NSA/MWR/C1 - Temperature Stabilization of Noise Diode Impaired

On 1/17 we had a big spike in the data and lost temperature stabilization. The instrument 
had problems maintaining the Noise Diode (ND) temperature since. At ambient temperatures 
under about -20 C the ND was not maintaining the set temperature of 30 C. This problem 
was reported in P010122.1.

Fred Solheim recommended on 1/22 that we powercycle the instrument as it looked like the 
instrument CPU had lost the temperature reference.

So we powercycled the instrument on 1/22 @ 20:30 and lost all comumnication to it; after a 
second powercycling the instrument came back on line and the temperature stabilized 
quickly (within a couple of minutes) to the set temperature (30 C)

Fred Solheim reported after the system was restored:
"I've never seen this behavior before. I don't think it was due to the RF deck physically 
hanging temperature, because the recorded temp dropped about 30 C in one observation 
cycle. If this happens again, send the MWR down along with data files for us to look at."

Data collected in the periode 1/17/2001 6:00 to 1/22/2001 21:45 are questionable since it 
is uncertain whether the temperature really was unstable and what really caused the 
problem.

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

• Sky brightness temperature at 23.8 GHz(tbsky23)
• Standard deviation about the mean for the IR brightness temperature(ir_temp_sdev)
• Number of points included in the ir_temp ensemble(num_obs_irt)
• Standard deviation about the mean for the 23.8 GHz sky brightness temperature(tbsky23_sdev)
• Fraction of data in averaging interval with water on Teflon window(water_flag_fraction)
• IR Brightness Temperature(ir_temp)
• Standard deviation about the mean for the 31.4 GHz sky brightness temperature(tbsky31_sdev)
• Standard deviation about the mean for the total liquid water amount(liq_sdev)
• Number of data points averaged for 23tbsky, 31tbsky, vap & liq(num_obs)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• MWR column precipitable water vapor(vap)
• Averaged total liquid water along LOS path(liq)
• Standard deviation about the mean for the total water vapor amount(vap_sdev)

• MWR column precipitable water vapor(vap)
• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• Averaged total liquid water along LOS path(liq)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• IR Brightness Temperature(ir_temp)
• Sky brightness temperature at 23.8 GHz(tbsky23)

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 - Reprocess: calibration change

The computer was replaced but not configured correctly for the MWR.

• Temperature correction coefficient at 31.4 GHz(tc31)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• Averaged total liquid water along LOS path(liq)
• Sky brightness temperature at 23.8 GHz(tbsky23)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• MWR column precipitable water vapor(vap)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• Temperature correction coefficient at 23.8 GHz(tc23)

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

• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Temperature correction coefficient at 31.4 GHz(tc31)
• Temperature correction coefficient at 23.8 GHz(tc23)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• 23.8 GHz sky signal(tipsky23)
• 31.4 GHz sky signal(tipsky31)

NSA/MWR/C1 - Reprocess: wrong calibration

Moisture was found inside the lens of the MWR. Removal of the moisture caused a 
significant change in the calibration, especially in the 23.8 GHz channel. The calibration was 
updated automatically.

• 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 - Instrument Maintenance

Exchange of winter cover caused data corruption.

• Sky brightness temperature at 31.4 GHz(tbsky31)
• 23.8 GHz sky signal(sky23)
• 31.4 GHz sky signal(sky31)
• Sky brightness temperature at 23.8 GHz(tbsky23)
• Averaged total liquid water along LOS path(liq)
• MWR column precipitable water vapor(vap)

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)