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.

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

• 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)

TWP/MET/C3 - WIND DIRECTION SENSOR #2 MISALIGNED

Wind direction sensor #2 was misaligned and off by 15 degrees.

• Wind #2 direction vector average(wind2_dir_vec_avg)
• Wind #2 direction standard deviation(wind2_dir_sd)

• Wind #2 direction standard deviation(wind2_dir_sd)
• Wind #2 direction vector average(wind2_dir_vec_avg)

TWP/SMET/C3 - Intermittent Pressure Sensor Failure

The Barometric Pressure sensor was intermittently failing at TWP site C3 Darwin.  At times 
there were large pressure fluctuations occurring on the order of 24 mb in a few minutes. 
 Times of large pressure fluctuations are readily apparent in the data.  At these times 
the data should be carefully analyzed before determining it's usefulness.  In between the 
periods of large fluctuations the readings appear to be stable.  It is still suggested 
that independent pressure data be obtained for comparison before use.

• Barometric Pressure(atmos_pressure)

• Barometric Pressure(atmos_pressure)

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

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.

• Mixer kinetic (physical) temperature(tkxc)
• (tknd)

TWP/SMET/C3 - Data reported at 15sec rather than 60s intervals

Data in these data streams should be reports at 60sec intervals, but
the logger program running during this time had the interval set to
15s.  Users will have to average the 15sec data to get 60sec data.

• Vapor pressure mean(vappress_mean)
• External voltage(external_voltage)
• Temperature minimum(temp_min)
• Precipitation standard deviation(precip_sd)
• base time(base_time)
• Precipitation mean(precip_mean)
• Barometric Pressure(atmos_pressure)
• Wind #1 direction vector average(wind1_dir_vec_avg)
• Wind #2 speed maximum(wind2_spd_max)
• Wind #2 speed standard deviation(wind2_spd_sd)
• Wind #1 speed minimum(wind1_spd_min)
• lat(lat)
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• Dummy altitude for Zeb(alt)
• Logger panel temperature(logger_temp)
• Std Dev of Air Temperature(temp_sd)
• Vapor pressure standard deviation(vappress_sd)
• Relative humidity maximum(relh_max)
• Mean Air Temperature or Hardware Error(temp_mean)
• lon(lon)
• Wind #1 speed maximum gust(wind1_spd_max_gust)
• Std Dev of Relative Humidity or Hardware Error Code(relh_sd)
• Mean Relative Humidity(relh_mean)
• Time offset of tweaks from base_time(time_offset)
• Relative humidity minimum(relh_min)
• Wind #2 direction standard deviation(wind2_dir_sd)
• Bit data. See details.(bit_data)
• Wind #2 direction vector average(wind2_dir_vec_avg)
• Wind #1 speed standard deviation(wind1_spd_sd)
• Wind #2 speed minimum(wind2_spd_min)
• Battery Voltage(internal_voltage)
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Temperature maximum(temp_max)
• precipitation minimum(precip_min)
• Wind #2 speed arithmetic average(wind2_spd_arith_avg)
• Wind #2 speed vector average(wind2_spd_vec_avg)
• Wind #1 speed maximum(wind1_spd_max)
• Precipitation maximum(precip_max)
• Wind #1 direction standard deviation(wind1_dir_sd)
• Wind #2 speed maximum gust(wind2_spd_max_gust)

• Time offset of tweaks from base_time(time_offset)
• Precipitation maximum(precip_max)
• Battery Voltage(internal_voltage)
• Wind #1 speed minimum(wind1_spd_min)
• Wind #2 speed maximum(wind2_spd_max)
• Wind #1 direction standard deviation(wind1_dir_sd)
• Wind #2 speed minimum(wind2_spd_min)
• Wind #1 speed maximum(wind1_spd_max)
• Mean Air Temperature or Hardware Error(temp_mean)
• Temperature maximum(temp_max)
• Barometric Pressure(atmos_pressure)
• Relative humidity maximum(relh_max)
• Mean Relative Humidity(relh_mean)
• Wind #1 direction vector average(wind1_dir_vec_avg)
• Wind #1 speed standard deviation(wind1_spd_sd)
• Std Dev of Relative Humidity or Hardware Error Code(relh_sd)
• Relative humidity minimum(relh_min)
• Bit data. See details.(bit_data)
• Temperature minimum(temp_min)
• Dummy altitude for Zeb(alt)
• Wind #2 speed maximum gust(wind2_spd_max_gust)
• Precipitation standard deviation(precip_sd)
• Wind #1 speed maximum gust(wind1_spd_max_gust)
• lon(lon)
• Wind #2 direction standard deviation(wind2_dir_sd)
• Wind #2 speed standard deviation(wind2_spd_sd)
• External voltage(external_voltage)
• lat(lat)
• Wind #2 speed arithmetic average(wind2_spd_arith_avg)
• Logger panel temperature(logger_temp)
• precipitation minimum(precip_min)
• Vapor pressure mean(vappress_mean)
• Vapor pressure standard deviation(vappress_sd)
• Wind #1 speed vector average(wind1_spd_vec_avg)
• Wind #2 direction vector average(wind2_dir_vec_avg)
• Precipitation mean(precip_mean)
• Wind #2 speed vector average(wind2_spd_vec_avg)
• base time(base_time)
• Wind #1 speed arithmetic average(wind1_spd_arith_avg)
• Std Dev of Air Temperature(temp_sd)

