The System of the Calibration for Visibility Measurement Instrument

The System of the Calibration for Visibility Measurement Instrument
EPJ Web of Conferences 1191,1 23005 (2016)
DOI: 10.1051/ epjconf/201611923005
ILRC 27
THE SYSTEM OF THE CALIBRATION FOR VISIBILITY
MEASUREMENT INSTRUMENT UNDER THE ATMOSPHERIC
AEROSOL SIMULATION ENVIRONMENT
Zhifeng Shu1,2* , ShaoChen Yang3 , Wenjing Xu3
1
Chinese Academy of Science, Key Laboratory of Geospace Environment, Hefei, Anhui, 230026,
China,*Email:szf@ustc.edu.cn
2
University of Science and Technology of China, School of Earth and Space Science, Hefei, Anhui,
230026, China
3. ShenZhen Darsunlaser Tech Co.,Ltd Shenzhen Guangdong,518067,China
ABSTRACT
Visibility is one of the most important parameters
for meteorological observation and numerical
weather prediction (NWP).It is also an important
factor in everyday life, mainly for surface and air
traffic especially in the Aeronautical Meteorology.
The visibility decides the taking off and landing of
aircraft. If the airport visibility is lower than
requirement for aircraft taking off stipulated by
International Civil Aviation Administration, then
the aircraft must be parked at the airport. So the
accurate measurement of visibility is very
important. Nowadays, many devices can be
measured the visibility or meteorological optical
range
(MOR)
such
as
Scatterometers,
Transmissometers and visibility lidar. But there is
not effective way to verify the accuracy of these
devices expect the artificial visual method. We
have developed a visibility testing system that can
be calibration and verification these devices. The
system consists of laser transmitter, optical
chopper, phase-locking amplifier, the moving
optic receiving system, signal detection and data
acquisition
system,
atmospheric
aerosol
simulation chamber. All of them were placed in
the atmosphere aerosol simulation chamber with
uniform aerosol concentration. The Continuous
wave laser, wavelength 550nm, has been
transmitted into the collimation system then the
laser beam expanded into 40mm diameter for
compressing the laser divergence angle before
modulated by optical chopper. The expanding
beam transmitting in the atmosphere aerosol cabin
received by the optic receiving system moving in
the 50m length precision guide with 100mm
optical aperture. The data of laser signal has been
acquired by phase-locking amplifier every 5 meter
range. So the 10 data points can be detected in the
50 meters guide once. The slope of the fitting
curve can be obtained by linear fitting these data
using the least square method. The laser extinction
coefficient was calculated from the slope using
the Koschmieder formula, then it been divided by
3 is MOR. The aerosol concentration in chamber
can be changed by adjusting aerosol generator that
producing variety of visibility atmospherical
environment. The experiment has been carried out
and the measurement accuracy of atmospheric
transmittance is 0.3‰ Corresponding to the
accuracy of MOR 4.9% at the 2km visibility
environment. So this system can be calibrated and
validated the other visibility measuring devices.
1. INTRODUCTION
Visibility is one of the most important parameters
for meteorological observation and numerical
weather prediction (NWP).It is also an important
factor in everyday life, mainly for surface and air
traffic
especially
in
the
Aeronautical
Meteorology[1,2,3]. Visibility is the most important
information for pilot of landing and taking off
aircraft. One of the most complicated phases of
flying an aircraft is landing approach. The ground
staff provide the pilot the visibility ( the runway
visual range RVR). The meteorological visual
range(MOR) is most important parameter for
composing the RVR. So the accurate
measurement of visibility is very important.
Nowadays, many devices can be measured the
visibility or meteorological optical range (MOR)
such as Scatterometers, Transmissometers and
visibility lidar. But there is not effective way to
verify the accuracy of these devices expect the
artificial visual method. We have developed a
visibility testing system that can be calibration
and verification these devices[4,5].
© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution
License 4.0 (http://creativecommons.org/licenses/by/4.0/).
EPJ Web of Conferences 1191,1 23005 (2016)
DOI: 10.1051/ epjconf/201611923005
ILRC 27
2. METHODOLOGY
Figure 1 shows that block diagrams of the
calibration system. The main container includes a
continuous wave (cw) laser with wave length
550nm and power 50mw, optical chopper with
frequency 20Hz to 1kHz , detector with model
thorlabs DET100A, motor control, phase-locking
amplifier , high precision guide and the optical
transceiver system. All of them are placed in the
atmosphere aerosol simulation environment with
LWH 65m╳2m╳2m. The Continuous wave laser,
wavelength 550nm, has been transmitted into the
collimation system then the laser beam expanded
into 40mm for compressing the laser divergence
angle before modulated by optical chopper. The
expanding beam transmitting in the atmosphere
aerosol cabin received by the optic receiving
system moving in the 50m length precision guide .
