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Studying the Physical Properties of the Atmosphere using LIDAR technique Dinh Van Trung and Nguyen Thanh Binh, Nguyen Dai Hung, Dao Duy Thang, Bui Van Hai, Nguyen Xuan Tuan Institute of Physics, Vietnam Academy of Science and Technology. Metal layers (Na, K, Fe ...). Cirrus clouds.

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slide1

Studying the Physical Properties of the Atmosphere using LIDAR technique

Dinh Van Trung

and

Nguyen Thanh Binh, Nguyen Dai Hung,

Dao Duy Thang, Bui Van Hai, Nguyen Xuan Tuan

Institute of Physics,

Vietnam Academy of Science and Technology

slide2

Metal layers (Na, K, Fe ...)

Cirrus clouds

Aerosols, clouds, gases

slide3

Monthly mean AOD in March 2006 by MODIS

at 550 nm and forward trajectories of air parcels

Deng et al. (2008)

slide4

Why do we develop LIDAR to study the atmosphere

- High spatial and temporal resolution

- Large measurement range

- Continuous coverage in time

slide5

High power pulsed laser and the transient recorder are usually the most expensive components of the LIDAR

Computer

slide7

Laser trasmmitter

f/D=10

20 cm

Option !

Spatial filter

Collimator

Raman channel

N2or H2O

Dichroic mirror

1064/532 nm

1064 nm filter

Nd:YAG

1064 nm

Photodiode trigger

532 nm filter

APD

PMT

Polarizing beam splitter

PMT

ADC

Photon counter #1

Photon counter #1

PMT

Photodiode trigger

λ/2 wave-plate

ADC

Nd:YAG

532 nm

Computer

Photon counter #2

slide10

Main characteristics of the LIDAR system

Transmitter: Quantel Brilliant Nd:YAG laser (10 Hz, 350 mJ/pulse at 1064 nm, 180 mJ/pulse at 532 nm)

Receiving module:

- Telescope: 20 cm in diameter, f/D = 10

- Dichroic beam splitter: 1064 nm/532 nm

- Narrow band filters:

3 nm for 532 nm channel

10 nm for 1064 nm channel

- Detectors:

APD for 1064 nm channel

PMT in either analog or photon counting mode

for 532 nm channels

slide11

Detectors

- 1064 nm channel:

Avalanche photodiode + Trans-impedance amplifier

- 532 nm channels: R7400U from Hamamatsu

- Raman channels (607 nm or 660 nm):

H6780-20 photosensor module from Hamamatsu

Digitizer for analog detection

- Up to 03 simultaneous channels

- Shielded & low noise pre-amplifier

- 12-bit ADC at 20 MSPS (80 MSPS possible)

slide12

Development of photon counting technique

High speed amplifier

Discriminator

PMT

HV PS

Pulse stretcher

FPGA board

with USB

Computer

High speed USB Scope

Our electronic detection system provides flexible and low cost multichannel photon counting capability.

slide13

LIDAR signal measured with Photon counting technique

1-minute average (600 shots)

Single shot after the amplifier and pulse stretcher

slide16

532 nm channel (18 April 2011) analog mode,

30-minute average at 10:30 am and at 11:30 am

MSIS-90E model for Hanoi

Time (μsec)

slide17

Elastic & N2 Raman measurements

Raman N2 607 nm

532 nm

00:30 to 03:30 am, 18 October 2010

slide19

Elastic & H2O Raman measurements

532 nm

H2O Raman at 660 nm

slide21

Depolarization measurement at 532 nm

(18 May 2011) 10-minute average at 10:00 am

slide23

532 nm channel in photon counting mode

18 April 2011, 20-minute average

MSIS-90E model for Hanoi

slide26

Boundary layer monitoring with LIDAR

Small (8-cm) telescope for 532 nm

channel

slide28

Small LIDAR for boundary layer monitoring

Transmitter:

Pulsed diode laser at 905 nm

Repetition rate 5 kHz

Pulse width 100 ns

Pulse energy 1 - 2 μJ

Receiving module:

Telescope 20 cm in diameter

Bandpass filter 10 nm FWHM

Cooled APD in Geiger photon counting mode

slide30

Backscattered signal from clouds

Backscattered signal from atmosphere

slide31

Summary

- Atmospheric properties and different solid and gaseous components have been probed using a dual wavelength LIDAR was developed at IoP.

- Aerosol distribution above Hanoi is being measured and found to be distributed mostly below about 4 - 5 km.

- Cirrus clouds have been monitored regularly.

- The LIDAR is being been used regularly to monitor the boundary layer.

- Atmospheric temperature profile up to above 30 km has been measured with satisfactory accuracy.