NSA/MWR/C1 - Temperature Stabilization of Noise Diode Impaired

On 1/17 we had a big spike in the data and lost temperature stabilization. The instrument 
had problems maintaining the Noise Diode (ND) temperature since. At ambient temperatures 
under about -20 C the ND was not maintaining the set temperature of 30 C. This problem 
was reported in P010122.1.

Fred Solheim recommended on 1/22 that we powercycle the instrument as it looked like the 
instrument CPU had lost the temperature reference.

So we powercycled the instrument on 1/22 @ 20:30 and lost all comumnication to it; after a 
second powercycling the instrument came back on line and the temperature stabilized 
quickly (within a couple of minutes) to the set temperature (30 C)

Fred Solheim reported after the system was restored:
"I've never seen this behavior before. I don't think it was due to the RF deck physically 
hanging temperature, because the recorded temp dropped about 30 C in one observation 
cycle. If this happens again, send the MWR down along with data files for us to look at."

Data collected in the periode 1/17/2001 6:00 to 1/22/2001 21:45 are questionable since it 
is uncertain whether the temperature really was unstable and what really caused the 
problem.

• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• 23.8 GHz sky signal(sky23)
• Mean IR brightness temperature(ir_temp)
• Mean total liquid water amount along LOS path(liq)
• Mean 23.8 GHz sky brightness temperature(tbsky23)
• Noise diode mount temperature(tknd)
• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• 31.4 GHz blackbody+noise injection signal(bbn31)
• Temperature correction coefficient at 23.8 GHz(tc23)
• 31.4 GHz sky signal(sky31)
• Temperature correction coefficient at 31.4 GHz(tc31)
• Ambient temperature(tkair)
• 31.4 GHz Blackbody signal(bb31)
• Blackbody kinetic temperature(tkbb)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Mean total water vapor amount along LOS path(vap)
• 23.8 GHz blackbody+noise injection signal(bbn23)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• Mixer kinetic (physical) temperature(tkxc)
• 23.8 GHz Blackbody signal(bb23)

• Mean 23.8 GHz sky brightness temperature(tbsky23)
• Standard deviation about the mean for the IR brightness temperature(ir_temp_sdev)
• Number of points included in the ir_temp ensemble(num_obs_irt)
• Standard deviation about the mean for the 23.8 GHz sky brightness temperature(tbsky23_sdev)
• Fraction of data in averaging interval with water on the Teflon window(water_flag_fraction)
• Mean IR brightness temperature(ir_temp)
• Standard deviation about the mean for the 31.4 GHz sky brightness temperature(tbsky31_sdev)
• Standard deviation about the mean for the total liquid water amount(liq_sdev)
• Number of points included in the ensemble of all the fields except the ir_temp
  fields(num_obs)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Mean total water vapor amount along LOS path(vap)
• Mean total liquid water amount along LOS path(liq)
• Standard deviation about the mean for the total water vapor amount(vap_sdev)

• Mean total water vapor amount along LOS path(vap)
• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• Mean total liquid water amount along LOS path(liq)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Mean IR brightness temperature(ir_temp)
• Mean 23.8 GHz sky brightness temperature(tbsky23)

NSA/MWR/C1 - Reprocess: Revised Calibration 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 NSA.C1 
20020425.1900.  The MONORTM-based retrieval coefficients became active 
at NSA.C1 20050629.0000.

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

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

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

NSA/MWR/C1 - Missing Data

Instrument was removed for repair.

• Mean 23.8 GHz sky brightness temperature(tbsky23)
• Fraction of data in averaging interval with water on the Teflon window(water_flag_fraction)
• Time offset of tweaks from base_time(time_offset)
• Standard deviation about the mean for the total liquid water amount(liq_sdev)
• east longitude for all the input platforms.(lon)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Standard deviation about the mean for the IR brightness temperature(ir_temp_sdev)
• Number of points included in the ir_temp ensemble(num_obs_irt)
• Standard deviation about the mean for the 23.8 GHz sky brightness temperature(tbsky23_sdev)
• north latitude for all the input platforms.(lat)
• Mean IR brightness temperature(ir_temp)
• Standard deviation about the mean for the 31.4 GHz sky brightness temperature(tbsky31_sdev)
• Number of points included in the ensemble of all the fields except the ir_temp
  fields(num_obs)
• Mean total water vapor amount along LOS path(vap)
• Mean total liquid water amount along LOS path(liq)
• altitude above sea levelaltunits(alt)
• Time offset from base_time(base_time)
• Standard deviation about the mean for the total water vapor amount(vap_sdev)

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

• Actual elevation angle(actel)
• Actual Azimuth(actaz)
• 31.4 GHz Blackbody signal(bb31)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• north latitude for all the input platforms.(lat)
• Sky/Cloud Infra-Red Temperature(sky_ir_temp)
• 23.8 GHz blackbody+noise injection signal(bbn23)
• Mean 31.4 GHz sky brightness temperature(tbsky31)
• Noise diode mount temperature(tknd)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• Mean IR brightness temperature(ir_temp)
• Ambient temperature(tkair)
• Temperature correction coefficient at 31.4 GHz(tc31)
• Time offset from base_time(base_time)
• Blackbody kinetic temperature(tkbb)
• Mean total water vapor amount along LOS path(vap)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• 23.8 GHz Blackbody signal(bb23)
• 31.4 GHz blackbody+noise injection signal(bbn31)
• Time offset of tweaks from base_time(time_offset)
• 31.4 GHz sky signal(sky31)
• east longitude for all the input platforms.(lon)
• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• Mean total liquid water amount along LOS path(liq)
• Mixer kinetic (physical) temperature(tkxc)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• altitude above sea levelaltunits(alt)
• 23.8 GHz sky signal(sky23)
• Mean 23.8 GHz sky brightness temperature(tbsky23)
• Temperature correction coefficient at 23.8 GHz(tc23)

• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Noise diode mount temperature(tknd)
• 23.8 GHz sky signal(tipsky23)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• Mixer kinetic (physical) temperature(tkxc)
• 23.8 GHz sky brightness temperature derived from tip curve(tbskytip23)
• 31.4 GHz sky signal(tipsky31)
• Actual elevation angle(actel)
• Noise injection temp at 23.8 GHz derived from this tip(tnd23I)
• Water on Teflon window (1=WET, 0=DRY)(wet_window)
• Total liquid water along zenith path using tip-derived brightness temperatures(liqtip)
• Noise injection temp at 31.4 GHz derived from this tip(tnd31I)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• Actual Azimuth(actaz)
• 23.8 GHz goodness-of-fit coefficient(r23)
• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)
• 31.4 GHz blackbody+noise injection signal(bbn31)
• 23.8 GHz blackbody+noise injection signal(bbn23)
• Temperature correction coefficient at 31.4 GHz(tc31)
• Time offset from base_time(base_time)
• east longitude for all the input platforms.(lon)
• 31.4 GHz goodness-of-fit coefficient(r31)
• Ambient temperature(tkair)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• Temperature correction coefficient at 23.8 GHz(tc23)
• Time offset of tweaks from base_time(time_offset)
• altitude above sea levelaltunits(alt)
• 31.4 GHz Blackbody signal(bb31)
• 23.8 GHz Blackbody signal(bb23)
• 31.8 GHz sky brightness temperature derived from tip curve(tbskytip31)
• Blackbody kinetic temperature(tkbb)
• north latitude for all the input platforms.(lat)