TWP/MWR/C2 - Uncertainty in clock time

At ARCS2, the MWR computer clock was not being updated because no NTP time service 
software was installed on the computer. During Nauru99, on 6/24/99, the clock was found to be 3 
minutes and 17 seconds fast. 

Assuming that the time was properly set at installation on 10/26/98 (which is not 
indicated in the installation report) and never reset until 6/24/99, the rate of time drift on 
the computer was about +0.8 seconds per day. However, if the time was not reset since 
integration at AIS on 1/14/98 (which is recorded in my integration notes), then the rate of 
drift is about +0.4 seconds per day.

The computer was replaced and time service started on 7/30/99.

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

TWP/MWR/C2 - Installation

The Nauru ARCS was installed during the period September-November
1998.  Data were being collected by the end of October, but for the
first several weeks of November, the site was undergoing considerable
change, so data from that period should be used with caution.  The
official site dedication occured on November 20.  Most on-site
activity ended following the dedication so we will consider November
20 to be the beginning of the Nauru operations.  The last members of
the installation team left Nauru on November 24.

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

TWP/MWR/C1 - Rain on window

The data is subject to contamination due to rain on the sensor window
and should be used with caution because the heater/blower assembly that
prevents water from accumulating on the sensor's teflon window was out
of commission.

• wet_window
• Water, liquid, total along line-of-sight path(liq)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Temperature, brightness, longwave(ir_temp)
• 23.8 GHz sky brightness temperature(tbsky23)
• Total water vapor along LOS path(vap)

TWP/MWR/C2 - Excessive wet_window flags

The wet_window flag is set high more than expected from the measured value of liquid water 
path. This may be caused by dew or, if the heater sensivity is slightly misadjusted, by 
the diurnal variation in ambient temperature.

The "wet_window" flag is an indicator of moisture on the MWR window which invalidates the 
measurements of precipitable water vapor and liquid water path. Sometimes this flag can 
be incorrectly set high or low if the heater sensivity is slightly misadjusted. The heater 
adjustment is a resistive device that is dependent on ambient temperature. Another 
indicator of moisture on the window is unreasonably high ( > 3*liquid_retrieval_rms_accuracy ) 
values of "liq".

• wet_window

TWP/MWR/C3 - Elevated Skybrightness Temperatures

For an unknown reason, the MWR began to exhibit elevated sky brightness 
temperatures. This problem was corrected when the instrument was power-cycled.

• Water, liquid, total along line-of-sight path(liq)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/MWR/C3 - Wet Window Flag not correct

The moisture sensor threshold voltage in the MWR configuration file was 
set to the wrong value for the new heater/blower assembly. This caused the 
wet window flag to not be set high during times of rain.

• wet_window

TWP/MWR/C3 - 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 SGP 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 version 4.12).

• bbn23
• Water, liquid, total along line-of-sight path(liq)
• bb23
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• bbn31
• bb31
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/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 SGP 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.

• Water, liquid, total along line-of-sight path(liq)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• 23.8 GHz sky brightness temperature(tbsky23)
• Total water vapor along LOS path(vap)

TWP/MWR/C3 - 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.

• tknd
• tkxc

TWP/MWR/C2 - thermal instability

The MWR required an unusually long time to reach thermal stability after a 4-day outage 
due to a power failure that damaged the blower/heater assembly. Also during this period, 
the heater, which had been replaced, appears to have been on continously, causing the data 
to be inappropriately flagged.

• tc31
• tnd_nom23
• sky31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• wet_window
• sky23
• tnd_nom31
• tc23
• Water, liquid, total along line-of-sight path(liq)
• Total water vapor along LOS path(vap)
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/MWR/C1 - wrong azimuth

The MWR was initially installed at an azimuth angle defined as 180 degrees but the value 
in the configuration file was not changed from the default of 0 degrees. In examining 
photos taken during the installation of the AWS tower, I noticed that the MWR was rotated 
opposite the normal orientation. The value in the configuration file was changed to reflect 
the actual azimuth of the instrument.

• actaz

TWP/MWR/C2 - Data collection problem

Large, frequent data gaps occurred due to a failing laptop computer. The problem was 
corrected when a new computer was installed.

