NIM/MPL/M1 - False Positive Cloud Base Height Values During Solar Noon

As the laser ages, the output reduces.  This lowers the signal to noise ratio. The lower 
signal to noise ratio interferes with the cloud base height algorithm to correctly 
determine if a cloud is actually present. During solar noon the signal to noise ratio is the 
lowest. This condition results in many false positive values. The values start at a high 
altitude and progressively get lower as the sun gets to zenith. The trend reverses as the 
sun passes. The pattern in the data resembles a ?V? shape starting 2 hours before solar 
noon to 2 hour past. A low incident of false positive values exists from 20051227. However, 
the condition becomes prominent on 20060303 - 20060420. The cloud base calibration table 
was modified to compensate for the lower signal to noise levels. 

Note: If a cloud is actually present, the cloud base algorithm will determine the height 
and report correctly. The false positive values are only a concern during cloud free 
conditions.

• null(Raw data stream - documentation not supported)

• Preliminary cloud base height(preliminary_cbh)

NIM/MWR/M1 - Instrument noise problem/RF interference

Data are affected by intermittent spikes that become more frequent starting in March 2006. 
Spikes affect data mostly around 9 AM and 18:00 PM. The origin of the spikes is probably 
RF interference.

• 31.4 GHz sky brightness temperature derived from tip curve(tbsky31tip)
• 31.4 GHz sky signal(tipsky31)
• 23.8 GHz sky brightness temperature derived from tip curve(tbsky23tip)
• Total liquid water along zenith path using tip-derived brightness temperatures(liqtip)
• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)
• 23.8 GHz sky signal(tipsky23)

• null(Raw data stream - documentation not supported)

• Averaged total liquid water along LOS path(liq)
• MWR column precipitable water vapor(vap)
• 31.4 GHz sky signal(sky31)
• Sky brightness temperature at 23.8 GHz(tbsky23)
• Sky brightness temperature at 31.4 GHz(tbsky31)
• 23.8 GHz sky signal(sky23)

NIM/MWR/M1 - Reprocessed: Recalibration to correct for occasional overheating.

The radiometer was intermittently thermally unstable resulting in poor calibrations for 
four brief time periods.  These data have been reprocessed to apply corrected calibrations. 
 The affected time periods were:

20060302-20060303
20060423-20060425
20060512-20060515
20060531-20060603

• 23.8 GHz blackbody+noise injection signal(bbn23)
• 31.4 GHz blackbody(bb31)
• Temperature correction coefficient at 23.8 GHz(tc23)
• Noise injection temp at 31.4 GHz adjusted to tkbb(tnd31)
• 31.4 GHz goodness-of-fit coefficient(r31)
• Noise injection temp at nominal temperature at 31.4 GHz(tnd_nom31)
• (tknd)
• Mixer kinetic (physical) temperature(tkxc)
• 23.8 GHz Blackbody signal(bb23)
• 31.4 GHz sky brightness temperature derived from tip curve(tbsky31tip)
• 31.4 GHz blac2body+noise injection signal(bbn31)
• 23.8 GHz sky brightness temperature derived from tip curve(tbsky23tip)
• 31.4 GHz sky signal(tipsky31)
• Noise injection temp at nominal temperature at 23.8 GHz(tnd_nom23)
• Temperature correction coefficient at 31.4 GHz(tc31)
• 23.8 GHz goodness-of-fit coefficient(r23)
• Noise injection temp at 23.8 GHz adjusted to tkbb(tnd23)
• Total liquid water along zenith path using tip-derived brightness temperatures(liqtip)
• Blackbody kinetic temperature(tkbb)
• Total water vapor along zenith path using tip-derived brightness temperatures(vaptip)
• 23.8 GHz sky signal(tipsky23)

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

NIM/MWR/M1 - Sun in field of view of radiometer

Around 12 pm every day between 8/1 and 8/31 there is an increase in the brightness 
temperature due to the sun being in the field of view of the radiometer.

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