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 - poor air temperature values

After the air temperature sensor was rewired due to a change with the new blower 
(D030515.3), the measurement was initially incorrect. There is no apparent cause for the bad 
signal or its improvement.

• tkair

• tkair

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 - Possible loss of accuracy due to missing blower

On 7/09 the MWR blower failed. The blower prevents snow and liquid drop from accumulating 
on the window. Accumulation of snow or liquid results in a loss of accuracy of the 
instrument. The loss of accuracy has consequencies on the retrieved liquid water path and 
precipitable water vapor. Usually there will be an overestimation of liquid and vapor. The 
blower was repaired and reinstalled on 7/20. Between 7/9 and 7/20 the tkair variable is 
unavailable as well.

• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• 23.8 GHz sky brightness temperature(tbsky23)
• sky31
• sky23
• Total water vapor along LOS path(vap)
• wet_window
• tkair

• vaptip
• tipsky31
• tipsky23
• liqtip
• wet_window
• tbskytip31
• tkair
• tbskytip23

NSA/MWR/C1 - Instrument problem, Heater problem

The heater of the MWR was ON all the time even when the moisture sensor was dry. Jim 
Liljegren suspected a problem with the relay that activates the heater. The suggested action 
was to send the faulty assembly to SGP for repair and get a spare unit from SGP.
The spare unit was sent on 9/15 and was installed on 10/18.

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

• Raw data stream - documentation not supported

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
• Temperature, Sky Infra-Red(sky_ir_temp)
• sky23
• tkxc
• Total water vapor along LOS path(vap)
• tkbb
• bbn23
• tkair
• Total liquid water along LOS path(liq)
• 23.8 GHz sky brightness temperature(tbsky23)
• tnd31
• bb23
• tc23
• sky31
• tnd_nom31
• tc31
• Temperature, brightness, longwave(ir_temp)
• bbn31

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

NSA/MWR/C1 - Reprocess: wrong calibration

When MWR#20 was returned to service on 9/1/2005, the calibration had changed as a result 
of the repairs made by Radiometrics and the RF deck temperature had been set to 325K for 
testing. On 9/2, the temperature was decreased to 307K to prevent thermal instability in 
winter and the calibration was changed in the configuration file with the values supplied 
on the repair report.  

The data need to be reprocessed with the calibration coefficients that were automatically 
derived after these changes were put into affect. They are: tnd_nom23=185.621, 
tnd_nom31=158.801, tc23=-0.022, tc31=-0.039.

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

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

• vaptip
• liqtip
• tbskytip31
• tbskytip23

NSA/MWR/C1 -  Incorrect time stamp

On Sept 27 the motherboard of the MWR computer was replaced. Following the replacement, 
the date on the computer was not set to the correct time of day, therefore the date and 
time in the files were wrong. The time on the computer was reset on Sept. 30. Time stamps 
between Sept. 27 and Sept. 30 were later corrected based on gathered information, however 
they may have as much as 5 minutes of uncertainty.

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

• Raw data stream - documentation not supported

NSA/MWR/C1 - TKAIR sensor failure

Between 7/14 and 7/28 the tkair variable is missing most of the time and sometimes has 
large negative spikes.  On 7/28, the sensor was cleaned of corrosion and the readings came 
back to normal.

• tkair

NSA/MWR/C1 - Rain sensor always on

The rain sensor was always on between 10/5 and 10/23 2006.
The user should be aware that not all data flagged as rainy are actually rainy. The 
problem was caused by a shift in the sensitivity of the rain sensor and was corrected by 
changing the sensor threshold in the configuration file.

• wet_window

• wet_window

NSA/MWR/C1 - Spikes in air temperature readings

During this month there are occasional negative spikes in the Tkair variable. The problem 
may be corrosion in the temperature sensor or the infiltration of water from melting snow.
The dewblower was replaced and a new sensor installed

• tkair

• tkair

NSA/MWR/C1 - Missing surface air temperature data

Some wires in the dewblower were not correctly configured.

• tkair

• tkair

NSA/MWR/C1 - Incorrect brightness temperatures and retrievals

The brightness temperatures and retrieved PWV and LWP show a sudden jump and have values 
that are too high. The suddenly jump back to normal at around 1800 UTC. All other 
parameters seem reasonable so the cause of the jump may just be due to accumulation of either 
snow or melting ice on the radome.

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

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

• vaptip
• liqtip
• tbskytip31
• tkair
• tbskytip23

NSA/MWR/C1 - RFI screening test

The instrument was covered with a shield to test the effect on the RF interference that is 
affecting the measurements since February. The test was performed on 4/15 and 4/16 for a 
few hours.

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

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

NSA/MWR/C1 - High noise in 23.8-GHz channel

Starting approximately on February 13 the MWR experienced high level of noise in the 23.8 
GHz channel. The spikes became more prominent around Feb 17 and increased after that date 
as well. The cause of the interference was identified as the nearby MWRP on Oct 13 and 
the instruments were realigned.

• sky23
• Total water vapor along LOS path(vap)
• 23.8 GHz sky brightness temperature(tbsky23)

• vaptip
• tipsky23
• tbskytip23

NSA/MWR/C1 - Intermittent air temperature readings

Starting on 5/23 the air temperature readings (tkair) were intermittent and had negative 
spikes

• tkair

• tkair

NSA/MWR/C1 - Air temperature readings missing

The air temperature readings (tkair) dropped on 5/26. The signal was restored on 6/10.

• tkair

• tkair

NSA/MWR/C1 - Elevated noise

The data have high noise levels.

• 31.4 GHz sky brightness temperature(tbsky31)
• sky23
• Total water vapor along LOS path(vap)
• 23.8 GHz sky brightness temperature(tbsky23)
• sky31

• vaptip
• tipsky23
• tipsky31
• tbskytip31
• tbskytip23

NSA/MWR/C1 - Missing data

Data are missing and unrecoverable.

• 31.4 GHz sky brightness temperature(tbsky31)
• Temperature, Sky Infra-Red(sky_ir_temp)
• sky23
• tkxc
• Total water vapor along LOS path(vap)
• alt
• tkbb
• bbn23
• base_time
• tkair
• 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)
• 23.8 GHz sky brightness temperature(tbsky23)
• tnd31
• tc23
• actel
• tc31
• actaz

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