• tnd_nom23
• tnd23
• Sky infrared temperature(sky_ir_temp)
• North latitude(lat)
• sky23
• Water, liquid, total along line-of-sight path(liq)
• East longitude(lon)
• bbn23
• time_offset
• bb31
• Temperature, brightness, longwave(ir_temp)
• actel
• tkbb
• wet_window
• tc23
• 23.8 GHz sky brightness temperature(tbsky23)
• sky31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• tnd_nom31
• tkair
• tkxc
• tknd
• Total water vapor along LOS path(vap)
• bb23
• tnd31
• bbn31
• Altitude above mean sea level(alt)
• tc31
• actaz
• base_time

TWP/MWR/C2 - Heater problem

When the wiring of the air temperature sensor was checked the heater apparently began 
activating too often.

• wet_window

TWP/MWR/C2 - mixer temperature

When the wiring of the air temperature sensor was checked the mixer temperature 
unexpectedly decreased 4 degrees. It increased to its normal value when the dielectric window was 
replaced. The problem was probably caused by a loose and/or corroded connection.

• tkxc

TWP/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 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).

The Rosenkranz-based retrieval coefficients became active at TWP.C2 20020427.0600.  The 
MONORTM-based retrieval coefficients became active at TWP.C2 20050630.2100.

Note: The TWP.C2 data for 19981028-20050630 have been reprocessed to apply the 
MONORTM-based retrievals for all time.  The reprocessed data were archived 20061003.

• Water, liquid, total along line-of-sight path(liq)
• Total water vapor along LOS path(vap)

TWP/MWR/C3 - 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 was active at TWP.C3 from
inception of the data, 20020227.0151.  The MONORTM-based retrieval
coefficients became active at TWP.C3 20050630.2100.

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.

• Water, liquid, total along line-of-sight path(liq)
• Total water vapor along LOS path(vap)

TWP/MWR/C1 - 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 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).

The Rosenkranz-based retrieval coefficients became active at TWP.C1 
20020504.0200.  The MONORTM-based retrieval coefficients became active 
at TWP.C1 20050630.2100.

Note: The TWP.C1 data for 19961011-20050630 have been reprocessed to apply the

• Water, liquid, total along line-of-sight path(liq)
• Total water vapor along LOS path(vap)

TWP/MWR/C1 - New software version (4.15) installed

A problem began with the installation of MWR.EXE version 4.12 in October 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 9/13/2005. As a consequence of this 
upgrade, the tip curve frequency increased. The tip cycle time decreased from ~60s to ~50s.

• tkair
• Sky infrared temperature(sky_ir_temp)
• bbn31
• bb31
• tnd_nom23
• bb23
• tnd_nom31
• sky23
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Water, liquid, total along line-of-sight path(liq)
• bbn23
• tc31
• tkxc
• Temperature, brightness, longwave(ir_temp)
• tnd31
• tnd23
• sky31
• tc23
• tkbb
• tknd
• 23.8 GHz sky brightness temperature(tbsky23)
• Total water vapor along LOS path(vap)

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

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

• tnd_nom23
• sky31
• tnd23
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Sky infrared temperature(sky_ir_temp)
• sky23
• tnd_nom31
• Water, liquid, total along line-of-sight path(liq)
• tkair
• tkxc
• bbn23
• bb31
• Total water vapor along LOS path(vap)
• tknd
• tnd31
• bb23
• bbn31
• Temperature, brightness, longwave(ir_temp)
• tc31
• tkbb
• tc23
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/MWR/C3 - New software version (4.15) installed

A problem began with the installation of MWR.EXE version 4.12 in October 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 9/20/2005. As a consequence of this 
upgrade, the tip curve frequency increased. The tip cycle time decreased from ~60s to ~50s.

• tknd
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• tnd_nom23
• tkbb
• tnd23
• sky31
• Sky infrared temperature(sky_ir_temp)
• tc31
• sky23
• tnd31
• tnd_nom31
• tc23
• bb23
• Water, liquid, total along line-of-sight path(liq)
• bbn23
• Total water vapor along LOS path(vap)
• bbn31
• bb31
• 23.8 GHz sky brightness temperature(tbsky23)
• tkair
• tkxc

TWP/MWR/C3 - Missing data

Data are missing and unrecoverable.

• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Altitude above mean sea level(alt)
• tkbb
• tnd23
• sky31
• Sky infrared temperature(sky_ir_temp)
• tc23
• tnd_nom31
• bb23
• East longitude(lon)
• bbn31
• time_offset
• tkxc
• wet_window
• tknd
• tnd_nom23
• North latitude(lat)
• tc31
• tnd31
• sky23
• base_time
• Water, liquid, total along line-of-sight path(liq)
• bbn23
• Total water vapor along LOS path(vap)
• bb31
• tkair
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/MWR/C3 - REPROCESS- Updated retrieval coefficients

The statistical retrieval coefficients currently in use at the Darwin (TWP/C3) site were 
developed using radiosonde RS80 launched from Manus Island during the TOGA-COARE 
experiment.
Data from Manus Island have minimal seasonality, therefore a single, annual set of 
coefficients was used at all three sites. Retrievals using these coefficients are sufficiently 
accurate especially during the local summer months (December-January). However, the Darwin 
site displays a summer/winter seasonality resulting in larger differences during the 
southern winter (May-
June).
Since we now have enough radiosonde soundings (RS80 and RS90) available at the Darwin 
site, the Darwin coefficients were modified to better reflect the local seasonality.

• Water, liquid, total along line-of-sight path(liq)
• Total water vapor along LOS path(vap)

TWP/MWR/C2 - software upgrade (version 3.29)

The MWR operating program was upgraded to version 3.29 on 30 July 1999. This version 
included a beam width correction as well as provided the capability to automatically level the 
elevation mirror (that is, to automatically detect and correct offsets in the elevation 
angle stepper motor position.)
   
The improvement in the quality of the tip curves resulting from the auto-leveling has been 
dramatic: differences in the brightness temperatures at 3 airmasses (19.5 and 160.5 
degrees) have been reduced from +/- 5 K to +/- 0.5 K. In order to take full advantage of this 
improvement to detect and reject cloudy tip curves, the minimum value of the 
goodness-of-fit coefficient for a valid tip curve has been increased from 0.995 to 0.998.

The data prior to July 30 1999 do not include beam-width and mirror-leveling corrections.

• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Water, liquid, total along line-of-sight path(liq)
• Total water vapor along LOS path(vap)
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/MWR/C1 - Software Change

The MWR operating software was changed on 27 February 1999 to provide additional
functionality as described below.
   
NEW FEATURES
1. Faster sampling rate
   
Standard line-of-sight (LOS) observations can now be acquired at 15-second intervals vs. 
20-second intervals previously. (The standard LOS cycle is comprised of one sky sample per 
blackbody sample and gain update.)
   
2. More flexible sampling strategy
   
Multiple sky observations can be acquired during a LOS cycle, up to 1024 per gain update. 
This permits sky samples to be acquired at intervals of 2.67 seconds for improved 
temporal resolution of cloud liquid water variations and better coordination with the millimeter 
cloud radar during IOPs.
   
3. Separation of zenith LOS observations from TIP data
   
When the radiometer is in TIP mode, the zenith LOS observations are now extracted, the PWV 
and LWP computed and reported separately in the output file. This eliminates the periods 
of missing LOS data during calibration checks/updates.
   
4. Automatic self-calibration
   
The software now permits the calibration to be updated at specified intervals or 
continuously. In the first case, LOS mode is automatically changed to TIP mode at user-specified 
intervals or whenever clear sky conditions occur, the tip data reduced, the calibration 
updated, and the radiometer returned to LOS mode without operator intervention. In the 
second case, the radiometer is continuously is TIP mode until changed by the operator.
   
5. Graphical user display
   
The graphical display is comprised of a status display, a message display, a temperature 
plot, a plot of the retrieved PWV and LWP, and (in TIP mode) a plot of the latest tip 
curves.

• tkair
• actel
• Sky infrared temperature(sky_ir_temp)
• East longitude(lon)
• actaz
• bb31
• tnd_nom23
• sky23
• bbn23
• tkxc
• Temperature, brightness, longwave(ir_temp)
• tnd31
• sky31
• tc23
• tkbb
• time_offset
• 23.8 GHz sky brightness temperature(tbsky23)
• wet_window
• bbn31
• bb23
• tnd_nom31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Water, liquid, total along line-of-sight path(liq)
• tc31
• tnd23
• North latitude(lat)
• tknd
• base_time
• Altitude above mean sea level(alt)
• Total water vapor along LOS path(vap)

TWP/MWR/C1 - software upgrade (version 3.29)

The MWR operating program was upgraded to version 3.29 on 15 March 1999. This version 
included a beam width correction as well as provided the capability to automatically level 
the elevation mirror (that is, to automatically detect and correct offsets in the elevation 
angle stepper motor position.)
   
