Abstract
We present a Rayleigh-Mie-Raman LIDAR system in operation at Clermont-Ferrand (France) since 2008. The system provides continuous vertical tropospheric profiles of aerosols, cirrus optical properties and water vapour mixing ratio. Located in proximity to the high altitude Puy de Dôme station, labelled as the GAW global station PUY since August 2014, it is a useful tool to describe the boundary layer dynamics and hence interpret in situ measurements. This LIDAR has been upgraded with specific hardware/software developments and laboratory calibrations in order to improve the quality of the profiles, calibrate the depolarization ratio, and increase the automation of operation. As a result, we provide a climatological water vapour profile analysis for the 2009–2013 period, showing an annual cycle with a winter minimum and a summer maximum, consistent with in-situ observations at the PUY station. An overview of a preliminary climatology of cirrus clouds frequency shows that in 2014, more than 30% of days present cirrus events. Finally, the backscatter coefficient profile observed on 27 September 2014 shows the capacity of the system to detect cirrus clouds at 13 km altitude, in presence of aerosols below the 5 km altitude.
Highlights
Since the beginning of the 20th century, the increase of anthropogenic atmospheric emissions has induced an evolution of the atmospheric composition which needs to be surveyed and understood, in order to improve climate projections [1]
The objective of this paper is to provide a detailed description of the Light Detection and Ranging (LIDAR) system, the scientific and technical motivations for improvements and the modifications made on the system
If the glass is fixed on the frame with a polyurethane glue, the frame will apply on the glass a sufficient stress to induce birefringence in this material, and a depolarization of the light depending on the temperature, which cannot be acceptable for the LIDAR depolarization ratio measurement
Summary
Since the beginning of the 20th century, the increase of anthropogenic atmospheric emissions has induced an evolution of the atmospheric composition which needs to be surveyed and understood, in order to improve climate projections [1]. The satellites provide observations at a global scale, but with a low spatial resolution They may be completed by in situ and remote sensing observations from ground based stations in order to allow the study of dynamical and physico-chemical processes in all their complexity. Watch (GAW) program of the World Meteorological Organization (WMO) These stations provide reliable data on the physical properties and chemical composition of the atmosphere and contribute to the survey of climate. PUY is labelled as a GAW global station since August 2014 (and was a GAW regional station before), located around Clermont-Ferrand, a city of 150,000 inhabitants, near the centre of France, at the foothills of the “Chaîne des Puys” mountain ridge It hosts in-situ and remote sensing instruments, deployed in three sites at different altitudes, distant from less than 15 km far away from each other. Description of the data processing, examples of atmospheric profiles and overview of the database are provided
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