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.

• AVHRR satellite images for Darwin from BOM (RAW)(raw)

• Water vapor, total precipitable, derived from Tbright using stat. retrvl.(totalPrecipitableWater)
• Density, water vapor, prof. from sfc.-10 km, der. from Tbright stat. retrvl.(waterVaporDensity)
• Liquid water path, from Tbright at 23.835 and 30.0 GHz only, using stat. retrvl.(liquidWaterPath2)
• Microwave brightness temperature(brightnessTemperature)
• Retrieved dewpoint temperature(dewpointTemperature)
• Humidity, relative, prof. from sfc.-10km, from water vap. dens. and temp. prof.(relativeHumidity)
• Liquid water path, from brightness temperatures using statistical retrieval(liquidWaterPath)
• Liquid water content, cloud, vert. prof. sfc.-10km, from Tbright stat. retrvl.(liquidWaterContent)
• Temperature, virtual, vert. prof. sfc-10km, fr. wtr. vap. dens. and temp. prof.(virtualTemperature)
• Water vapor, tot. precipitable, from Tbright, 23.835 & 30.0 GHz, stat. retrvl.(totalPrecipitableWater2)
• Air temperature(temperature)
• Retrieved water vapor mixing ratio(waterVaporMixingRatio)

• AVHRR satellite images for Darwin from BOM (RAW)(raw)

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.

• tbsky31tip
• tbsky23tip
• tipsky31
• liqtip
• vaptip
• tipsky23

• Raw data stream - documentation not supported

• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• sky31
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• 31.4 GHz sky brightness temperature(tbsky31)
• sky23

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.

• AVHRR satellite images for Darwin from BOM (RAW)(raw)

• infraredTemperature

• AVHRR satellite images for Darwin from BOM (RAW)(raw)

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.

• Water vapor, total precipitable, derived from Tbright using stat. retrvl.(totalPrecipitableWater)
• liquidWaterPathRmsError
• liquidWaterPath2RmsError
• waterVaporDensityRmsError
• totalPrecipitableWater2RmsError
• temperatureRmsError
• Density, water vapor, prof. from sfc.-10 km, der. from Tbright stat. retrvl.(waterVaporDensity)
• Liquid water path, from Tbright at 23.835 and 30.0 GHz only, using stat. retrvl.(liquidWaterPath2)
• liquidWaterContentRmsError
• Retrieved dewpoint temperature(dewpointTemperature)
• totalPrecipitableWaterRmsError
• Humidity, relative, prof. from sfc.-10km, from water vap. dens. and temp. prof.(relativeHumidity)
• Liquid water path, from brightness temperatures using statistical retrieval(liquidWaterPath)
• Temperature, virtual, vert. prof. sfc-10km, fr. wtr. vap. dens. and temp. prof.(virtualTemperature)
• Liquid water content, cloud, vert. prof. sfc.-10km, from Tbright stat. retrvl.(liquidWaterContent)
• Height, cloud base, height where IR temp. matches retrieved temp. profile(cloudBaseHeight)
• Water vapor, tot. precipitable, from Tbright, 23.835 & 30.0 GHz, stat. retrvl.(totalPrecipitableWater2)
• Air temperature(temperature)
• Retrieved water vapor mixing ratio(waterVaporMixingRatio)

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/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

• bbn23
• bb31
• tc23
• tnd31
• r31
• tnd_nom31
• tknd
• tkxc
• bb23
• bbn31
• tbsky31tip
• tipsky31
• tbsky23tip
• tnd_nom23
• tc31
• r23
• tnd23
• liqtip
• tkbb
• vaptip
• tipsky23

• tkxc
• bb31
• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• bbn23
• sky23
• tkbb
• tnd31
• tnd_nom23
• tc31
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)
• tknd
• bbn31
• sky31
• bb23
• 31.4 GHz sky brightness temperature(tbsky31)
• tnd_nom31
• tc23
• 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.

