Culebra Aerosol Research Lidar Project, Description and First Results

JENS LAUTENBACH, Pedrina Terra, Josef Hoeffner, Arecibo Observatory - University of Central Florida

     Abstract Number: 293
     Working Group: Instrumentation and Methods

Abstract
This presentation outlines an instrumental description of the Culebra Aerosol Research Lidar (CARLA) and presents the first results from the CARLA Project. CARLA was developed at the main site of the Arecibo Observatory, Puerto Rico and is undergoing operation tests before it is deployed at the Remote Optica Facility of the Arecibo Observatory in Culebra Island. It provides the scientific community with data on aerosol vertical distribution over time at a Caribbean location. This includes Dust coming across the Atlantic Ocean from the African continent. African Dust plays an essential role in the Caribbean lower atmosphere because it influences hurricane formation, weather, and the health of our population, among others.

High Spectral Resolution Lidar (HSRL), like CARLA, can directly retrieve the aerosol backscatter and extinction. The HSR technique has the highest accuracy of all aerosol lidar (Mona et al., 2012). As described in Mona et al. 2012, p. 7: “this technique utilized the difference in the Doppler frequency shifts produced by photons scattered by molecules (random motion) and by particles (motion determined by wind and turbulence).”

CARLA uses a continuous wave tapered amplifier diode laser modulated with 4 kHz and cleaned up by a polarizing beam splitter to send out highly polarised laser pulses in the atmosphere. The backscattered signal from the atmosphere is then directed to the three-channel receiver unit by a 40 cm telescope with a FOV of 100 μrad. The first channel uses a 10 nm Bandpass filter to receive the backscattered Rayleigh (molecules) signal. An Etalon is installed in the second and third channel as HSR filter, followed by a 10 nm Bandpass filter to retrieve the Mie (particles) backscattered signal. The two HSR-channels are laid out to measure both polarisation components of the Mie signal. By applying this technique, CARLA measures molecular (Rayleigh) scattering and particle (Mie) scattering with both polarisations to determine solid particles and liquid droplets in the atmosphere.

Apart from the scientific objectives, this project aims to increase opportunities for the educational system through outreach activities for Puerto Rico’s K-12 schools and university students to perform hands-on research experiences. Some students have already benefitted from this opportunity.