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.

• tbsky31_sdev
• tbsky23_sdev
• Total liquid water along LOS path(liq)
• ir_temp_sdev
• num_obs_irt
• liq_sdev
• num_obs
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• Temperature, brightness, longwave(ir_temp)
• Total water vapor along LOS path(vap)
• water_flag_fraction
• vap_sdev
• 31.4 GHz sky brightness temperature(tbsky31)

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

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• wet_window
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• Temperature, brightness, longwave(ir_temp)

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.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• tkxc
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

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.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• tkxc
• Total water vapor along LOS path(vap)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

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.

• 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)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

NSA/MWR/C1 - incorrect flagging of data

The wet window flag is set high more than expected.

• wet_window

• wet_window

• wet_window

NSA/MWR/C1 - incorrect flagging of data

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

• wet_window

• wet_window

• wet_window

NSA/MWR/C1 - Reprocess: calibration change

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

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

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• Total water vapor along LOS path(vap)

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

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.

• 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)

• 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)

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.

• 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)

• 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)

NSA/MWR/C1 - MWR digital board failure

A power failure at the site apparently damaged some of the components of the digital 
board. The MWR was replaced with a spare unit and returned to the manufacturer for repair.

• 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)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

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.

• 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)

• 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• Total liquid water along LOS path(liq)
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)

NSA/MWR/C1  - 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 changing the wiring and modifying the MWR software to read 
the signal from the appropriate corresponding channel.

• tkair

• Raw data stream - documentation not supported

• tkair

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.

• tkxc
• tknd

NSA/MWR/C1 - Reprocess: Revised Calibration 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.C1 
20020425.1900.  The MONORTM-based retrieval coefficients became active 
at NSA.C1 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.

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

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

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

• mean_liq_mwr
• mean_vap_mwr

• vaptip
• liqtip

NSA/MWR/C1 - 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.

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

• tnd23
• tkxc
• tnd_nom23
• bb31
• tc31
• tnd31I
• tkbb
• liqtip
• bbn31
• tbskytip31
• r31
• tkair
• vaptip
• bb23
• tnd_nom31
• tnd23I
• tknd
• tipsky31
• tc23
• tipsky23
• r23
• tbskytip23
• bbn23
• tnd31

NSA/MWR/C1 - Missing data

Data are missing and unrecoverable.

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

• lat
• tnd_nom23
• bb31
• tnd31I
• liqtip
• wet_window
• bbn31
• r31
• tkair
• tnd_nom31
• tknd
• lon
• tc23
• r23
• bbn23
• tnd23
• tkxc
• tc31
• actel
• tkbb
• alt
• tbskytip31
• actaz
• vaptip
• bb23
• tnd23I
• tipsky31
• time_offset
• tipsky23
• base_time
• tbskytip23
• tnd31