The data of laser signal has been acquired by
phase-locking amplifier every 5 meters range. So
the 10 data points can be detected in the 50 meters
guide once.
Fig2. Aerosol generation system
Fig1. The block diagrams of the visibility
calibration system
The
atmosphere
aerosol
simulation
environment is the transparent glass cabin the all
kinds of aerosol can be produced by the aerosol
generator such as atomizer aerosol generator,
atomizer aerosol generator, black carbon aerosol
generator. These generators are placed in a room
beside the glass cabin as shown in the figure 2.
The aerosol can be emitted in to the cabin through
the nine pipelines with uniform distribution along
the guide, then it will be mixed uniformly by the
10 convective fans distributed along the guide.
The aerosol concentration can be detected by the
concentration to ensure the uniform aerosol
distribution in the cabin. Figure 4 is the real
pictures and software interface of the system.
Fig3. The pictures of Atmospheric simulation
cabin
3. RESULTS
These system of visibility calibration have been
built in the tianjin province. In order to testing the
performance of the system a experiment has been
carried out. Laser beam has been emitted and been
chopped then the sigal will be detected by the
detector and data acquired by the phase-locking
amplifier that they are mounted on the cart. The
speed of the cart is 3m/s and it will stay 10
seconds when responsing the position sensor for
detecting and acquiring of the data. There will be
10 points data for calculating the MOR. There
data can be fitted linearly by the least square
method and the slope can be achieved. According
2
EPJ Web of Conferences 1191,1 23005 (2016)
DOI: 10.1051/ epjconf/201611923005
ILRC 27
to the lidar equation, the slope is the laser
atmosphere extinction coefficient, then it been
divided by 3 is MOR using Koschmieder formula.
Figure 4 is the laser energy change when the cart
goes and backs along the glass cabin. Fitting these
data the slope is -8.002-4 Corresponding to 3.6km
MOR using 3 divide the slope. The standard error
of the fitting is 3.11-5Corresponding to the of 4.9%
accuracy of MOR as shown in figure4.
[2] R.Boers, H.Klen baltink, H.J.Hemink,
F.C.Bosveld,M.Moerman,
Ground-based
observation and modeling of the visibility and
radar reflectivity in a radiation fog layer, Journal
of atmospheric and oceanic technology, Vol 30
288~299.
[3] M.A.Vanghan, D.M.Winker and K.A.Po-well.
“Part2: Feature detection and layer properties
algorithms” CALIOP Algorithm Theoretical Basis
Document PC-SCI-202 Part2, pp.87.
[4] Jurgen Streicher, Christian Werner. Design of a
small laser ceilometers and visibili-ty measuring
device for helicopter landi-ng sites[J]. Laser
Radar Technology for Remote Sensing, SPIE,
Vol.5240:31-41.
[5]. CHEN Min, SUN Dong-song, LI Hong-jing.
Detective method and analysis of atmosphere
slant visibility for lidar [J]. Infrared and Laser
Engineering, Vol 35(2): 156-160..
Fig4. The result of the experiment
4. CONCLUSIONS
The calibration system for visibility measurement
instrument under the aerosol simulation
environment has been built and the measuring
MOR expriment has been carried out and the
accuracy of MOR is 4.9% at 3.6km visibility. The
MOR accuracy of the Civil aviation
administration is ± 50m@MOR 10m~500m, ±
10%@MOR>500m~1500m, ± 20% @ MOR >
1500m~50000m.So this system can be used to
calibrate and validate the other visibility
measuring devices. There system is the first
visibility calibration device in the international
arena .It can be do some other meteorological
research under the atmosphere aerosol simulation
environment.
ACKNOWLEDGEMENT
This work was funded by the National Natural
Science Foundation of China (NSFC) project Nos.
41304123 and the civil aviation administration of
china.
REFERENCES
[1] J. Streicher, C.Monkel, H.Borchardt, Trial of
slant visual range measuring device, Journal of
atmospheric and oceanic technology, Vol 10
718~724,1993.
3
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