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.

• Preliminary cloud base height(preliminary_cbh)

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

NIM/MWRP/M1 - Software problem

The MWRP computer failed and it was cloned with a new Gx620. Soon after, the MWRP program 
started to crash and was intermittent. Data were lost on March 3, 4, 5. 
On March 7 the program was forcefully ended and restarted. This appears to have cleared 
the problem. The instrument has been running since.

• Raw data stream - documentation not supported(raw)

• Level of free convection pressure(levelFreeConvectionPres)
• lon(lon)
• Time offset of tweaks from base_time(time_offset)
• time(time)
• Expected root-mean-square error in liquid water path retrieval(liquidWaterPathRmsError)
• azimuth(azimuth)
• Expected root-mean-square error in liquid water content retrieval(liquidWaterContentRmsError)
• Lifting condensation level pressure(liftingCondensationLevelPres)
• Retrieved cloud liquid water content(liquidWaterContent)
• Surface relative humidity at instrument(surfaceRelativeHumidity)
• Dummy altitude for Zeb(alt)
• Lifting condensation level(liftingCondensationLevel)
• Interpolated water vapor mixing ratio(waterVaporMixingRatio)
• Derived virtual temperature(virtualTemperature)
• elevation(elevation)
• Convective Available Potential Energy(cape)
• air temperature (NGM250 predicted)(temperature)
• Internal blackbody reference temperature(blackbodyTemperature)
• Zenith-pointing infrared temperature at 10um(infraredTemperature)
• Level of free convection(levelFreeConvection)
• Flag indicating moisture sensor status(wetWindowFlag)
• Cloud base height(cloudBaseHeight)
• Retrieved total precipitable water vapor using only 23.835 and 30.0 GHz(totalPrecipitableWater2)
• Microwave brightness temperature(brightnessTemperature)
• Equilibrium level(equilibriumLevel)
• base time(base_time)
• atmospheric pressure at mean sea level and at tropopause (NGM250 predicted)(pressure)
• Equilibrium level pressure(equilibriumLevelPres)
• Surface absolute temperature at instrument(surfaceTemperature)
• Surface water vapor density at instrument(surfaceWaterVaporDensity)
• Expected root-mean-square error in liquid water path retrieval using only 23.835
  and 30.0 GHz(liquidWaterPath2RmsError)
• Surface pressure at instrument(surfacePressure)
• Derived relative humidity(relativeHumidity)
• Array of heights for the range gates(height)
• Expected root-mean-square error in precipitable water retrieval(totalPrecipitableWaterRmsError)
• Expected root-mean-square error in water vapor density retrieval(waterVaporDensityRmsError)
• lat(lat)
• Retrieved liquid water path using only 23.835 and 30.0 GHz(liquidWaterPath2)
• Data quality flags(dataQualityFlags)
• Interpolated dewpoint temperature(dewpointTemperature)
• Frequency(frequency)
• Retrieved water vapor density(waterVaporDensity)
• Retrieved liquid water path(liquidWaterPath)
• Expected root-mean-square error in temperature retrieval(temperatureRmsError)
• Expected root-mean-square error in precipitable water retrieval using only
  23.835 and 30.0 GHz(totalPrecipitableWater2RmsError)
• Total precipitable water vapor, from microwave radiometer(totalPrecipitableWater)

• Raw data stream - documentation not supported(raw)

NIM/TSI/M1 - Reprocess: incorrect daily movies

Due to file management problems on the operating computer, the daily movie files are 
either missing, incomplete, or contain images from other days.

• (MPEG data stream - documentation not yet available)

NIM/MWRP/M1 - Instrument noise problem

There are spikes and elevated noise in MWRP data. The origine of the spikes is RF 
interference from various sources.  All brightness temperatures are affected, but in particular 
the 5 K-band channels. LWP retrievals are noisy and affected by spikes as a result.

• Raw data stream - documentation not supported(raw)

• Retrieved cloud liquid water content(liquidWaterContent)
• Derived relative humidity(relativeHumidity)
• Derived virtual temperature(virtualTemperature)
• Interpolated water vapor mixing ratio(waterVaporMixingRatio)
• Retrieved liquid water path using only 23.835 and 30.0 GHz(liquidWaterPath2)
• air temperature (NGM250 predicted)(temperature)
• Retrieved water vapor density(waterVaporDensity)
• Interpolated dewpoint temperature(dewpointTemperature)
• Retrieved liquid water path(liquidWaterPath)
• Retrieved total precipitable water vapor using only 23.835 and 30.0 GHz(totalPrecipitableWater2)
• Microwave brightness temperature(brightnessTemperature)
• Total precipitable water vapor, from microwave radiometer(totalPrecipitableWater)

