(bbn31)
• 23.8 GHz blackbody+noise injection signal(bbn23)
• base time(base_time)
• Temperature correction coefficient at 23.8 GHz(tc23)
• Time offset of tweaks from base_time(time_offset)
• 23.8 GHz Blackbody signal(bb23)
• Blackbody kinetic temperature(tkbb)

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.

• Sky brightness temperature at 31.4 GHz(tbsky31)
• Sky brightness temperature at 23.8 GHz(tbsky23)
• Averaged total liquid water along LOS path(liq)
• MWR column precipitable water vapor(vap)

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

NSA/MWR/C2 - Missing data

Data are missing and unrecoverable.

• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• base time(base_time)
• lat(lat)
• Mixer kinetic (physical) temperature(tkxc)
• lon(lon)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• Averaged total liquid water along LOS path(liq)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Ambient temperature(tkair)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• 31.4 GHz sky signal(sky31)
• Dummy altitude for Zeb(alt)
• Sky Infra-Red Temperature(sky_ir_temp)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• 23.8 GHz sky signal(sky23)
• 23.8 GHz Blackbody signal(bb23)
• Sky brightness temperature at 23.8 GHz(tbsky23)
• 23.8 GHz blackbody+noise injection signal(bbn23)
• 31.4 GHz blac2body+noise injection signal(bbn31)
• Time offset of tweaks from base_time(time_offset)
• Blackbody kinetic temperature(tkbb)
• MWR column precipitable water vapor(vap)
• IR Brightness Temperature(ir_temp)
• Temperature correction coefficient at 31.4 GHz(tc31)
• Temperature correction coefficient at 23.8 GHz(tc23)
• (tknd)
• 31.4 GHz blackbody(bb31)

• 23.8 GHz blackbody+noise injection signal(bbn23)
• Actual elevation angle(actel)
• Noise injection temp at 23.8 GHz derived from this tip(tnd23I)
• lon(lon)
• 31.8 GHz sky brightness temperature derived from tip curve(tbskytip31)
• Ambient temperature(tkair)
• Actual Azimuth(actaz)
• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)
• 31.4 GHz blackbody(bb31)
• (tknd)
• 23.8 GHz goodness-of-fit coefficient(r23)
• Dummy altitude for Zeb(alt)
• 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)
• lat(lat)
• Temperature correction coefficient at 31.4 GHz(tc31)
• 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)
• 31.4 GHz goodness-of-fit coefficient(r31)
• 23.8 GHz sky brightness temperature derived from tip curve(tbskytip23)
• Mixer kinetic (physical) temperature(tkxc)
• 23.8 GHz sky signal(tipsky23)
• 31.4 GHz blac2body+noise injection signal(bbn31)
• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• Blackbody kinetic temperature(tkbb)
• Temperature correction coefficient at 23.8 GHz(tc23)
• base time(base_time)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Time offset of tweaks from base_time(time_offset)

NSA/MWR/C1 - Data spikes, possibly due to cleaning events

Unreasonable spikes occurred, which may be due to cleaning of 
the instrument by the operator.  Other cleaning events did
not result in obvious data spikes and have not been included 
in this report.

• MWR column precipitable water vapor(vap)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• Averaged total liquid water along LOS path(liq)
• Sky brightness temperature at 23.8 GHz(tbsky23)

• Sky brightness temperature at 23.8 GHz(tbsky23)
• MWR column precipitable water vapor(vap)
• Averaged total liquid water along LOS path(liq)
• Sky brightness temperature at 31.4 GHz(tbsky31)

SGP/MWR/C1 - 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.

• MWR column precipitable water vapor(vap)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• Averaged total liquid water along LOS path(liq)
• Sky brightness temperature at 23.8 GHz(tbsky23)

• Sky brightness temperature at 23.8 GHz(tbsky23)
• MWR column precipitable water vapor(vap)
• Averaged total liquid water along LOS path(liq)
• Sky brightness temperature at 31.4 GHz(tbsky31)

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.

• Sky brightness temperature at 31.4 GHz(tbsky31)
• Sky brightness temperature at 23.8 GHz(tbsky23)
• Averaged total liquid water along LOS path(liq)
• MWR column precipitable water vapor(vap)

NSA/MWR/C1 - 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)
• (tknd)

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

Note: The NSA.C2 MWRLOS data for 19991018-20050630 have been reprocessed
to apply the MONORTM-based retrievals for all time. The reprocessed data
were archived in March 2007.  The TIP data have not been reprocessed.

• Averaged total liquid water along LOS path(liq)
• MWR column precipitable water vapor(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)