DQR ID | Subject | Data Streams Affected | Data Quality Metric |
---|---|---|---|
D020227.8 | SGP/MPL/C1 - Data missing due to hardware failures | sgpmplC1.a1 | Missing |
D030922.3 | NSA/MPL/C1 - laser head failure | nsamplC1.a1 | Missing |
D040124.1 | NSA/MPL/C1 - Laser Q-Switch Problem | nsamplC1.a1 | Incorrect |
D040229.1 | NSA/MPL/C1 - Instrument problem | nsamplC1.a1 | Incorrect |
D040424.1 | SGP/MPL/C1 - Signal degrading | sgpmplC1.a1 | Suspect |
D040426.3 | NSA/MPL/C1 - Hardware Failure/Missing Data | nsamplC1.a1 | Missing |
D040426.4 | SGP/MPL/C1 - Detector Failure | sgpmplC1.a1 | Incorrect |
D040525.28 | SGP/MPL/C1 - Metadata errors | sgpmplC1.a1 | Does not affect quality |
D040706.4 | SGP/MPL/C1 - Reduced detection sensitivity | sgpmplC1.a1 | Suspect |
D050112.1 | NSA/C1 - Site-wide power failure | nsamplC1.a1 | Missing |
D050215.2 | NSA/MPL/C1 - Frost on Viewport Window | nsamplC1.a1 | Does not affect quality |
D050215.5 | NSA/MPL/C1 - MPL clock drift | nsamplC1.a1 | Suspect |
D050421.14 | SGP/MPL/C1 - Sensor Calibration | sgpmplC1.a1 | Incorrect |
D050608.1 | NSA/MPL/C1 - Diode failure | nsamplC1.a1 | Incorrect |
D050914.3 | SGP/MPL/C1 - Instrument offline | sgpmplC1.a1 | Missing |
D060327.2 | SGP/MPL/C1 - Intermittent Double Pulse from MPL laser | sgpmplC1.a1 | Does not affect quality |
D060327.3 | NSA/MPL/C1 - Intermittent Double Pulse from MPL laser | nsamplC1.a1 | Does not affect quality |
D970408.3 | Continuing signal degradation | sgpmplC1.a1 | Suspect |
D990224.1 | SGP/MPL - Missing data due to blown detector | sgpmplC1.a1 | Missing |
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
08/10/2001 | 0000 | 10/29/2001 | 2033 | Missing |
Subject: | SGP/MPL/C1 - Data missing due to hardware failures |
DataStreams: | sgpmplC1.a1 |
Description: | The MPL instrument was out of service during the time range specified due to hardware failures. Data during this period are missing and unrecoverable. |
Measurements: | sgpmplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
04/28/2002 | 0200 | 08/29/2002 | 0100 | Missing |
Subject: | NSA/MPL/C1 - laser head failure |
DataStreams: | nsamplC1.a1 |
Description: | On 2002-04-28 the laser energy was observed to decrease throughout the day. Although low clouds continued to be detected, by the end of the day the output laser energy was about 10% of nomimal. This decrease continued throughout 2002-04-29 to the extent that clouds were no longer detected. The source of failure was eventually determined to be the laser head, requiring the MPL to be shipped for repair. The MPL was reinstalled on 2002-08-28 at about 01:00 UTC. MPL NSA data from 2002-04-29 through 2002-08-27 (inclusive) should not be used. |
Measurements: | nsamplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
01/19/2004 | 2252 | 01/24/2004 | 0016 | Incorrect |
Subject: | NSA/MPL/C1 - Laser Q-Switch Problem |
DataStreams: | nsamplC1.a1 |
Description: | At about 22:52 UTC on 2004/01/19, the NSA MPL appears to have suffered a temporary failure of the laser Q-Switch. This results in a complete loss of lidar data immediately thereafter. The problem was resolved (at least for the time being) by disconnecting and reconnecting the Q-Switch cable on 2004/01/24 at about 00:16 UTC. Data after this time appears good. |
Measurements: | nsamplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
02/18/2004 | 0830 | 02/24/2004 | 0830 | Incorrect |
Subject: | NSA/MPL/C1 - Instrument problem |
DataStreams: | nsamplC1.a1 |
Description: | On 2/18, the energy monitor on the MPL dropped from 11 microjoules per second to 2 microjoules per second. This severely affected data quality. This appears to be have been an intermittent cable problem for the laser Q-Switch. A new cable was provided and installed on 2-24. |
Measurements: | nsamplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
09/25/2002 | 0000 | 01/16/2003 | 2359 | Suspect |
Subject: | SGP/MPL/C1 - Signal degrading |
DataStreams: | sgpmplC1.a1 |
Description: | 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. |
Measurements: | sgpmplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
11/21/2003 | 0500 | 12/01/2003 | 1441 | Missing |
Subject: | NSA/MPL/C1 - Hardware Failure/Missing Data |
DataStreams: | nsamplC1.a1 |
Description: | Data are missing during this extended period due to a hardware failure. |
Measurements: | nsamplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
01/16/2003 | 0000 | 01/31/2003 | 2359 | Incorrect |
Subject: | SGP/MPL/C1 - Detector Failure |
DataStreams: | sgpmplC1.a1 |
Description: | The detector failed following a period of data quality degradation. The MPL was replaced on 1/31/2003. |
Measurements: | sgpmplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
05/01/1996 | 0000 | 01/19/2000 | 2359 | Does not affect quality |
Subject: | SGP/MPL/C1 - Metadata errors |
DataStreams: | sgpmplC1.a1 |
Description: | 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 |
Measurements: | sgpmplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
07/01/2004 | 1500 | 07/07/2004 | 0350 | Suspect |
07/23/2004 | 2200 | 09/10/2004 | 2100 | Suspect |
Subject: | SGP/MPL/C1 - Reduced detection sensitivity |
DataStreams: | sgpmplC1.a1 |
Description: | 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. |
Measurements: | sgpmplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
12/13/2004 | 1000 | 12/13/2004 | 2330 | Missing |
Subject: | NSA/C1 - Site-wide power failure |
DataStreams: | nsamplC1.a1 |