The improvement in the quality of the tip curves resulting from the auto-leveling has been 
dramatic: differences in the brightness temperatures at 3 airmasses (19.5 and 160.5 
degrees) have been reduced from +/- 5 K to +/- 0.5 K. In order to take full advantage of this 
improvement to detect and reject cloudy tip curves, the minimum value of the 
goodness-of-fit coefficient for a valid tip curve has been increased from 0.995 to 0.998.

• Water, liquid, total along line-of-sight path(liq)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• 23.8 GHz sky brightness temperature(tbsky23)
• Total water vapor along LOS path(vap)

TWP/MWR/C2 - Missing data

The heater blower assembly was causing the fuse to blow.  The instrument was taken offline 
until a replacement arrives.

• tnd_nom23
• tnd23
• Sky infrared temperature(sky_ir_temp)
• North latitude(lat)
• sky23
• Water, liquid, total along line-of-sight path(liq)
• East longitude(lon)
• bbn23
• time_offset
• bb31
• Temperature, brightness, longwave(ir_temp)
• actel
• tkbb
• wet_window
• tc23
• 23.8 GHz sky brightness temperature(tbsky23)
• sky31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• tnd_nom31
• tkair
• tkxc
• tknd
• Total water vapor along LOS path(vap)
• bb23
• tnd31
• bbn31
• Altitude above mean sea level(alt)
• tc31
• actaz
• base_time

TWP/MWR/C1 - Radiometer failure

The instrument stopped responding and had to be powered off. Suspect cause of failure is a 
faulty digital board.

• tkair
• actel
• Sky infrared temperature(sky_ir_temp)
• East longitude(lon)
• actaz
• bb31
• tnd_nom23
• sky23
• bbn23
• tkxc
• Temperature, brightness, longwave(ir_temp)
• tnd31
• sky31
• tc23
• tkbb
• time_offset
• 23.8 GHz sky brightness temperature(tbsky23)
• wet_window
• bbn31
• bb23
• tnd_nom31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Water, liquid, total along line-of-sight path(liq)
• tc31
• tnd23
• North latitude(lat)
• tknd
• base_time
• Altitude above mean sea level(alt)
• Total water vapor along LOS path(vap)

TWP/MWR/C3 - Sun in field of view of radiometer

Each day around local noon there is an increase in the brightness temperature due to the 
sun being in the field of view of the radiometer.

• Water, liquid, total along line-of-sight path(liq)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Total water vapor along LOS path(vap)
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/MWR/C2 - Missing Data

Data are missing and unrecoverable.

• tnd_nom23
• tnd23
• Sky infrared temperature(sky_ir_temp)
• North latitude(lat)
• sky23
• Water, liquid, total along line-of-sight path(liq)
• East longitude(lon)
• bbn23
• time_offset
• bb31
• Temperature, brightness, longwave(ir_temp)
• actel
• tkbb
• wet_window
• tc23
• 23.8 GHz sky brightness temperature(tbsky23)
• sky31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• tnd_nom31
• tkair
• tkxc
• tknd
• Total water vapor along LOS path(vap)
• bb23
• tnd31
• bbn31
• Altitude above mean sea level(alt)
• tc31
• actaz
• base_time

TWP/MWR/C2 - Reprocessed: New Calibration coefficients

On 11/27 a spare radiometer was installed to replace a faulty radiometer. Once the 
radiometer started to collect data it used the default calibration coefficients until it 
collected enough tip data to determine its own coefficients.

The data were reprocessed to apply corrected calibrations and the reprocessed data were 
archived 20061222.

• tc31
• tnd_nom23
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• tnd23
• tnd_nom31
• tc23
• Water, liquid, total along line-of-sight path(liq)
• Total water vapor along LOS path(vap)
• tnd31
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/MWR/C1 - Missing data

Data are missing and unrecoverable.

• tkair
• actel
• Sky infrared temperature(sky_ir_temp)
• East longitude(lon)
• actaz
• bb31
• tnd_nom23
• sky23
• bbn23
• tkxc
• Temperature, brightness, longwave(ir_temp)
• tnd31
• sky31
• tc23
• tkbb
• time_offset
• 23.8 GHz sky brightness temperature(tbsky23)
• wet_window
• bbn31
• bb23
• tnd_nom31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Water, liquid, total along line-of-sight path(liq)
• tc31
• tnd23
• North latitude(lat)
• tknd
• base_time
• Altitude above mean sea level(alt)
• Total water vapor along LOS path(vap)

TWP/MWR/C1/C2 - Sun in the field of view

Every day between around noon local time (usually between 1 and 2 AM UTC time) there is an 
increase in the brightness temperatures due to the sun in the field of view of the 
radiometer.