• Radiation, longwave, brightness temperature, 23.8 GHz(tbsky23)
• 31.4 GHz sky brightness temperature(tbsky31)
• Total liquid water along LOS path(liq)
• Total water vapor along LOS path(vap)

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

• Microwave brightness temperature(brightnessTemperature)
• Water vapor, total precipitable, derived from Tbright using stat. retrvl.(totalPrecipitableWater)
• totalPrecipitableWaterRmsError
• liquidWaterPathRmsError
• infraredTemperature
• liquidWaterPath2RmsError
• Liquid water path, from brightness temperatures using statistical retrieval(liquidWaterPath)
• totalPrecipitableWater2RmsError
• Liquid water content, cloud, vert. prof. sfc.-10km, from Tbright stat. retrvl.(liquidWaterContent)
• Water vapor, tot. precipitable, from Tbright, 23.835 & 30.0 GHz, stat. retrvl.(totalPrecipitableWater2)
• Liquid water path, from Tbright at 23.835 and 30.0 GHz only, using stat. retrvl.(liquidWaterPath2)
• liquidWaterContentRmsError

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

• infraredTemperature

NIM/RWP/M1 - Reprocess: Wind direction offset

A strong wind storm on June 17, 2006 toppled the RWP antenna.  After repair and 
reinstallation, the wind direction reported by the instrument was rotated counterclockwise 90 
degrees, possibly because the antenna was installed rotated by 90 deg.  This condition 
continued through the remainder of deployment.

All wind direction values need to be increased by 90 degrees.

• Eastward Wind Component(u_wind)
• Northward Wind Component(v_wind)

NIM/MET/M1 - ORG underestimated precipitation

The ORG underestimated precipitation by about 38% during the entire NIM deployment.  No 
troubleshooting technique or replacement of gauge was successful in correcting the problem.

• ORG precipitation rate mean(org_precip_rate_mean)

NIM/MET/M1 - Wind Speed data contain offset due to induced voltage

The marine model of the RM Young wind sensor needs twisted pair shielded cable.  The 
manufacturer did not originally supply the pigtail with twisted pair shielded cable.  Use of 
twisted pair shielded cable for the rest of the cable run to the logger was also not 
specified.  This caused an induced voltage in the wind speed line from the wind direction 
excitation.  The induced voltage varied from sensor to sensor and probably changed anytime 
the cable was replaced or parts of the wind sensor were repaired or replaced. The induced 
voltage has been seen to vary from 0.15 m/s to as much as 1.08 m/s.

• Wind speed vector mean(wspd_vec_mean)
• Wind speed, lower, 1-min avg(wspd_arith_mean)

NIM/MET/M1 - PWD cumulative precipitation incorrect

The Present Weather Detector is a serial sensor.  The MET system datalogger reads in the 
data from this sensor.  During the time in question serial comms problems were causing the 
data from the sensor to be read incorrectly.  The data for one variable showed up in 
data for another variable or not at all.  We reprocessed the data to correct as much of this 
error as we could.  The cumulative rainfall variable was calculated from the 
instantaneous rainfall variable during reprocessing.  Since we cannot be entirely sure all 
cumulative rainfall values are correct or were completely captured the cumulative rainfall data is 
considered to be unreliable.  This issue shows up when comparing the cumulative rainfall 
data at the end of the day 07/31/2006 (79.08) and the beginning of the next day 
08/01/2006 (3.17).  Clearly we were either under or over-estimating the cumulative rainfall.

• pwd_cumul_rain

NIM/MET/M1 - PWD 1 minute rainfall data suspect

The Present Weather Detector is a serial sensor.  The MET system datalogger reads in the 
data from this sensor.  During the time in question serial comms problems were causing the 
data from the sensor to be read incorrectly.  The data for one variable showed up in 
data for another variable or not at all.  We reprocessed the data to correct as much of this 
error as we could. We cannot be entirely certain that all rainfall values are correct or 
were captured properly.  It is possible that some values were missed completely.

• pwd_precip_rate_mean_1min