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...) Aerosols, clouds, gases Cirrus 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:YAG 1064 nm Photodiode trigger Nd:YAG 532 nm λ/2 wave-plate APD f/D=10 20 cm Collimator Spatial filter 1064 nm filter ADC 532 nm filter PMT Photon counter #1 Photon counter #2 Raman channel N2 or H2O PMT Photon counter #1 Computer Laser trasmmitter Polarizing beam splitter Dichroic mirror 1064/532 nm Photodiode trigger ADC Option !

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 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

Detectors nm channel: Avalanche photodiode + Trans-impedance amplifier nm channels: R7400U from Hamamatsu - Raman channels (607 nm or 660 nm): H 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 Discriminator 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 N nm Elastic & N 2 Raman measurements 00:30 to 03:30 am, 18 October 2010

Comparison between elastic and N 2 Raman signal

Elastic & H 2 O Raman measurements H 2 O Raman at 660 nm 532 nm

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

532 nm channel in photon counting mode 18 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 nm Repetition rate 5 kHz Pulse width 100 ns Pulse energy μJ Receiving module: Telescope 20 cm in diameter Bandpass filter 10 nm FWHM Cooled 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 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.