SGP/MPL/C1 - Data missing due to hardware failures

The MPL instrument was out of service during the time
range specified due to hardware failures. Data during
this period are missing and unrecoverable.

• North latitude(lat)
• East longitude(lon)
• Pressure, associated geometric height, at altitude, NGM model output(height)
• range_offset
• range
• shots_sum
• laser_scalar_sync_offset
• Preliminary cloud base height(preliminary_cbh)
• filter_temp
• voltage_05
• trigger_freq
• time
• max_altitude
• range_bins
• energy_monitor
• detector_temp
• transceiver_altitude_angle
• shots_summed
• deadtime_correction
• voltage_15
• Altitude above mean sea level(alt)
• property
• voltage_10
• range_bin_width
• pulse_rep
• Backscatter, ceilometer, range and sensitivity corrected(backscatter)
• laser_sync_offset
• range_bin_time
• laser_temp
• time_offset
• base_time
• scalar_sync_offset
• instrument_temp
• total_counts
• background_signal
• transceiver_azimuth_angle

SGP/MPL/C1 - Signal degrading

The MPL viewport window was blown off during a storm on 2002/09/25.  The MPL received a 
soaking of rain.  Following this event, although site operations cleaned and dried the 
optics, the lidar performance continued to degrade over the next few months.  Although 
initially suitable for cloud detection, by Dec 10th the lidar was providing useful results only 
during the day (oddly enough).  By Jan 16, the detector was dead.  

It is not recommended to depend on night-time cloud base heights after Dec. 10 2002. 

It is not recommended to use any of the data after 9/25 for aerosol retrievals.

• North latitude(lat)
• East longitude(lon)
• Pressure, associated geometric height, at altitude, NGM model output(height)
• range_offset
• range
• shots_sum
• laser_scalar_sync_offset
• Preliminary cloud base height(preliminary_cbh)
• filter_temp
• voltage_05
• trigger_freq
• time
• max_altitude
• range_bins
• energy_monitor
• detector_temp
• transceiver_altitude_angle
• shots_summed
• deadtime_correction
• voltage_15
• Altitude above mean sea level(alt)
• property
• voltage_10
• range_bin_width
• pulse_rep
• Backscatter, ceilometer, range and sensitivity corrected(backscatter)
• laser_sync_offset
• range_bin_time
• laser_temp
• time_offset
• base_time
• scalar_sync_offset
• instrument_temp
• total_counts
• background_signal
• transceiver_azimuth_angle

SGP/MPL/C1 - Detector Failure

The detector failed following a period of data quality degradation.  The MPL was replaced 
on 1/31/2003.

• North latitude(lat)
• East longitude(lon)
• Pressure, associated geometric height, at altitude, NGM model output(height)
• range_offset
• range
• shots_sum
• laser_scalar_sync_offset
• Preliminary cloud base height(preliminary_cbh)
• filter_temp
• voltage_05
• trigger_freq
• time
• max_altitude
• range_bins
• energy_monitor
• detector_temp
• transceiver_altitude_angle
• shots_summed
• deadtime_correction
• voltage_15
• Altitude above mean sea level(alt)
• property
• voltage_10
• range_bin_width
• pulse_rep
• Backscatter, ceilometer, range and sensitivity corrected(backscatter)
• laser_sync_offset
• range_bin_time
• laser_temp
• time_offset
• base_time
• scalar_sync_offset
• instrument_temp
• total_counts
• background_signal
• transceiver_azimuth_angle

SGP/MPL/C1 - Metadata errors

The latitude, longitude and altitude of the Micropulse Lidar
(MPL) were incorrectly entered into the ARM database.  The 
correct location of the SGP.C1 MPL is:
   Lat: 36.606N
   Lon: 97.485W
   Alt:    316m

• North latitude(lat)
• Altitude above mean sea level(alt)
• East longitude(lon)

SGP/MPL/C1 - Reduced detection sensitivity

During the time periods indicated, the laser power supply was low.  This resulted in 
compromised detection sensitivity, particularly for thin clouds and/or during daylight hours.  
That is, some clouds may not have been identified.  The low laser power would not have 
resulted in false positives.