TWP/SMET/C3 - Negative rainfall rates

Due to limitations of the Zeno dataloggers all voltage measurements
from the optical rain gauge (ORG) were converted to rainfall rates. 
This resulted in negative values for rain rates.  Any value below
0.10 mm/hr should be considered to be 0 mm/hr.  New dataloggers 
alleviated this problem.

• Precipitation mean(precip_mean)
• Precipitation maximum(precip_max)
• Precipitation standard deviation(precip_sd)
• precipitation minimum(precip_min)

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.

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

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

• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)
• Total liquid water along zenith path using tip-derived brightness temperatures(liqtip)

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.

• Sky brightness temperature at 31.4 GHz(tbsky31)
• 23.8 GHz blackbody+noise injection signal(bbn23)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• 31.4 GHz blac2body+noise injection signal(bbn31)
• Temperature correction coefficient at 23.8 GHz(tc23)
• 23.8 GHz Blackbody signal(bb23)
• MWR column precipitable water vapor(vap)
• Averaged total liquid water along LOS path(liq)
• 31.4 GHz blackbody(bb31)
• 31.4 GHz sky signal(sky31)
• 23.8 GHz sky signal(sky23)
• Sky brightness temperature at 23.8 GHz(tbsky23)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• Temperature correction coefficient at 31.4 GHz(tc31)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• Sky Infra-Red Temperature(sky_ir_temp)
• Blackbody kinetic temperature(tkbb)
• Mixer kinetic (physical) temperature(tkxc)
• (tknd)
• Ambient temperature(tkair)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)

• Ambient temperature(tkair)
• Blackbody kinetic temperature(tkbb)
• (tknd)
• Temperature correction coefficient at 31.4 GHz(tc31)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• 23.8 GHz sky brightness temperature derived from tip curve(tbskytip23)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)
• Noise injection temp at 31.4 GHz derived from this tip(tnd31I)
• Temperature correction coefficient at 23.8 GHz(tc23)
• 23.8 GHz sky signal(tipsky23)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• 31.4 GHz blackbody(bb31)
• 31.4 GHz goodness-of-fit coefficient(r31)
• 31.8 GHz sky brightness temperature derived from tip curve(tbskytip31)
• 23.8 GHz blackbody+noise injection signal(bbn23)
• Total liquid water along zenith path using tip-derived brightness temperatures(liqtip)
• Mixer kinetic (physical) temperature(tkxc)
• 31.4 GHz blac2body+noise injection signal(bbn31)
• Noise injection temp at 23.8 GHz derived from this tip(tnd23I)
• 31.4 GHz sky signal(tipsky31)
• 23.8 GHz goodness-of-fit coefficient(r23)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• 23.8 GHz Blackbody signal(bb23)

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.

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

• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)
• Total liquid water along zenith path using tip-derived brightness temperatures(liqtip)

TWP/SMET/C3 - Reprocess: Barometric Data Changed from hPa to kPa

Barometric pressure data was converted from hPa to kPa in order to standardize the 
measurement units among ARM sites and to conform to accepted standard units determined by the 
scientific community.

• Barometric Pressure(atmos_pressure)

TWP/SMET/C3 - Reprocess: Tipping bucket rain gauge added

A tipping bucket rain gauge was added to the SMET suite of instruments effective 20060926. 
 Two new variables (count and rain amount) were added at the end of the twpsmet60sC1.b1 
datastream.  When reprocessing of this datastream occurs these variables will be added 
with -9999 (missing) as the value for dates prior to gauge installation.

• base time(base_time)