NSA/C2/VCEIL - Occasional Data Transmission Problems

A combination of problems lead to occasional short period loss (usually lesss than 2 
minutes) of data for ceilometer during this period.

• Time offset of tweaks from base_time(time_offset)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Dummy altitude for Zeb(alt)
• Flag indicating aeri retrieval status(status_flag)
• Vertical visibility(vertical_visibility)
• lat(lat)
• Detection status. See details(detection_status)
• Second lowest cloud base height(second_cbh)
• Millivolts at internal ADC input(window_contamination)
• Backscatter sum(sum_backscatter)
• Lowest cloud base height detected.(first_cbh)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Altitude of highest signal(alt_highest_signal)
• base time(base_time)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Third cloud base height(third_cbh)
• Laser temperature(laser_temperature)
• Warning and alarm status bits(status_string)
• Degrees from vertical (0 to +90)(tilt_angle)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• lon(lon)
• range(range)

• Laser temperature(laser_temperature)
• Dummy altitude for Zeb(alt)
• lon(lon)
• Degrees from vertical (0 to +90)(tilt_angle)
• Altitude of highest signal(alt_highest_signal)
• Second lowest cloud base height(second_cbh)
• lat(lat)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Flag indicating aeri retrieval status(status_flag)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Backscatter sum(sum_backscatter)
• Lowest cloud base height detected.(first_cbh)
• base time(base_time)
• Time offset of tweaks from base_time(time_offset)
• range(range)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Vertical visibility(vertical_visibility)
• Detection status. See details(detection_status)
• Warning and alarm status bits(status_string)
• Millivolts at internal ADC input(window_contamination)
• Third cloud base height(third_cbh)

• Raw data stream - documentation not supported(Raw data stream - documentation not supported)

NSA/ISSSONDE/C1 - Reprocess: Pressure variable name unstable

During the time period referenced, the variable for pressure should have been recorded as 
"pres", but instead was recorded as "press" for the first 8 months and then was unstable 
for the next 2 months with some headers reporting pressure as "pres" and others reporting 
pressure as "press".  From 1/14/02 onward the variable name is consistently "pres".

Data quality are not affected, but the variability may prove challenging for users.  A 
reprocessing request has been submitted.

• Retrieved pressure profile(pres)

• Retrieved pressure profile(pres)

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/SONDE/C1 - Incorrect surface altitude

The value of the station altitude (relative to mean sea level) is
incorrect in all NSA radiosonde files prior to 2/14/2004.  The correct
value is 8 m.  The incorrect value can be different.  Prior to 4/24/2002
(in platform nsaisssonde...) it was given as 12 m.  From 4/24/2002 to
2/13/2004 (in platform nsasondewnpn...) it is almost always given as
27 m (sometimes [rarely] 17 m).

• Dummy altitude for Zeb(alt)

• Raw data stream - documentation not supported(Raw data stream - documentation not supported)

• Dummy altitude for Zeb(alt)

• Raw data stream - documentation not supported(Raw data stream - documentation not supported)

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)