SGP/MWR/B1 - 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 became active at SGP.B1 20020412.1600.  The 
MONORTM-based retrieval coefficients became active at SGP.B1 20050624.2100.

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.

• Mean total water vapor amount along LOS path(vap)
• 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 total water vapor amount along LOS path(vap)
• Mean total liquid water amount along LOS path(liq)

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

• Ensemble average for MWR liquid in window centered about balloon release(mean_liq_mwr)
• Ensemble average for MWR vapor in window centered about balloon release(mean_vap_mwr)

SGP/MWR/B1 - thermal instability

During periods of high ambient temperature, the instrument may have been thermally 
unstable. The problem was corrected by increasing the RF deck temperature from 50 to 52 C.

• Mean total liquid water amount along LOS path(liq)
• 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)

• Total liquid water along zenith path using tip-derived brightness temperatures(liqtip)
• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)
• 31.8 GHz sky brightness temperature derived from tip curve(tbskytip31)
• 23.8 GHz sky brightness temperature derived from tip curve(tbskytip23)

SGP/MWR/B1 - Reprocess: mixer temp adjustment

The RF deck temperature was increased from 50 to 52 C to prevent thermal instability in 
summer.  This resulted in a change in the calibration.  The data need to be reprocessed 
with the calibration coefficients that were automatically derived after the reference 
temperature, tkmx, was adjusted.

• Temperature correction coefficient at 23.8 GHz(tc23)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• Total liquid water along zenith path using tip-derived brightness temperatures(liqtip)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)
• 31.8 GHz sky brightness temperature derived from tip curve(tbskytip31)
• Temperature correction coefficient at 31.4 GHz(tc31)
• 23.8 GHz sky brightness temperature derived from tip curve(tbskytip23)

• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• Mean 23.8 GHz sky brightness temperature(tbsky23)
• Temperature correction coefficient at 31.4 GHz(tc31)
• Mean total liquid water amount along LOS path(liq)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Temperature correction coefficient at 23.8 GHz(tc23)
• Mean total water vapor amount along LOS path(vap)

SGP/MWR/B1 - New software version (4.15) installed

A problem began with the installation of MWR.EXE version 4.12 in July 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 at 21:25. As a consequence 
of this upgrade, the tip curve frequency increased. The tip cycle time decreased from 
~60s to ~50s.

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

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