• Preliminary cloud base height(preliminary_cbh)

SGP/MPL/C1 - Sensor Calibration

The Energy Monitor records the value of the laser energy. During the time in question, the 
laser energy exceed the maximum value in the calibration table for the energy monitor. 
In other words, the value is pegged. This condition does not affect the backscatter 
signal. But it will prevent users from normalizing the backscatter signal to the laser output.

• energy_monitor

SGP/MPL/C1 - Instrument offline

Instrument was taken offline due to a failure of the laser power supply.  Data are missing 
and unrecoverable.

• North latitude(lat)
• East longitude(lon)
• Pressure, associated geometric height, at altitude, NGM model output(height)
• range_offset
• range
• shots_sum
• laser_scalar_sync_offset
• Preliminary cloud base height(preliminary_cbh)
• filter_temp
• voltage_05
• trigger_freq
• time
• max_altitude
• range_bins
• energy_monitor
• detector_temp
• transceiver_altitude_angle
• shots_summed
• deadtime_correction
• voltage_15
• Altitude above mean sea level(alt)
• property
• voltage_10
• range_bin_width
• pulse_rep
• Backscatter, ceilometer, range and sensitivity corrected(backscatter)
• laser_sync_offset
• range_bin_time
• laser_temp
• time_offset
• base_time
• scalar_sync_offset
• instrument_temp
• total_counts
• background_signal
• transceiver_azimuth_angle

SGP/MPL/C1 - Intermittent Double Pulse from MPL laser

When Spectra Physics discontinued support for their laser diode power supply, an 
alternative was needed to extend the usefulness of the Spectra Physics laser head inside the MPLs. 
 The solution was to use a Coherent laser diode. Unfortunately, the Coherent diode 
lasers do not have the exact same characteristics as the Spectra Physics diode lasers. As a 
result, the output of the Spectra Physics laser head sometimes produces a second pulse 
close in time but lower in intensity from the first main pulse. This is known as “double pulsing”.

Not all of the Spectra Physics/Coherent combination systems produce a double pulse and the 
systems that do produce a double pulse do not always exhibit this behavior. It can be 
identified by a second peak at ~.2km. At first glance the signal in the data will resemble 
a low aerosol or cloud layer. When the double pulse is weak, the atmospheric signal will 
obscure the double pulse signal. At the ARM sites with a sunshade such as TWP and AMF, 
the double pulse can be seen when the sunshade closes during solar noon. When the sunshade 
closes, the MPL does not see atmospheric signal so the second pulse is evident. At SGP, a 
daily window cleaning is part of the routine. During this time the double pulse can be 
seen. Without a sunshade or window cleaning it is impossible to say definitively if double 
pulse is present. 

The first system to produce a double pulse was MPL s/n 008 located at TWP – C2 Nauru in 
February 2005. The second system was MPL s/n 004 located at SGP in August 2005. The 
potential for the other systems to produce a double pulse is high. However, as of March 2006, 
the MPLs at NSA, TWP – C1, TWP – C3 and AMF have not recorded data with the double pulse 
artifact. 

The ARM program is in the process of replacing all the MPLs with a newer model. After the 
new MPLs are deployed the double pulse problem should not be an issue. The old systems 
will be relegated as spares. The double pulse problem will return if an old system is 
needed to replace a failed new system.

• detector_counts

SGP/MPL/C1 - Scope temperature incorrect

The scope_temp started to jump around on 6/29 at about 19:00 GMT between 24-32C.  Then 
~03:00 GMT on 6/30 the temperature exceeded the MAX flag value of 40C and was fluctuating 
between 150-225C.  

Temp probe connection was found to be loose and was reseated 20070806.

Ignore scope temp data and assume values are valid.

• scope_temp

SGP/MPL/C1 - Water intrusion

Instrument temperatures were incorrect.  On 02/01 and 02/03 they essentially flat lined at 
0 C, while on 02/02 the temps were lower than normal (although given the external temp 
they may be accurate), with several data spikes throughout the day.

