Studying the Physical Properties of the Atmosphere using LIDAR technique

Dinh Van Trungand

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 ...)

Aerosols, clouds, gasesCirrus clouds

Deng et al. (2008)

Monthly mean AOD in March 2006 by MODIS at 550 nm and forward trajectories of air parcels

Why do we develop LIDAR to study the atmosphere

- High spatial and temporal resolution

- Large measurement range

- Continuous coverage in time

Computer

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

Behrendt et al. (2002)

Nd:YAG1064 nm

Photodiode trigger

Nd:YAG532 nm

λ/2 wave-plate

APD

f/D=10

20 cm

Collimator

Spatial filter

1064 nm filter

ADC

532 nm filter

PM

T

PMT

Photon counter #1

Photon counter #2

Raman channel N2 or H2O

PM

T

Photon counter #1

Computer

Laser trasmmitter

Polarizing beam splitter

Dichroic mirror1064/532 nm

Photodiode trigger

ADC

Option !

Telescope

Laser Nd: YAG

1064 nm

532 nm

APD

DC power

PMT

Dichroic

λ/ 2

Fold mirror

Picoscope

Preamplifier

Initial version of the LIDAR in early 2010

Dual wavelength LIDAR system at IoP

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 channel10 nm for 1064 nm channel

- Detectors: APD for 1064 nm channelPMT in either analog or photon counting mode for 532 nm channels

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)

Development of photon counting technique

PMT

HV PS

High speed amplifier

High speed USB Scope

DiscriminatorDiscriminator

Pulse stretcher FPGA board with USB

Computer

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

LIDAR signal measured with Photon counting technique

Single shot after the amplifier and pulse stretcher

1-minute average (600 shots)

Labview GUI for data acquisition in analog or photon counting mode

1064 nm channel (13 April 2011) – 5-minute average

Time (μsec)

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

532 nm

Raman N2 607 nm

Elastic & N2 Raman measurements

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

Comparison between elastic and N2 Raman signal

Elastic & H2O Raman measurements

H2O Raman

at 660 nm532 nm

Depolarization measurement at 532 nm (18 May 2011) 10-minute average at 10:00 am

532 nm channel in photon counting mode18 April 2011, 20-minute average

MSIS-90E model for Hanoi

Temperature profile for 18 April 2011

LIDAR

Radiosonde

Boundary layer monitoring with LIDAR

Small (8-cm) telescope for 532 nm channel

Range corrected signal from 16:00 to 21:00 22 May 2011

Small LIDAR for boundary layer monitoring

Transmitter: Pulsed diode laser at 905 nmRepetition rate 5 kHzPulse width 100 nsPulse energy 1 - 2 μJ

Receiving module:Telescope 20 cm in diameterBandpass filter 10 nm FWHMCooled APD in Geiger photon counting mode

Small LIDAR system for boundary layer monitoring

Backscattered signal from atmosphere

Backscattered signal from clouds

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.