SGP/MWR/C1 - calibration checks

The MWR calibration was checked by a cryogenic (liquid nitrogen) 
blackbody target or (in the case of the Sept 2001 time period)
by pointing the mirror at an internal blackbody target.  The 
brightness temperatures and vap and liq retrievals are not
representative of the sky/atmosphere.

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

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

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

SGP/MWR/C1 - Intermittent Negative Sky Brightness Temperatures

Several related and recurring problems with the SGP 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 (especially at Purcell),
spikes in the data (especially at Vici), 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 (especially at the CF).

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 has 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.

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

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

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

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