Background signal values were excessively low throughout the entire period. Co- and 
cross-pol plotted values appear to have had a 3-5 km artificial elevation, resulting in plotted 
cloud bases appearing much higher than they actually were.

System was not operating correctly due to water intrusion.

• num_channels
• background_signal_co_pol
• range
• num_bins
• dead_time_corrected
• Pressure, associated geometric height, at altitude, NGM model output(height)
• pulse_rep
• background_signal_std_cross_pol
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• laser_temp
• first_data_bin
• background_signal_cross_pol
• overlap_correction
• detector_temp
• max_altitude
• range_bin_width
• Attenuated backscatter, copol(signal_return_co_pol)
• overlap_correction_heights
• mcs_mode
• polarization_control_voltage
• polarization_control
• deadtime_correction_counts
• background_signal_std_co_pol
• range_bin_time
• deadtime_correction
• range_bins
• energy_monitor
• range_offset
• Preliminary cloud base height(preliminary_cbh)
• HLN(VN)
• scope_temp

SGP/MPL/C1 - Instrument failure

Backscatter data were incorrect then instrument appears to fail entirely. On 
20130515.191731, a new file was created and data appears to be OK. 

Unknown problem but do not use data for specified period.

• Attenuated backscatter, cross pol(signal_return_cross_pol)
• background_signal_std_cross_pol
• background_signal_cross_pol
• Attenuated backscatter, copol(signal_return_co_pol)
• deadtime_correction_counts
• overlap_correction
• deadtime_correction
• background_signal_std_co_pol
• background_signal_co_pol
• overlap_correction_heights
• dead_time_corrected

SGP/MPL/C1 - Instrument problem

Data are incorrect.

• Pressure, associated geometric height, at altitude, NGM model output(height)
• range_offset
• laser_scalar_sync_offset
• Preliminary cloud base height(preliminary_cbh)
• filter_temp
• trigger_freq
• energy_monitor
• transceiver_altitude_angle
• voltage_15
• voltage_10
• pulse_rep
• Backscatter, ceilometer, range and sensitivity corrected(backscatter)
• laser_sync_offset
• range_bin_time
• laser_temp
• scalar_sync_offset
• instrument_temp
• total_counts
• background_signal
• detector_counts
• shots_sum
• range
• voltage_05
• max_altitude
• range_bins
• detector_temp
• shots_summed
• deadtime_correction
• assumed_zero_range_bin
• property
• range_bin_width
• transceiver_azimuth_angle

• num_channels
• background_signal_co_pol
• num_bins
• range
• qc_signal_return_co_pol
• qc_signal_return_cross_pol
• pulse_rep
• background_signal_std_cross_pol
• first_data_bin
• qc_energy_monitor
• qc_preliminary_cbh
• deadtime_correction_counts
• range_bin_time
• range_bins
• Preliminary cloud base height(preliminary_cbh)
• qc_laser_temp
• dead_time_corrected
• Pressure, associated geometric height, at altitude, NGM model output(height)
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• laser_temp
• background_signal_cross_pol
• qc_scope_temp
• overlap_correction
• detector_temp
• max_altitude
• range_bin_width
• Attenuated backscatter, copol(signal_return_co_pol)
• overlap_correction_heights
• qc_range_offset
• mcs_mode
• polarization_control_voltage
• polarization_control
• qc_detector_temp
• deadtime_correction
• background_signal_std_co_pol
• range_offset
• energy_monitor
• scope_temp

• Preliminary cloud base height(preliminary_cbh)
• range_bin_time
• detector_temp
• energy_monitor
• num_bins
• Pressure, associated geometric height, at altitude, NGM model output(height)
• range
• pulse_rep
• background_signal
• background_signal_std
• range_bin_width
• range_offset
• range_bins
• shots_per_avg
• signal_return
• num_channels
• dead_time_corrected
• laser_temp
• polarization_control_voltage
• max_altitude
• scope_temp
• polarization_control

SGP/MPL/C1 - Reprocessing Notice (RID 1304)

See below for details of reprocessing that was completed on 20160107.
Original DQR category: 0 (Black, Missing).