Description: | The Barrow facility experienced a site-wide power failure on 12/13. Power was restored to most instruments between 2250 and 2330 GMT. |
Measurements: | nsamplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
05/21/1998 | 0000 | 09/25/2006 | 2159 | Does not affect quality |
Subject: | NSA/MPL/C1 - Frost on Viewport Window |
DataStreams: | nsamplC1.a1 |
Description: | During periods of extremely cold outside temperatures (-30 C or below), the MPL may suffer from reduced sensitivity due to obscuration of its viewport window with frost or condensation. During the winter of 1998-1999, on-site observers noted frost or condensation obscuring part or all of the viewport window. A fan providing blowing heated air on the viewport had failed. Although replacement of this fan reduced the degree of obscuration, the problem was not entirely eliminated. During the summer of 1999 a more robust forced-air system was installed and the problem was essentially solved except for during isolated cases of extremely cold weather. Under these extreme conditions partial or complete obscuration of the window is still possible with the result that cloud detection sensitivity will be reduced depending on the fraction of the window surface obscured. Even with significant obscuration, the MPL may still detect clouds and the cloud base heights of detected clouds will be reported correctly. This problem is one of detection sensitivity only and does not affect the range scale in any way. |
Measurements: | nsamplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
11/11/2003 | 0000 | 02/05/2004 | 0000 | Suspect |
Subject: | NSA/MPL/C1 - MPL clock drift |
DataStreams: | nsamplC1.a1 |
Description: | The MPL PC clock was noted to be off (slow) by more than an hour over a several day period. It has previously been noted that the time synchronization program "D-4" fails to update the PC clock under certain circumstances. As a result, the program "D-4" was replaced by "AboutTime" on 2/5/2004. The specifics of this problem are not well understood. It turns out that the instrument has TWO clocks on the instrument computer display - one being displayed by the MPL software and the other being the PC clock displayed in the lower right-hand corner of the screen. The MPL software clock was the one that is noted on daily rounds and was never off by any amount. Apparently the only clock that was off was the computer clock. What is clear is that between the time the MPL computer was installed on 11-11-2003 and the CM log on 1-06-2004 the MPL clock exhibited a discrepancy of over 1 hour and 20 minutes. What is not clear is whether this clock discrepancy was also applied to the data time stamps. Furthermore, seven days later the MPL clock exhibited only a 1.77 second drift. Not exceptional at all, and not in line with the previous discrepancy of more than 4800 seconds over a span of 57 days. Attempts to identify gradual correctible clock drift in the MPL data were not successful. As a worst-case scenario, the MPL data may be inappropriately time-stamped by as much a 1 hour 20 minutes and 41 seconds slow relative to UTC between the dates of 2003-11-11 and 2004-01-06. After this time until 2004-02-05 time synchronization was maintained within a few seconds a day with local observer assistance. |
Measurements: | nsamplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
11/03/2004 | 0000 | 02/23/2005 | 2300 | Incorrect |
Subject: | SGP/MPL/C1 - Sensor Calibration |
DataStreams: | sgpmplC1.a1 |
Description: | 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. |
Measurements: | sgpmplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
03/25/2005 | 1600 | 04/01/2005 | 2310 | Incorrect |
Subject: | NSA/MPL/C1 - Diode failure |
DataStreams: | nsamplC1.a1 |
Description: | On 3/25, the energy monitor on the MPL dropped from 11 microjoules per second to 2 microjoules per second. We determined the problem was the diode; it reached the end of its lifetime. A replacement was sent. Data quality returned to normal. |
Measurements: | nsamplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
07/07/2004 | 0350 | 07/23/2004 | 2150 | Missing |
Subject: | SGP/MPL/C1 - Instrument offline |
DataStreams: | sgpmplC1.a1 |
Description: | Instrument was taken offline due to a failure of the laser power supply. Data are missing and unrecoverable. |
Measurements: | sgpmplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
02/01/2005 | 0000 | 08/09/2006 | 1159 | Does not affect quality |
Subject: | SGP/MPL/C1 - Intermittent Double Pulse from MPL laser |
DataStreams: | sgpmplC1.a1 |
Description: | 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. |
Measurements: | sgpmplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
02/01/2005 | 0000 | 09/25/2006 | 2359 | Does not affect quality |
Subject: | NSA/MPL/C1 - Intermittent Double Pulse from MPL laser |
DataStreams: | nsamplC1.a1 |
Description: | 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. |
Measurements: | nsamplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
03/17/1997 | 0000 | 04/14/1997 | 2359 | Suspect |
Subject: | Continuing signal degradation |
DataStreams: | sgpmplC1.a1 |
Description: | 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. |
Measurements: | sgpmplC1.a1:
|
Start Date | Start Time | End Date | End Time | Data Quality Metric |
---|---|---|---|---|
11/11/1998 | 0000 | 01/23/1999 | 2359 | Missing |
Subject: | SGP/MPL - Missing data due to blown detector |
DataStreams: | sgpmplC1.a1 |
Description: | 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 |
Measurements: | sgpmplC1.a1:
|