• Raw data stream - documentation not supported(raw)

NIM/MWRP/M1 - IRT Sensor Calibration

Discrepancies between the MWRP and Skyrad IRT were observed in January. The MWRP IRT 
readings were constantly higher than those of the skyrad IRT. Some changes were introduced to 
the MWRP IRT to address the problem (see DQR D060602.2). On May 3, the IRT mirror was 
replaced. After the change in the mirror, the MWRP IRT readings became about 5-8 C lower. On 
June 3 the agreement between MWRP and Skyrad IRT became satisfactory (2-5 degree C 
difference).

It is hard to numerically quantify the difference in the IRT readings caused by the change 
in the mirror. We can only warn the user that between January 1 and June 3 the MWRP 
readings are 8 to 15 degree higher than the skyrad IRT.

• Raw data stream - documentation not supported(raw)

• Zenith-pointing infrared temperature at 10um(infraredTemperature)

• Raw data stream - documentation not supported(raw)

NIM/MWRP/M1 - Reprocessed: IRT configuration setting error

The infrared thermometer settings (IRT) were not configured as specified by the 
manufacturer. The analog output was set to a range of -60 to +50 C (0-10V) instead of -50 to +50 C 
(0-10V). The settings were changed on April 20. The IR temperatures should be slightly 
smaller than reported.

The data have been reprocessed to correct the IRT calibrations.  Reprocessed data were 
archived in August 2006.

• Zenith-pointing infrared temperature at 10um(infraredTemperature)

NIM/MWRP/M1 - Reprocessed - New retrieval coefficients

Occasionally, the retrieved relative humidity was exceeding 120%. Upon reviewing the data 
it was noticed that the high values were appearing in the highest layers (above 8 km) and 
especially during spring season. Since retrievals at the highest levels are mainly 
affected by the climatology used to constrain the retrievals, we reviewed the statistical 
coefficients that were used to retrieve temperature and humidity. It was discovered that, in 
the training dataset (radiosonde), there were a few outliers (invalid radiosonde 
soundings) that had escaped the screening process and were affecting the computations of the 
retrieval coefficients.

We recomputed the retrieval coefficients with the newly screened set of radiosonde data 
and reprocessed all the previous data at Niamey.  The reprocessed data were archived in 
August 2006.

The new coefficients improve temperature and humidity profiles in two ways. The relative 
humidity will not exceed 120% in the upper layers and the temperature profiles will be in 
better agreement with the sonde in the first 4 km.

• Expected root-mean-square error in liquid water path retrieval(liquidWaterPathRmsError)
• Expected root-mean-square error in liquid water content retrieval(liquidWaterContentRmsError)
• Expected root-mean-square error in liquid water path retrieval using only 23.835
  and 30.0 GHz(liquidWaterPath2RmsError)
• Retrieved cloud liquid water content(liquidWaterContent)
• Derived relative humidity(relativeHumidity)
• Derived virtual temperature(virtualTemperature)
• Interpolated water vapor mixing ratio(waterVaporMixingRatio)
• Expected root-mean-square error in precipitable water retrieval(totalPrecipitableWaterRmsError)
• Expected root-mean-square error in water vapor density retrieval(waterVaporDensityRmsError)
• Retrieved liquid water path using only 23.835 and 30.0 GHz(liquidWaterPath2)
• air temperature (NGM250 predicted)(temperature)
• Retrieved water vapor density(waterVaporDensity)
• Interpolated dewpoint temperature(dewpointTemperature)
• Retrieved liquid water path(liquidWaterPath)
• Cloud base height(cloudBaseHeight)
• Retrieved total precipitable water vapor using only 23.835 and 30.0 GHz(totalPrecipitableWater2)
• Expected root-mean-square error in temperature retrieval(temperatureRmsError)
• Expected root-mean-square error in precipitable water retrieval using only
  23.835 and 30.0 GHz(totalPrecipitableWater2RmsError)
• Total precipitable water vapor, from microwave radiometer(totalPrecipitableWater)

NIM/GNDRAD/M1 - Reprocessed: Longwave calibration error

Modified pyrgeometer calibration procedures were implemented beginning in December 2003. 
These modified procedures introduced a calibration bias in the longwave data.  The 
previous procedures were re-implemented at all sites between December 2005 and February 2006 to 
restore proper calibrations.									     
The data collected while the incorrect procedures were in place have been reprocessed to 
remove the calibration bias.  The reprocessed 60 second averaged data are based on 3 
instantaneous 20 second data records rather than on 60 1 second instantaneous data records.  
Still, these data are considered far superior to the originally processed data. The 
reprocessed data were archived in February 2007.