-----------------------------------------------------------

preliminary_cbh data are were never derived and are set to -9999.

• Preliminary cloud base height(preliminary_cbh)

SGP/MPL/C1 - Collection problem

No data available

• North latitude(lat)
• qc_laser_temp
• num_channels
• background_signal_co_pol
• qc_time
• range
• num_bins
• qc_signal_return_co_pol
• dead_time_corrected
• Pressure, associated geometric height, at altitude, NGM model output(height)
• pulse_rep
• qc_signal_return_cross_pol
• background_signal_std_cross_pol
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• laser_temp
• first_data_bin
• background_signal_cross_pol
• East longitude(lon)
• qc_scope_temp
• overlap_correction
• detector_temp
• qc_energy_monitor
• base_time
• range_bin_width
• max_altitude
• time_offset
• qc_preliminary_cbh
• Attenuated backscatter, copol(signal_return_co_pol)
• overlap_correction_heights
• qc_range_offset
• mcs_mode
• polarization_control_voltage
• polarization_control
• qc_detector_temp
• Altitude above mean sea level(alt)
• time
• deadtime_correction_counts
• background_signal_std_co_pol
• range_bin_time
• deadtime_correction
• range_bins
• energy_monitor
• range_offset
• Preliminary cloud base height(preliminary_cbh)
• scope_temp

SGP/MPL/C1 - Laser and power supply failure

Missing and incorrect data due to MPL laser and power supply failure.

• num_channels
• background_signal_co_pol
• range
• num_bins
• dead_time_corrected
• pulse_rep
• background_signal_std_cross_pol
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• laser_temp
• first_data_bin
• background_signal_cross_pol
• overlap_correction
• detector_temp
• max_altitude
• range_bin_width
• Attenuated backscatter, copol(signal_return_co_pol)
• overlap_correction_heights
• mcs_mode
• polarization_control_voltage
• polarization_control
• deadtime_correction_counts
• background_signal_std_co_pol
• range_bin_time
• deadtime_correction
• range_bins
• energy_monitor
• range_offset
• Preliminary cloud base height(preliminary_cbh)
• scope_temp

SGP Site Power Outage Due to Winter Storm

On Saturday and Sunday, December 26 and 27th a powerful winter storm (Goliath) brought 
sleet and freezing rain to much of Oklahoma with wind gusts of 45 MPH at times. The result 
was very very slick roads and mass power outages.
 
The SGP central facility lost power at 8:55 PM CDT on Sunday, December 27th.  
The power was restored on 7:56 PM CDT on Wednesday, December 30th
 
Site Emergency procedures were activated and Technicians drained water out of instrument 
reservoirs and other measures as needed, early Monday morning.
 
On Wednesdays as roads and power started was restored to much of the areas east of I-35 , 
Site Technicians performed maintenance on several Extended Facilities.

During this period, data are potentially missing, incorrect, or suspect.  Carefully 
inspect the data before use.

• range_offset
• laser_scalar_sync_offset
• energy_monitor
• transceiver_altitude_angle
• laser_sync_offset
• laser_temp
• instrument_temp
• range
• shots_sum
• voltage_05
• range_bins
• shots_summed
• deadtime_correction
• property
• range_bin_width
• East longitude(lon)
• Pressure, associated geometric height, at altitude, NGM model output(height)
• Preliminary cloud base height(preliminary_cbh)
• filter_temp
• trigger_freq
• time
• voltage_15
• voltage_10
• pulse_rep
• Backscatter, ceilometer, range and sensitivity corrected(backscatter)
• range_bin_time
• time_offset
• base_time
• scalar_sync_offset
• total_counts
• background_signal
• North latitude(lat)
• detector_counts
• max_altitude
• detector_temp
• assumed_zero_range_bin
• Altitude above mean sea level(alt)
• transceiver_azimuth_angle

