Dataset: 	Water vapor density profiles
Instrument: 	NCAR Water Vapor Differential Absorption Lidar (nDIAL) - Unit #2
Contact: 	Dr. Scott Spuler and Dr. Matt Hayman, National Center for Atmospheric Research
Email: 		spuler@ucar.edu, mhayman@ucar.edu
Date: 		26 February 2018

Information:

The Earth Observing Laboratory (EOL) at the National Center for Atmospheric Research (NCAR) developed a diode-based micropulse differential absorption lidar to measure profiles of water vapor density in the atmospheric boundary layer (Spuler et al. AMT 2015).  Water vapor from this system has been compared against radiosondes and other sensors, and demonstrated very good accuracy and resolution (Weckwerth et al. JTECH 2016).  This lidar was deployed at the ARM intermediate facility I9 site (36.4761 degN, 97.4217 degW), which is about 16 km south-southeast of the ARM SGP Central Facility.  The DIAL was colocated with a 915 MHz radar wind profiler.  The DIAL fielded at LAFE was the second (unit #2) of a five node network under construction by NCAR in collaboration with Montana State University.  The instrument was operated from 28-Jul to 5-Sep 2017 (40 days) with an uptime of > 99%.  Due to software instability the instrument was not operational for about 8 hrs of the total project – approximately 2 hrs per outage, dispersed over multiple intervals (one unfortunate period of downtime occurred during the solar eclipse on 21-Aug).  

An experimental High Spectral Resolution Lidar (HSRL) channel was included for this deployment.  The newly integrated hardware allowed for the measurement of quantitative backscatter coefficients at 780 nm wavelength. Details of the technique, implementation and data processing can be found in Hayman and Spuler (Opt. Express 2017).  The HSRL channel operated from 9-Aug to 5-Sep 2017 (28 days).

This is version 1 of this dataset.  It was generated with a Python-based processing at 5 min temporal resolution, 37.5 m vertical grid spacing for the water vapor (absolute humidity).  The raw online and offline channels are run through a temporal Poisson denoising algorithm where each row of altitude bins are denoised in succession.  The data also includes a denoised 780 nm backscatter coefficient at 1 min temporal resolution, 37.5 m vertical grid spacing. 

Additional analysis of these data may necessitate an additional release of an updated version.

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