TWP/VCEIL/C2 - Nauru Vceil data suspect

During this period the ceilometer began producing a cross-talk warning. Since it is a 
warning, some of the data are OK. However, the instrument began to be limited to detecting 
clouds only about 2 km above the ground.

• status_string
• sum_backscatter
• alt_highest_signal
• vertical_visibility
• range
• Third cloud base height(third_cbh)
• status_flag
• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Backscatter(backscatter)
• receiver_sensitivity

• alt_highest_signal
• receiver_sensitivity
• range
• sum_backscatter
• status_string
• vertical_visibility
• detection_status
• Third cloud base height(third_cbh)
• Backscatter(backscatter)
• Second lowest cloud base height(second_cbh)
• status_flag

TWP/VCEIL/C2 - Power outage in I-Van resulted in Missing Data

I forgot to put in the daily report that we took the I van down yesterday to replace the 
fans in the Clary UPS. This was from 2300z on 24May03 to 0010z on 25May03. Instruments 
affected :

MPL
Ceilometer
MWR
WSI
TSI

Rex

• lon
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• alt
• background_light
• Backscatter(backscatter)
• receiver_sensitivity
• base_time
• status_string
• detection_status
• laser_pulse_energy
• alt_highest_signal
• filename
• laser_temperature
• range
• measurement_parameters
• status_flag
• Lowest cloud base height detected.(first_cbh)
• lat

• Raw data stream - documentation not supported

• lat
• lon
• receiver_sensitivity
• range
• sum_backscatter
• Third cloud base height(third_cbh)
• base_time
• Backscatter(backscatter)
• measurement_parameters
• tilt_angle
• laser_temperature
• laser_pulse_energy
• alt_highest_signal
• alt
• Lowest cloud base height detected.(first_cbh)
• status_string
• vertical_visibility
• detection_status
• background_light
• Second lowest cloud base height(second_cbh)
• status_flag
• window_contamination
• time_offset
• filename

TWP/VCEIL/C1 - Data dropouts

The Manus ceilometer was not receiving complete data packs from the ceilometer. This 
occurred at irregular intervals up to 3-10 times per hour until an error occurred and the 
computer locked up.  The data were not affected when they were successfully collected.  Days 
on which the data are missing for more than 1 hour are listed below.  Some maintenance 
was done on the ceilometer data computer in November and the computer was ultimately 
replace on 3 January 2005.

year.month.day
2004.09.29
2004.10.03
2004.10.04
2004.10.07
2004.10.10
2004.10.11
2004.10.12
2004.10.13
2004.10.14
2004.10.17
2004.10.18
2004.10.22
2004.10.25
2004.10.26
2004.10.27
2004.10.28
2004.10.29
2004.10.30
2004.11.15

• sum_backscatter
• Lowest cloud base height detected.(first_cbh)
• lon
• status_flag
• window_contamination
• laser_pulse_energy
• alt
• Second lowest cloud base height(second_cbh)
• alt_highest_signal
• time_offset
• detection_status
• tilt_angle
• receiver_sensitivity
• filename
• vertical_visibility
• measurement_parameters
• range
• laser_temperature
• lat
• status_string
• Third cloud base height(third_cbh)
• base_time
• background_light
• Backscatter(backscatter)

• Raw data stream - documentation not supported

TWP/VCEIL/C2 - occasional communication fault

Beginning August 30, 2005, the Nauru Ceilometer periodically went into a strange 
operational mode where the backscatter data exhibits vertical stripes.  Looking at the backscatter 
data - there are high amplitude oscillations occuring in the backscatter as a function 
of time at a given height.  The phenomenon appears to be more common at night.  Dates 
include: 30 Aug, 31 Aug, 1 Sep, 9 Sep, 15 Sep, 20 Oct, 22 Oct, 8 Dec, and others.

The fiber optic link to the ceilometer was faulty and causing periodic data corruption. 
The problem was corrected when the fiber optic line was replaced with a hard wired RS232 
link.

• status_string
• detection_status
• sum_backscatter
• laser_pulse_energy
• tilt_angle
• alt_highest_signal
• filename
• laser_temperature
• vertical_visibility
• range
• lon
• Third cloud base height(third_cbh)
• measurement_parameters
• status_flag
• Second lowest cloud base height(second_cbh)
• alt
• Lowest cloud base height detected.(first_cbh)
• background_light
• Backscatter(backscatter)
• window_contamination
• receiver_sensitivity
• base_time
• lat
• time_offset

TWP/VCEIL/C2 - Time offset

On 7/14/2006, I found that the ceilometer time was 8m 36s slow, the PC time display (lower 
right taskbar) was frozen at "22:24", and AboutTime was not running. Corrected it on 
7/17 by running AboutTime so that 19:03:29 became 19:12:05. This also corrected the frozen 
display on the Windows98 taskbar. 

