Current Status of the ARM Raman Lidars

Poster PDF

Description

The ARM program currently operates three Raman lidars (RLs). The first system, at the Southern Great Plains (SGP) site in Oklahoma, has been operational since 1996. The second system was first located at the Tropical Western Pacific (TWP) site in Darwin, Australia in 2010, but has been operating at the Eastern North Atlantic (ENA) site in the Azores since 2015. The third system, located at the third ARM mobile facility (AMF3) at the North Slope of Alaska (NSA) site at Oliktok Point, Alaska, became operational in 2014, though its operation has been sporadic due to environmental challenges (and it is not currently operating). All three systems, which incorporate a similar design, transmit at 355 nm and use nine detection channels for measurement of elastic backscatter and depolarization, Raman backscatter due to vibrational transitions in atmospheric H2O (at 408 nm) and N2 (at 387 nm), and rotational transitions in O2 and N2 (at 353 nm and 354 nm). Raw photon counting and analog voltage data are recorded with a vertical resolution of 7.5 m and temporal resolution of 10 s. These raw data are then further averaged in time and height and used to compute various value-added data products (VAPs) such as profiles of water vapor mixing ratio, temperature, aerosol backscatter, aerosol extinction and linear depolarization ratio. Several other profiling systems were operated at the SGP site during 2017, including a prototype Vaisala DIAL (Differential Absorption Lidar) system (May-June 2017), the University of Hohenheim’s Raman lidar and water vapor DIAL during the Land-Atmosphere Feedback Experiment (LAFE; August 2017), and the AERI (Atmospheric Emitted Radiance Interferometer) instrument. The poster will include comparisons of profiles measured with these systems. The poster will also describe the new LabVIEW software that now operates the Raman lidars. The original software had been patched many times since 1996, and had diverged into three packages (customized for the three systems), greatly complicating maintenance of the software. It was refactored into much cleaner code last year, with a single version now operating all three systems.