• Upwelling (10 meter) Longwave Hemispheric Irradiance, Pyrgeometer(up_long_hemisp)

NIM/MWRP/M1 - 51.25 GHz channel calibration drifted

After a power outage on May 5 the 51.25 GHz had a slight change in the calibration. The 
resulting LWP computed by using all 6 channels increased of about 0.025 mm (25 g/m2).

• Microwave brightness temperature(brightnessTemperature)

NIM/TSI/M1 - Shadowband Misalignment

From installation, the shadowband was positioned south at solar noon until the vernal 
equinox when it began to migrate counter-clockwise until reaching east 37 days later on 4/26 
(about 9 days before mid-spring). The shadowband at solar noon continued to migrate until 
reaching its most northerly position (~15 deg) on the summer solstice (if everything was 
perfectly aligned, it probably would have been pointed north on this day). It then began 
to migrate clockwise and reached east again 56 days later on 8/16 (about 14 days after 
mid-summer). As expected, the shadowband reached its most southerly position on the 
autumnal equinox but was about 10 deg off of being due south. 

With the apparent alignment problem, I don't understand why the shadowband was mostly 
blocking the sun. When I started noticing this offset in May, I chose to leave it alone 
because I felt that adjusting the shadowband to where I thought it should be would cause it to 
not block the sun at either sunrise or sunset. 

The alignment was corrected on 9/29 (6 days after the day of the autumnal equinox).

• JPG data stream - documentation not supported(JPEG data stream - documentation not yet available)

• PNG data stream - documentation not supported(png)

• (MPEG data stream - documentation not yet available)

NIM/MWRP/M1 - Sun in radiometer's field of view

Around noon local time every day there is a spike in the brightness temperature data. This 
is due to the sun being in the field of view of the radiometer. PWV and LWP are affected 
as a consequence

• Expected root-mean-square error in precipitable water retrieval(totalPrecipitableWaterRmsError)
• Expected root-mean-square error in liquid water path retrieval(liquidWaterPathRmsError)
• Retrieved liquid water path using only 23.835 and 30.0 GHz(liquidWaterPath2)
• Expected root-mean-square error in liquid water content retrieval(liquidWaterContentRmsError)
• Zenith-pointing infrared temperature at 10um(infraredTemperature)
• Retrieved liquid water path(liquidWaterPath)
• Expected root-mean-square error in liquid water path retrieval using only 23.835
  and 30.0 GHz(liquidWaterPath2RmsError)
• Retrieved total precipitable water vapor using only 23.835 and 30.0 GHz(totalPrecipitableWater2)
• Microwave brightness temperature(brightnessTemperature)
• Retrieved cloud liquid water content(liquidWaterContent)
• Expected root-mean-square error in precipitable water retrieval using only
  23.835 and 30.0 GHz(totalPrecipitableWater2RmsError)
• Total precipitable water vapor, from microwave radiometer(totalPrecipitableWater)

NIM/MWRP/M1 - IRTs do not agree with AERI

Since deployment at PYE, and then at NIM, the AMF SKYRAD IRT measured about 10K higher sky 
temperatures than the AERI and the MWRP IRT measured about 20K higher than the AERI.  
Several actions were taken to diagnose the problem including confirming the correct 
configuration of the IRTs and data logger, cleaning the mirror and lens, and replacing the mirror.

After several days of rain beginning 6/2/2006, the three instruments came into agreement. 
The cause of the discrepancy was probably dust accumulation on the lens of the instrument

• Zenith-pointing infrared temperature at 10um(infraredTemperature)

NIM/MWRP/M1 - Reprocessed: K-band calibration drift corrected

During October and November there was a drift in the K-Band calibration of the MWRP. This 
resulted in brightness temperatures that were too high.

New calibration coefficients were derived from the median value of the noise diode 
temperature for the months of October and November and the data were reprocessed to apply the 
corrected calibrations.  The reprocessed data were archived in January 2007.

• Retrieved liquid water path using only 23.835 and 30.0 GHz(liquidWaterPath2)
• Retrieved liquid water path(liquidWaterPath)
• Retrieved total precipitable water vapor using only 23.835 and 30.0 GHz(totalPrecipitableWater2)
• Microwave brightness temperature(brightnessTemperature)
• Retrieved cloud liquid water content(liquidWaterContent)
• Total precipitable water vapor, from microwave radiometer(totalPrecipitableWater)