I am not sure of the start time of this problem but there were several other Windows 
related issues that had to be corrected on 5/14 with indications of inappropriate access via 
Remote Administrator on 5/13. I do not know if the time offset was a sudden or gradual 
change.

• status_string
• detection_status
• sum_backscatter
• laser_pulse_energy
• tilt_angle
• alt_highest_signal
• laser_temperature
• vertical_visibility
• range
• Third cloud base height(third_cbh)
• measurement_parameters
• Second lowest cloud base height(second_cbh)
• status_flag
• Lowest cloud base height detected.(first_cbh)
• background_light
• Backscatter(backscatter)
• window_contamination
• base_time
• receiver_sensitivity
• time_offset

TWP/VCEIL/C2 - optical cross-talk compensation

The ceilometer gave frequent optical cross-talk compensation warnings, was insensitive to 
high clouds, and the tropics window was deteriorated. The instrument was replaced with a 
spare.

• Second lowest cloud base height(second_cbh)
• alt_highest_signal
• Backscatter(backscatter)
• window_contamination
• vertical_visibility
• Third cloud base height(third_cbh)

TWP/VCEIL/C2 - Receiver failure

The receiver failed and the instrument was replaced.  Data during the specified period are 
not valid.

• sum_backscatter
• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• alt_highest_signal
• Backscatter(backscatter)
• background_light
• vertical_visibility
• Third cloud base height(third_cbh)

TWP/VCEIL/C1 - Compensation fiber

The VCEIL was reporting a "receiver optical cross-talk compensation is poor" warning. The 
window was cleaned and the instrument was power-cycled. The problem was corrected when 
the compensation fiber was replaced and ants were removed from communication connector.  
Cloud detection was impaired.

• Second lowest cloud base height(second_cbh)
• alt_highest_signal
• sum_backscatter
• receiver_sensitivity
• laser_pulse_energy
• Lowest cloud base height detected.(first_cbh)
• vertical_visibility
• Third cloud base height(third_cbh)
• Backscatter(backscatter)
• background_light

TWP/VCEIL/C1 - Reprocess: Incorrect serial_number and sum_backscatter fields

Attribute serial_number: In most cases, this field is not representative of the actual 
serial number of the instrument because the value did not change when an instrument changed 
locations or was replaced with a spare.
   
Variable sum_backscatter: An out-of-range condition for the "sum of detected and 
normalized backscatter" was reported as 0 instead of missing (-9999). The valid range is 0 - 
0.0999 /srad.
   
This DQR also applies to a1 level data.

• sum_backscatter

TWP/VCEIL/C2 - Reprocess: Incorrect serial_number and sum_backscatter fields

Attribute serial_number: In most cases, this field is not representative of the actual 
serial number of the instrument because the value did not change when an instrument changed 
locations or was replaced with a spare.
   
Variable sum_backscatter: An out-of-range condition for the "sum of detected and 
normalized backscatter" was reported as 0 instead of missing (-9999). The valid range is 0 - 
0.0999 /srad.
   
This DQR also applies to a1 level data.

• sum_backscatter

TWP/VCEIL/C1 - Missing data

Data are missing and unrecoverable.

• Second lowest cloud base height(second_cbh)
• alt_highest_signal
• time_offset
• detection_status
• tilt_angle
• sum_backscatter
• Lowest cloud base height detected.(first_cbh)
• receiver_sensitivity
• lon
• status_flag
• filename
• vertical_visibility
• measurement_parameters
• range
• window_contamination
• laser_temperature
• lat
• laser_pulse_energy
• alt
• status_string
• Third cloud base height(third_cbh)
• base_time
• Backscatter(backscatter)
• background_light

TWP/VCEIL/C2 - Missing data

Data are missing and unrecoverable.

• detection_status
• status_string
• sum_backscatter
• laser_pulse_energy
• alt_highest_signal
• tilt_angle
• filename
• laser_temperature
• vertical_visibility
• lon
• range
• Third cloud base height(third_cbh)
• measurement_parameters
• Second lowest cloud base height(second_cbh)
• status_flag
• alt
• Lowest cloud base height detected.(first_cbh)
• Backscatter(backscatter)
• background_light
• window_contamination
• base_time
• receiver_sensitivity
• lat
• time_offset