The effect lasts less than an hour around local noon (usually between 1 and 2 AM UTC 
time).  The effect appears as a smooth increase and decrease in brightness temperature.

• sky31
• sky23
• Water, liquid, total along line-of-sight path(liq)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• 23.8 GHz sky brightness temperature(tbsky23)
• Total water vapor along LOS path(vap)

• sky31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• sky23
• Water, liquid, total along line-of-sight path(liq)
• Total water vapor along LOS path(vap)
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/MWR/C1 - Intermittent data

After a computer change the MWR program did not restart properly.  Data are intermittent 
between 6/12 and 6/17.

• tkair
• actel
• Sky infrared temperature(sky_ir_temp)
• East longitude(lon)
• actaz
• bb31
• tnd_nom23
• sky23
• bbn23
• tkxc
• Temperature, brightness, longwave(ir_temp)
• tnd31
• sky31
• tc23
• tkbb
• time_offset
• 23.8 GHz sky brightness temperature(tbsky23)
• wet_window
• bbn31
• bb23
• tnd_nom31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Water, liquid, total along line-of-sight path(liq)
• tc31
• tnd23
• North latitude(lat)
• tknd
• base_time
• Altitude above mean sea level(alt)
• Total water vapor along LOS path(vap)

TWP/MWR/C1 - Incorrect ambient temperature readings

Starting on 11/21 the ambient temperature readings are intermittent and have spikes.
Site operators replaced the dew-blower on 12/11 and readings came back to normal

• tkair

TWP/MWR/C1 - Short periods of wrong ambient temperature

During this month there are a few intermittent instances of bad ambient temperature 
readings. I will summarize here these short time ranges:
20080909 between 02:00 and 03:00 UTC
20080909 between 09:00 and 14:00 UTC

Additionally the ambient temperature has short but frequent data gaps.  The data gaps are 
very short (less than one hour). Users could interpolate missing data or use alternative 
sensors such as the surface meteorological data available for the site.

• tkair

TWP/MWR/C2 - Incorrect ambient temperature during rain

The ambient temperature was approximately 15 degree higher than what it should be when it 
was raining and the heater came. On Jan 9 2009 the dewblower was replaced which solved 
the problem.

The increased ambient temperature (tkair) was happening during times of rain and users 
should always disregard MWR data during rain events.  Therefore this DQR is colored 
transparent.

• tkair

TWP/MWR/C1 - Ambient temperature data missing

The ambient temperature readings (tkair) suddenly failed. The sensor was replaced on Feb 
6.

• tkair

TWP/MWR/C2 - Intermittent data

There are several short data gaps (usually 2 to 7 hours) in the data due to computer 
malfunction. The problem was solved by replacing the computer.

• tnd_nom23
• tnd23
• Sky infrared temperature(sky_ir_temp)
• North latitude(lat)
• sky23
• Water, liquid, total along line-of-sight path(liq)
• East longitude(lon)
• bbn23
• time_offset
• bb31
• Temperature, brightness, longwave(ir_temp)
• actel
• tkbb
• wet_window
• tc23
• 23.8 GHz sky brightness temperature(tbsky23)
• sky31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• tnd_nom31
• tkair
• tkxc
• tknd
• Total water vapor along LOS path(vap)
• bb23
• tnd31
• bbn31
• Altitude above mean sea level(alt)
• tc31
• actaz
• base_time

TWP/MWR/C1 - Intermittent data due to computer problems

Between 1/7 and 1/9 there are large segments of data missing because of a computer 
problem.

• tkair
• actel
• Sky infrared temperature(sky_ir_temp)
• East longitude(lon)
• actaz
• bb31
• tnd_nom23
• sky23
• bbn23
• tkxc
• Temperature, brightness, longwave(ir_temp)
• tnd31
• sky31
• tc23
• tkbb
• time_offset
• 23.8 GHz sky brightness temperature(tbsky23)
• wet_window
• bbn31
• bb23
• tnd_nom31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Water, liquid, total along line-of-sight path(liq)
• tc31
• tnd23
• North latitude(lat)
• tknd
• base_time
• Altitude above mean sea level(alt)
• Total water vapor along LOS path(vap)

TWP/MWR/C2 - Missing ambient temperature

The tkair readings (ambient temperatures) is very intermittent and mostly missing for the 
month of May and June. On June 14 the dewblower was replaced.

