The Doppler lidar boundary-layer turbulence statistics value-added product

Description

The US Department of Energy’s Atmospheric Radiation Measurement (ARM) Climate Research Facility currently operates scanning coherent Doppler lidars at the Southern Great Plains (SGP) site, the Tropical Western Pacific site in Darwin, Australia (TWP-Darwin), and the first ARM Mobile Facility (AMF). Procurement of two additional systems is also planned for new sites at Oliktok Point on the North Slope of Alaska and on Graciosa Island in the Azores. These Doppler lidar systems operate in the near-infrared (IR) at a wavelength of 1500 nm and provide measurements of attenuated aerosol backscatter, clear-air vertical velocities, and horizontal wind profiles. Vertical velocities are currently acquired with a height resolution of 30 m and a temporal resolution of about 1 second. Since the instruments are sensitive to aerosol backscatter, measurements are generally confined to the lower troposphere (< 3 km above ground level [AGL]); however, accurate measurements are also often obtained from cloud bases or through optically thin cloud layers, up to the maximum measurement height of 10 km AGL.

Recently, the science community has expressed an interest in developing a Boundary-Layer Turbulence Statistics (BLTS) value-added product (VAP) from the raw Doppler lidar observations in order to reduce the raw data volume and more readily facilitate certain process studies. The focus of this poster is to present results from the new BLTS VAP that is currently under development. The BLTS VAP produces daily files containing 30-minute averaged profiles of vertical velocity variance, skewness, kurtosis, updraft fraction, cloud-base height, cloud fraction, cloud-base vertical velocity, as well as profiles of horizontal wind magnitude and direction. In addition to these lidar-derived quantities, the VAP also incorporates surface turbulent flux information from the eddy correlation (ECOR) systems, precipitation data, and cloud-base height estimates from the ceilometers. Noise correction methods are described and sample results showing profiles of vertical velocity variance, skewness, kurtosis, and updraft fraction are presented. Statistical composites of the daily BLTS VAP files are used to investigate the mean (monthly averaged) diurnal variation in these quantities at the SGP and TWP-Darwin sites. Additionally, cloud base height and cloud fraction estimates from the Doppler lidar and the ceilometer are compared.