TWP/VCEIL/C1 - Ceilometer offset

When the replacement ceilometer was installed at Manus it was tilted 6 degrees.
Since the angle correction setting was not activated, the cloud base heights
reported by the instrument were higher than actual by 0.55% (39 m at 7 km).

• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Third cloud base height(third_cbh)

TWP/VCEIL/C1 - Ceilometer clock drift

During this period the ceilometer was using a software version that
provided time stamps that were based on the ceilometer clock and
not the computer clock that was continually sychronized with GPS.
This lead to times that were erroneous by as much as 2 minutes. For
most applications 2 minutes is an acceptable error, but for some
applications this may be a problem.

• Laser temperature(laser_temperature)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• lon(lon)
• Backscatter sum(sum_backscatter)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• base time(base_time)
• Altitude of highest signal(alt_highest_signal)
• Vertical visibility(vertical_visibility)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• Degrees from vertical (0 to +90)(tilt_angle)
• Dummy altitude for Zeb(alt)
• lat(lat)
• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Third cloud base height(third_cbh)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• range(range)
• GPS raw data filename(filename)
• Warning and alarm status bits(status_string)
• Detection status. See details(detection_status)
• Time offset of tweaks from base_time(time_offset)
• Millivolts at internal ADC input (0 to 2500)(background_light)

• Lowest cloud base height detected.(first_cbh)
• Dummy altitude for Zeb(alt)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Second lowest cloud base height(second_cbh)
• Altitude of highest signal(alt_highest_signal)
• Time offset of tweaks from base_time(time_offset)
• Degrees from vertical (0 to +90)(tilt_angle)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• GPS raw data filename(filename)
• Vertical visibility(vertical_visibility)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Warning and alarm status bits(status_string)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Backscatter sum(sum_backscatter)
• lon(lon)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• Detection status. See details(detection_status)
• range(range)
• Laser temperature(laser_temperature)
• lat(lat)
• Third cloud base height(third_cbh)
• base time(base_time)

• null(Raw data stream - documentation not supported)

TWP/VCEIL/C1 - Extended data gap

There is no ceilometer data for this period.

• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Laser temperature(laser_temperature)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• lon(lon)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Third cloud base height(third_cbh)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Backscatter sum(sum_backscatter)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• base time(base_time)
• GPS raw data filename(filename)
• range(range)
• Vertical visibility(vertical_visibility)
• Altitude of highest signal(alt_highest_signal)
• Warning and alarm status bits(status_string)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• Degrees from vertical (0 to +90)(tilt_angle)
• Dummy altitude for Zeb(alt)
• Detection status. See details(detection_status)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Time offset of tweaks from base_time(time_offset)
• lat(lat)

• Backscatter sum(sum_backscatter)
• Lowest cloud base height detected.(first_cbh)
• lon(lon)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Dummy altitude for Zeb(alt)
• Second lowest cloud base height(second_cbh)
• Altitude of highest signal(alt_highest_signal)
• Time offset of tweaks from base_time(time_offset)
• Detection status. See details(detection_status)
• Degrees from vertical (0 to +90)(tilt_angle)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Vertical visibility(vertical_visibility)
• GPS raw data filename(filename)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• range(range)
• Laser temperature(laser_temperature)
• lat(lat)
• Warning and alarm status bits(status_string)
• Third cloud base height(third_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• base time(base_time)
• Aerosol backscatter coefficient at 355 nm(backscatter)

TWP/VCEIL/C1 - Extended data gap

There is no ceilometer data for this period.

• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Laser temperature(laser_temperature)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• lon(lon)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Third cloud base height(third_cbh)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Backscatter sum(sum_backscatter)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• base time(base_time)
• GPS raw data filename(filename)
• range(range)
• Vertical visibility(vertical_visibility)
• Altitude of highest signal(alt_highest_signal)
• Warning and alarm status bits(status_string)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• Degrees from vertical (0 to +90)(tilt_angle)
• Dummy altitude for Zeb(alt)
• Detection status. See details(detection_status)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Time offset of tweaks from base_time(time_offset)
• lat(lat)

• Backscatter sum(sum_backscatter)
• Lowest cloud base height detected.(first_cbh)
• lon(lon)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Dummy altitude for Zeb(alt)
• Second lowest cloud base height(second_cbh)
• Altitude of highest signal(alt_highest_signal)
• Time offset of tweaks from base_time(time_offset)
• Detection status. See details(detection_status)
• Degrees from vertical (0 to +90)(tilt_angle)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Vertical visibility(vertical_visibility)
• GPS raw data filename(filename)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• range(range)
• Laser temperature(laser_temperature)
• lat(lat)
• Warning and alarm status bits(status_string)
• Third cloud base height(third_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• base time(base_time)
• Aerosol backscatter coefficient at 355 nm(backscatter)

TWP/VCEIL/C1 - Extended data gap

There is no ceilometer data for this period.

• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Laser temperature(laser_temperature)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• lon(lon)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Third cloud base height(third_cbh)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Backscatter sum(sum_backscatter)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• base time(base_time)
• GPS raw data filename(filename)
• range(range)
• Vertical visibility(vertical_visibility)
• Altitude of highest signal(alt_highest_signal)
• Warning and alarm status bits(status_string)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• Degrees from vertical (0 to +90)(tilt_angle)
• Dummy altitude for Zeb(alt)
• Detection status. See details(detection_status)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Time offset of tweaks from base_time(time_offset)
• lat(lat)

• Backscatter sum(sum_backscatter)
• Lowest cloud base height detected.(first_cbh)
• lon(lon)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Dummy altitude for Zeb(alt)
• Second lowest cloud base height(second_cbh)
• Altitude of highest signal(alt_highest_signal)
• Time offset of tweaks from base_time(time_offset)
• Detection status. See details(detection_status)
• Degrees from vertical (0 to +90)(tilt_angle)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Vertical visibility(vertical_visibility)
• GPS raw data filename(filename)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• range(range)
• Laser temperature(laser_temperature)
• lat(lat)
• Warning and alarm status bits(status_string)
• Third cloud base height(third_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• base time(base_time)
• Aerosol backscatter coefficient at 355 nm(backscatter)

TWP/VCEIL/C1 - Degraded Ceilometer Window

Data from the ceilometer during this period is suspect. From 10/28
until about 2/4 the instrument had a deteriorated window.  This
caused the ceilometer to only be able to see cloud heights up to
about 2 km.

• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)

• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Third cloud base height(third_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)

TWP/VCEIL/C1 - Receiver Problem

The Manus ceilometer had degraded cloud base height due to a receiver problem

• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)

• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Third cloud base height(third_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)

TWP/VCEIL/C1 - Manus Ceilometer Laser Power Intermittent

Very few cloud heights reported due to bad laser transmitter.

Replaced ceilometer 05:00 GMT 18 Jan. 2002.

• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)

• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Third cloud base height(third_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)

TWP/VCEIL/C1 - Reprocess: Incorrect units on installed ceilometer

The units setting on the ceilometer installed on 18 Jan. 2002 were incorrectly set to feet 
rather than meters.

• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)

• Second lowest cloud base height(second_cbh)
• Lowest cloud base height detected.(first_cbh)
• Third cloud base height(third_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)

TWP/VCEIL/C2 - Installation

The Nauru ARCS was installed during the period September-November
1998.  Data were being collected by the end of October, but for the
first several weeks of November, the site was undergoing considerable
change, so data from that period should be used with caution.  The
official site dedication occured on November 20.  Most on-site
activity ended following the dedication so we will consider November
20 to be the beginning of the Nauru operations.  The last members of
the installation team left Nauru on November 24.

• Backscatter sum(sum_backscatter)
• Degrees from vertical (0 to +90)(tilt_angle)
• lon(lon)
• Vertical visibility(vertical_visibility)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Time offset of tweaks from base_time(time_offset)
• Warning and alarm status bits(status_string)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Altitude of highest signal(alt_highest_signal)
• GPS raw data filename(filename)
• range(range)
• Dummy altitude for Zeb(alt)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• base time(base_time)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Detection status. See details(detection_status)
• Laser temperature(laser_temperature)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Flag indicating aeri retrieval status(status_flag)
• Lowest cloud base height detected.(first_cbh)
• Millivolts at internal ADC input(window_contamination)
• lat(lat)

• null(Raw data stream - documentation not supported)

• lat(lat)
• Backscatter sum(sum_backscatter)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• base time(base_time)
• Degrees from vertical (0 to +90)(tilt_angle)
• Altitude of highest signal(alt_highest_signal)
• Detection status. See details(detection_status)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• GPS raw data filename(filename)
• lon(lon)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• range(range)
• Third cloud base height(third_cbh)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Laser temperature(laser_temperature)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Dummy altitude for Zeb(alt)
• Lowest cloud base height detected.(first_cbh)
• Warning and alarm status bits(status_string)
• Vertical visibility(vertical_visibility)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Second lowest cloud base height(second_cbh)
• Time offset of tweaks from base_time(time_offset)

TWP/C1 - Incorrect elevation reported in Manus Data

Bill Clements reports we have been using 6m MSL as the station elevation of Momote 
(Manus).  This was based on information posted near the station barometer in the Momote Weather 
Service Office.  It turns out that the official WMO station elevation for Momote is 4m 
MSL and the upper air elevation is 5m MSL.