• tkair

TWP/MWR/C1 - Rain events not flagged

On some occasions the rain flag did not flag data during likely rain events.

Users should carefully examine the data to ensure that they are not contaminated by rain. 
Also examine the brightness temperature qc variables.

• Water, liquid, total along line-of-sight path(liq)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• 23.8 GHz sky brightness temperature(tbsky23)
• Total water vapor along LOS path(vap)

TWP/MWR/C2 - Temperature sensor failure

The temperature sensor was malfunctioning between 3/3 and 4/17.

• tkair

TWP/MWR/C1 - Erratic surface temperature readings

The surface temperature readings were erratic at times between 5/14 and 6/21.

• tkair

TWP/MWR/C1 - Spikes in temperature sensor readings

The air temperature readings had occasional spikes. The temperature sensor was replaced on 
8/21.

• tkair

TWP/MWR/C2 - Ambient temp sensor failure

The temperature sensor was malfunctioning. It was replaced on 5/31/2013.

• tkair

TWP/MWR/C2 - Deteriorating data quality

The data quality for this instrument noticeably deteriorated starting in June 2013, though 
the start date of this DQR is an estimated start of the problem. 

The tip curve data were degraded and the elevation readings showed large differences on 
the two sides of the scan. The quality of the resulting zenith brightness temperatures were 
degraded and the resulting LWP and PWV were incorrect.

• sky31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• sky23
• Water, liquid, total along line-of-sight path(liq)
• Total water vapor along LOS path(vap)
• 23.8 GHz sky brightness temperature(tbsky23)

TWP/MWR/C1 - Intermittent data

Data are intermittent during this time. Users should avoid using these data

• tkair
• actel
• Sky infrared temperature(sky_ir_temp)
• East longitude(lon)
• actaz
• bb31
• tnd_nom23
• sky23
• bbn23
• tkxc
• Temperature, brightness, longwave(ir_temp)
• tnd31
• sky31
• tc23
• tkbb
• time_offset
• 23.8 GHz sky brightness temperature(tbsky23)
• wet_window
• bbn31
• bb23
• tnd_nom31
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Water, liquid, total along line-of-sight path(liq)
• tc31
• tnd23
• North latitude(lat)
• tknd
• base_time
• Altitude above mean sea level(alt)
• Total water vapor along LOS path(vap)

TWP/MWR/C1 - Instrument malfunction

The instrument had a malfunction of the 31 GHz channel and was shutdown. Users should not 
use the data during this time.

• sky31
• bbn31
• bb31
• tnd_nom31
• Water, liquid, total along line-of-sight path(liq)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• tc31
• Total water vapor along LOS path(vap)
• tnd31

TWP/MWR/C3 - Occasional incorrect surface temperature

The surface temperature has occasional incorrect reading.

• tkair

TWP/MWR/C2 - Software Change

The MWR operating software was changed on 19 November 1998 to provide additional 
functionality as described below.
   
NEW FEATURES
1. Faster sampling rate
   
Standard line-of-sight (LOS) observations can now be acquired at 15-second intervals vs. 
20-second intervals previously. (The standard LOS cycle is comprised of one sky sample per 
blackbody sample and gain update.)
   
2. More flexible sampling strategy
   
Multiple sky observations can be acquired during a LOS cycle, up to 1024 per gain update. 
This permits sky samples to be acquired at intervals of 2.67 seconds for improved 
temporal resolution of cloud liquid water variations and better coordination with the millimeter 
cloud radar during IOPs.
   
3. Separation of zenith LOS observations from TIP data
   
When the radiometer is in TIP mode, the zenith LOS observations are now extracted, the PWV 
and LWP computed and reported separately in the output file. This eliminates the periods 
of missing LOS data during calibration checks/updates.
   
4. Automatic self-calibration
   
The software now permits the calibration to be updated at specified intervals or 
continuously. In the first case, LOS mode is automatically changed to TIP mode at user-specified 
intervals or whenever clear sky conditions occur, the tip data reduced, the calibration 
updated, and the radiometer returned to LOS mode without operator intervention. In the 
second case, the radiometer is continuously is TIP mode until changed by the operator.
   
5. Graphical user display
   
The graphical display is comprised of a status display, a message display, a temperature 
plot, a plot of the retrieved PWV and LWP, and (in TIP mode) a plot of the latest tip 
curves.

• tnd23
• tkair
• tknd
• tnd31