A Status Update on the ARM Raman Lidars

 

Authors

John E. M. Goldsmith — Sandia National Laboratories
Rob K Newsom — Pacific Northwest National Laboratory
Tyler Thorsen — NASA - Langley Research Center
Duli Chand — Pacific Northwest National Laboratory
Chitra Sivaraman — Pacific Northwest National Laboratory

Category

ARM infrastructure

Description

The ARM Facility currently operates Raman lidars (RLs) at the Southern Great Plains (SGP) site in Oklahoma, the Eastern North Atlantic (ENA) site in the Azores, and the third ARM mobile facility (AMF3) at Oliktok Point, Alaska. All three systems, which incorporate a similar design, transmit at 355 nm and use nine detection channels for measurement of elastic backscatter and 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. During the fall of 2015 the SGP RL, which had been in operation at the SGP site since 1996, was upgraded and relocated to the radar cluster in the middle of the SGP Central Facility. The ENA system began operation on Graciosa Island in September, 2015, after relocation from its previous deployment at the Tropical Western Pacific site in Darwin, Australia. The AMF3 RL, which is the newest of the three ARM RL systems, began operation at the Oliktok site in October of 2014. Algorithms for computing the RL VAPs have recently been upgraded, and efforts are underway to incorporate these algorithms into the ARM Data Integrator within the Data Management Facility. The water vapor mixing ratio and temperature retrieval algorithms have been completely overhauled to remove non-functional legacy code and improve the stability of the calibration and overlap correction procedures. The aerosol data products are now being generated using the Thorsen Feature detection and EXtinction (FEX) algorithm. This poster summarizes the current state of the ARM RLs and the VAPs that are derived from the raw measurements.