All Manus instruments except the sonde station are at 4m MSL. The sonde launching station 
is at 5m MSL.

• Dummy altitude for Zeb(alt)

• Dummy altitude for Zeb(alt)

• Dummy altitude for Zeb(alt)

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.

• Warning and alarm status bits(status_string)
• Backscatter sum(sum_backscatter)
• Altitude of highest signal(alt_highest_signal)
• Vertical visibility(vertical_visibility)
• range(range)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Flag indicating aeri retrieval status(status_flag)
• Lowest cloud base height detected.(first_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)

• Altitude of highest signal(alt_highest_signal)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• range(range)
• Backscatter sum(sum_backscatter)
• Warning and alarm status bits(status_string)
• Vertical visibility(vertical_visibility)
• Detection status. See details(detection_status)
• Third cloud base height(third_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Second lowest cloud base height(second_cbh)
• Flag indicating aeri retrieval status(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(lon)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Dummy altitude for Zeb(alt)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• base time(base_time)
• Detection status. See details(detection_status)
• Warning and alarm status bits(status_string)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Altitude of highest signal(alt_highest_signal)
• GPS raw data filename(filename)
• Laser temperature(laser_temperature)
• range(range)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Flag indicating aeri retrieval status(status_flag)
• Lowest cloud base height detected.(first_cbh)
• lat(lat)

• null(Raw data stream - documentation not supported)

• lat(lat)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• lon(lon)
• range(range)
• Backscatter sum(sum_backscatter)
• Third cloud base height(third_cbh)
• base time(base_time)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Degrees from vertical (0 to +90)(tilt_angle)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Laser temperature(laser_temperature)
• Altitude of highest signal(alt_highest_signal)
• Dummy altitude for Zeb(alt)
• Lowest cloud base height detected.(first_cbh)
• Warning and alarm status bits(status_string)
• Vertical visibility(vertical_visibility)
• Detection status. See details(detection_status)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Second lowest cloud base height(second_cbh)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• Time offset of tweaks from base_time(time_offset)
• GPS raw data filename(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

• Backscatter sum(sum_backscatter)
• Lowest cloud base height detected.(first_cbh)
• lon(lon)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• Dummy altitude for Zeb(alt)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Second lowest cloud base height(second_cbh)
• Altitude of highest signal(alt_highest_signal)
• Time offset of tweaks from base_time(time_offset)
• Degrees from vertical (0 to +90)(tilt_angle)
• Detection status. See details(detection_status)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• GPS raw data filename(filename)
• Vertical visibility(vertical_visibility)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• range(range)
• Laser temperature(laser_temperature)
• lat(lat)
• Warning and alarm status bits(status_string)
• Third cloud base height(third_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• base time(base_time)
• Millivolts at internal ADC input (0 to 2500)(background_light)

• null(Raw data stream - documentation not supported)

TWP/VCEIL/C2 - Ceilometer failure

Large data gaps began occurring frequently at the TWP Nauru site 26 February at 06Z.  
Prior to 25 February, optical cross talk errors had been observed.  Beginning on 25 February, 
data errors were observed.  By 26 February, these errors were exhibiting themselves as 
extended data gaps.  These gaps became increasingly frequent between 2/26 and 3/4.  All 
data are missing after 20050304.1550.

The instrument was replaced on 29 March and after some subsequent configuration work, the 
instrument was revived just after 00Z on 1 April.

• Backscatter sum(sum_backscatter)
• Degrees from vertical (0 to +90)(tilt_angle)
• lon(lon)
• Vertical visibility(vertical_visibility)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Dummy altitude for Zeb(alt)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• base time(base_time)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Time offset of tweaks from base_time(time_offset)
• Warning and alarm status bits(status_string)
• Detection status. See details(detection_status)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Altitude of highest signal(alt_highest_signal)
• GPS raw data filename(filename)
• Laser temperature(laser_temperature)
• range(range)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Flag indicating aeri retrieval status(status_flag)
• Lowest cloud base height detected.(first_cbh)
• Millivolts at internal ADC input(window_contamination)
• lat(lat)

• null(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.