• num_channels
• qc_signal_return_co_pol
• num_bins
• qc_signal_return_cross_pol
• first_data_bin
• East longitude(lon)
• time_offset
• deadtime_correction_counts
• Preliminary cloud base height(preliminary_cbh)
• Pressure, associated geometric height, at altitude, NGM model output(height)
• qc_scope_temp
• base_time
• max_altitude
• range_bin_width
• overlap_correction_heights
• qc_range_offset
• polarization_control_voltage
• deadtime_correction
• background_signal_std_co_pol
• range_offset
• scope_temp
• North latitude(lat)
• background_signal_co_pol
• range
• qc_time
• pulse_rep
• background_signal_std_cross_pol
• qc_energy_monitor
• qc_preliminary_cbh
• Altitude above mean sea level(alt)
• time
• range_bin_time
• range_bins
• qc_laser_temp
• dead_time_corrected
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• laser_temp
• background_signal_cross_pol
• overlap_correction
• detector_temp
• Attenuated backscatter, copol(signal_return_co_pol)
• mcs_mode
• polarization_control
• qc_detector_temp
• energy_monitor

• time_offset
• range_bin_time
• East longitude(lon)
• energy_monitor
• Pressure, associated geometric height, at altitude, NGM model output(height)
• range
• pulse_rep
• background_signal_std
• range_offset
• Altitude above mean sea level(alt)
• shots_per_avg
• signal_return
• laser_temp
• max_altitude
• scope_temp
• Preliminary cloud base height(preliminary_cbh)
• time
• detector_temp
• North latitude(lat)
• num_bins
• background_signal
• range_bin_width
• range_bins
• num_channels
• dead_time_corrected
• polarization_control_voltage
• base_time
• polarization_control

Continuing signal degradation

Despite recent efforts (970310-970314) by the instrument mentor, signal 
degradation of the MPL has continued.  The degradation has continued to the 
point that the effective range of the MPL is nearing 10 km.  The instrument mentor and PI 
have 
concluded that an overhaul of the instrument by the vendor is in order.

• North latitude(lat)
• East longitude(lon)
• Pressure, associated geometric height, at altitude, NGM model output(height)
• range_offset
• range
• shots_sum
• laser_scalar_sync_offset
• Preliminary cloud base height(preliminary_cbh)
• filter_temp
• voltage_05
• trigger_freq
• time
• max_altitude
• range_bins
• energy_monitor
• detector_temp
• transceiver_altitude_angle
• shots_summed
• deadtime_correction
• voltage_15
• Altitude above mean sea level(alt)
• property
• voltage_10
• range_bin_width
• pulse_rep
• Backscatter, ceilometer, range and sensitivity corrected(backscatter)
• laser_sync_offset
• range_bin_time
• laser_temp
• time_offset
• base_time
• scalar_sync_offset
• instrument_temp
• total_counts
• background_signal
• transceiver_azimuth_angle

SGP/MPL - Missing data due to blown detector

Sometime early 11/11 the detector on the
MPL-004 blew out.  The Detector was replaced by Albert Mendoza.
The instrument was operational on Jan. 23, 1999.

Link this to P981119.2 that reported the blown detector and the
corrective action taken

• North latitude(lat)
• East longitude(lon)
• Pressure, associated geometric height, at altitude, NGM model output(height)
• range_offset
• range
• shots_sum
• laser_scalar_sync_offset
• Preliminary cloud base height(preliminary_cbh)
• filter_temp
• voltage_05
• trigger_freq
• time
• max_altitude
• range_bins
• energy_monitor
• detector_temp
• transceiver_altitude_angle
• shots_summed
• deadtime_correction
• voltage_15
• Altitude above mean sea level(alt)
• property
• voltage_10
• range_bin_width
• pulse_rep
• Backscatter, ceilometer, range and sensitivity corrected(backscatter)
• laser_sync_offset
• range_bin_time
• laser_temp
• time_offset
• base_time
• scalar_sync_offset
• instrument_temp
• total_counts
• background_signal
• transceiver_azimuth_angle