Joint elastic side-scattering LIDAR and Raman LIDAR measurements of aerosol optical properties in south east Colorado

Abstract

We describe an experiment, located in south-east Colorado, USA, that measured aerosol optical depth profiles using two L techniques. Two independent detectors measured scattered light from a vertical UV laser beam. One detector, located at the laser site, measured light via the inelastic Raman backscattering process. This is a common method used in atmospheric science for measuring aerosol optical depth profiles. The other detector, located approximately 40 km distant, viewed the laser beam from the side. This detector featured a 3.5 m 2 mirror and measured elastically scattered light in a bistatic L configuration following the method used at the Pierre Auger cosmic ray observatory. The goal of this experiment was to assess and improve methods to measure atmospheric clarity, specifically aerosol optical depth profiles, for cosmic ray UV fluorescence detectors that use the atmosphere as a giant calorimeter. The experiment collected data from September 2010 to July 2011 under varying conditions of aerosol loading. We describe the instruments and techniques and compare the aerosol optical depth profiles measured by the Raman and bistatic L detectors.

The Auger Raman Lidar: several years of continuous observations

“…Finally, the RL at Auger independently measures the vertical profiles of the aerosol optical properties, and it samples a column of the atmosphere located in the central part of Auger; considering this situation, the RL measurements of VAOD can be used as a cross-check for the other technique (namely the CLF method, see [2]) that estimate the aerosol attenuation in different regions of the observatory. A systematic comparison between these two techniques has been conducted in [3], not at Auger, but in a similar setup: there is a systematic small offset, on the other hand the two techniques were well correlated. A deeper analysis within Auger is in progress.…”

“…The data acquisition system uses analog (up to 80 MHz A/D) and Photon Counting (PhC, maximum count rate 250 MHz) acquisition modules. More technical details can be found in [3]. The RL is located in a temperature conditioned container (CLF).…”

Extraterrestrial Influences on Remote Sensing in the Earth’s Atmosphere

“…The changes in the atmospheric parameters and the precision of their determination are primarily connected with the solar radiation. They are recorded within all atmospheric layers, from the ionosphere and magnetosphere in the upper atmosphere [4][5][6] to the troposphere and stratosphere in the lower atmosphere [7]. The sources of these sudden perturbations can be the Sun, solar system, galaxy, or the wider Universe [3,8].…”

The Raman LIDAR for the pre-production phase of Cherenkov Telescope Array

“…The correct alignment between the optical axis of the telescope and laser beam is critical for successful measurements. Zemax ® simulations have been used to estimate the displacement from the infinity focus position of the telescope (de-focusing) of the FL to allow the optimal operations in the near field (better overlap) [4], without affecting the far field signals (Fig.3): for ranges > 500m the overlap efficiency remains constant (equal to its max value). Tests during actual measurements in atmosphere shown a slight higher value for the full overlap.…”