• Detection status. See details(detection_status)
• Warning and alarm status bits(status_string)
• Backscatter sum(sum_backscatter)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Altitude of highest signal(alt_highest_signal)
• Degrees from vertical (0 to +90)(tilt_angle)
• GPS raw data filename(filename)
• Laser temperature(laser_temperature)
• Vertical visibility(vertical_visibility)
• lon(lon)
• range(range)
• Third cloud base height(third_cbh)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Second lowest cloud base height(second_cbh)
• Flag indicating aeri retrieval status(status_flag)
• Dummy altitude for Zeb(alt)
• Lowest cloud base height detected.(first_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Millivolts at internal ADC input(window_contamination)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• base time(base_time)
• lat(lat)
• Time offset of tweaks from base_time(time_offset)

TWP/VCEIL/C2 - Vceil computer disconnected

VCEIL computer was disconnected during this time period.

• Detection status. See details(detection_status)
• Warning and alarm status bits(status_string)
• Backscatter sum(sum_backscatter)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Altitude of highest signal(alt_highest_signal)
• Degrees from vertical (0 to +90)(tilt_angle)
• GPS raw data filename(filename)
• Laser temperature(laser_temperature)
• Vertical visibility(vertical_visibility)
• range(range)
• Third cloud base height(third_cbh)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Second lowest cloud base height(second_cbh)
• Flag indicating aeri retrieval status(status_flag)
• Lowest cloud base height detected.(first_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Millivolts at internal ADC input(window_contamination)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• base time(base_time)
• Time offset of tweaks from base_time(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.

• Warning and alarm status bits(status_string)
• Detection status. See details(detection_status)
• Backscatter sum(sum_backscatter)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Altitude of highest signal(alt_highest_signal)
• Degrees from vertical (0 to +90)(tilt_angle)
• Laser temperature(laser_temperature)
• Vertical visibility(vertical_visibility)
• range(range)
• Third cloud base height(third_cbh)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Second lowest cloud base height(second_cbh)
• Flag indicating aeri retrieval status(status_flag)
• Lowest cloud base height detected.(first_cbh)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Millivolts at internal ADC input(window_contamination)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• base time(base_time)
• Time offset of tweaks from base_time(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)
• Altitude of highest signal(alt_highest_signal)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Millivolts at internal ADC input(window_contamination)
• Vertical visibility(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.

• Backscatter sum(sum_backscatter)
• Second lowest cloud base height(second_cbh)
• Altitude of highest signal(alt_highest_signal)
• Lowest cloud base height detected.(first_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• Vertical visibility(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)
• Altitude of highest signal(alt_highest_signal)
• Backscatter sum(sum_backscatter)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Lowest cloud base height detected.(first_cbh)
• Vertical visibility(vertical_visibility)
• Third cloud base height(third_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Aerosol backscatter coefficient at 355 nm(backscatter)

Calibration interruption at TWP Nauru

The ceilometer was tipped horizontal for a calibration check

• Backscatter sum(sum_backscatter)
• Degrees from vertical (0 to +90)(tilt_angle)
• lon(lon)
• Vertical visibility(vertical_visibility)
• Third cloud base height(third_cbh)
• Second lowest cloud base height(second_cbh)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Time offset of tweaks from base_time(time_offset)
• Warning and alarm status bits(status_string)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Altitude of highest signal(alt_highest_signal)
• GPS raw data filename(filename)
• range(range)
• Dummy altitude for Zeb(alt)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• base time(base_time)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• Detection status. See details(detection_status)
• Laser temperature(laser_temperature)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Flag indicating aeri retrieval status(status_flag)
• Lowest cloud base height detected.(first_cbh)
• Millivolts at internal ADC input(window_contamination)
• lat(lat)

• null(Raw data stream - documentation not supported)

• lat(lat)
• Backscatter sum(sum_backscatter)
• Aerosol backscatter coefficient at 355 nm(backscatter)
• base time(base_time)
• Degrees from vertical (0 to +90)(tilt_angle)
• Altitude of highest signal(alt_highest_signal)
• Detection status. See details(detection_status)
• Flag indicating aeri retrieval status(status_flag)
• Millivolts at internal ADC input(window_contamination)
• GPS raw data filename(filename)
• lon(lon)
• Percentage of nominal factory setting (0 to 999%)(receiver_sensitivity)
• range(range)
• Third cloud base height(third_cbh)
• 6 character string describing instrument measurement parameters(measurement_parameters)
• Laser temperature(laser_temperature)
• Percentage of nominal factory setting (0 to 999%)(laser_pulse_energy)
• Dummy altitude for Zeb(alt)
• Lowest cloud base height detected.(first_cbh)
• Warning and alarm status bits(status_string)
• Vertical visibility(vertical_visibility)
• Millivolts at internal ADC input (0 to 2500)(background_light)
• Second lowest cloud base height(second_cbh)
• Time offset of tweaks from base_time(time_offset)