Scott P. Sandberg

A Bad Air Day in Houston

Abstract A case study from the Texas Air Quality Study 2000 field campaign illustrates the complex interaction of meteorological and chemical processes that produced a high-pollution event in the Houston area on 30 August 2000. High 1-h ozone concentrations of nearly 200 ppb were measured near the surface, and vertical profile data from an airborne differential-absorption lidar (DIAL) system showed that these high-ozone concentrations penetrated to heights approaching 2 km into the atmospheric boundary layer. This deep layer of pollution was transported over the surrounding countryside at night, where it then mixed out the next day to become part of the rural background levels. These background levels thus increased during the course of the multiday pollution episode. The case study illustrates many processes that numerical forecast models must faithfully represent to produce accurate quantitative predictions of peak pollutant concentrations in coastal locations such as Houston. Such accurate predictions ...

Doppler Lidar Estimation of Mixing Height Using Turbulence, Shear, and Aerosol Profiles

Abstract The concept of boundary layer mixing height for meteorology and air quality applications using lidar data is reviewed, and new algorithms for estimation of mixing heights from various types of lower-tropospheric coherent Doppler lidar measurements are presented. Velocity variance profiles derived from Doppler lidar data demonstrate direct application to mixing height estimation, while other types of lidar profiles demonstrate relationships to the variance profiles and thus may also be used in the mixing height estimate. The algorithms are applied to ship-based, high-resolution Doppler lidar (HRDL) velocity and backscattered-signal measurements acquired on the R/V Ronald H. Brown during Texas Air Quality Study (TexAQS) 2006 to demonstrate the method and to produce mixing height estimates for that experiment. These combinations of Doppler lidar–derived velocity measurements have not previously been applied to analysis of boundary layer mixing height—over the water or elsewhere. A comparison of the ...

Doppler Lidar–Based Wind-Profile Measurement System for Offshore Wind-Energy and Other Marine Boundary Layer Applications

AbstractAccurate measurement of wind speed profiles aloft in the marine boundary layer is a difficult challenge. The development of offshore wind energy requires accurate information on wind speeds above the surface at least at the levels occupied by turbine blades. Few measured data are available at these heights, and the temporal and spatial behavior of near-surface winds is often unrepresentative of that at the required heights. As a consequence, numerical model data, another potential source of information, are essentially unverified at these levels of the atmosphere. In this paper, a motion-compensated, high-resolution Doppler lidar–based wind measurement system that is capable of providing needed information on offshore winds at several heights is described. The system has been evaluated and verified in several ways. A sampling of data from the 2004 New England Air Quality Study shows the kind of analyses and information available. Examples include time–height cross sections, time series, profiles, ...

Preliminary measurements with an automated compact differential absorption lidar for the profiling of water vapor

The design and preliminary tests of an automated differential absorption lidar (DIAL) that profiles water vapor in the lower troposphere are presented. The instrument, named CODI (for compact DIAL), has been developed to be eye safe, low cost, weatherproof, and portable. The lidar design and its unattended operation are described. Nighttime intercomparisons with in situ sensors and a radiosonde are shown. Desired improvements to the lidar, including a more powerful laser, are also discussed.

Development and Application of a Compact, Tunable, Solid-State Airborne Ozone Lidar System for Boundary Layer Profiling

AbstractThe National Oceanic and Atmospheric Administration/Earth System Research Laboratory/Chemical Sciences Division (NOAA/ESRL/CSD) has developed a versatile, airborne lidar system for measuring ozone and aerosols in the boundary layer and lower free troposphere. The Tunable Optical Profiler for Aerosol and Ozone (TOPAZ) lidar was deployed aboard a NOAA Twin Otter aircraft during the Texas Air Quality Study (TexAQS 2006) and the California Research at the Nexus of Air Quality and Climate Change (CalNex 2010) field campaigns. TOPAZ is capable of measuring ozone concentrations in the lower troposphere with uncertainties of several parts per billion by volume at 90-m vertical and 600-m horizontal resolution from an aircraft flying at 60 m s−1. The system also provides uncalibrated aerosol backscatter profiles at 18-m vertical and 600-m horizontal resolution. TOPAZ incorporates state-of-the-art technologies, including a cerium-doped lithium calcium aluminum fluoride (Ce:LiCAF) laser, to make it compact an...

3D Volumetric Analysis of Wind Turbine Wake Properties in the Atmosphere Using High-Resolution Doppler Lidar

AbstractWind turbine wakes in the atmosphere are three-dimensional (3D) and time dependent. An important question is how best to measure atmospheric wake properties, both for characterizing these properties observationally and for verification of numerical, conceptual, and physical (e.g., wind tunnel) models of wakes. Here a scanning, pulsed, coherent Doppler lidar is used to sample a turbine wake using 3D volume scan patterns that envelop the wake and simultaneously measure the inflow profile. The volume data are analyzed for quantities of interest, such as peak velocity deficit, downwind variability of the deficit, and downwind extent of the wake, in a manner that preserves the measured data. For the case study presented here, in which the wake was well defined in the lidar data, peak deficits of up to 80% were measured 0.6–2 rotor diameters (D) downwind of the turbine, and the wakes extended more than 11D downwind. Temporal wake variability over periods of minutes and the effects of atmospheric gusts a...

Assessing State-of-the-Art Capabilities for Probing the Atmospheric Boundary Layer: The XPIA Field Campaign

AbstractTo assess current capabilities for measuring flow within the atmospheric boundary layer, including within wind farms, the U.S. Department of Energy sponsored the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign at the Boulder Atmospheric Observatory (BAO) in spring 2015. Herein, we summarize the XPIA field experiment, highlight novel measurement approaches, and quantify uncertainties associated with these measurement methods. Line-of-sight velocities measured by scanning lidars and radars exhibit close agreement with tower measurements, despite differences in measurement volumes. Virtual towers of wind measurements, from multiple lidars or radars, also agree well with tower and profiling lidar measurements. Estimates of winds over volumes from scanning lidars and radars are in close agreement, enabling the assessment of spatial variability. Strengths of the radar systems used here include high scan rates, large domain coverage, and availability during most precipita...

Depolarization and Backscatter Lidar for Unattended Operation

A depolarization and backscatter lidar for unattended, stand-alone eye safe operation has been developed and is undergoing tests at NOAA ETL. The system operates with a frequency doubled Nd:YLF micro-Joule pulse laser transmitter and employs a narrow field-of-view and narrow bandpass photon counting receiver. Monitoring, control, display, and data archiving are achieved through a network connection to a remote computer.

Scanning tropospheric ozone and aerosol lidar with double-gated photomultipliers

The Ozone Profiling Atmospheric Lidar is a scanning four-wavelength ultraviolet differential absorption lidar that measures tropospheric ozone and aerosols. Derived profiles from the lidar data include ozone concentration, aerosol extinction, and calibrated aerosol backscatter. Aerosol calibrations assume a clear air region aloft. Other products include cloud base heights, aerosol layer heights, and scans of particulate plumes from aircraft. The aerosol data range from 280 m to 12 km with 5 m range resolution, while the ozone data ranges from 280 m to about 1.2 km with 100 m resolution. In horizontally homogeneous atmospheres, data from multiple-elevation angles is combined to reduce the minimum altitude of the aerosol and ozone profiles to about 20 m. The lidar design, the characterization of the photomultiplier tubes, ozone and aerosol analysis techniques, and sample data are described. Also discussed is a double-gating technique to shorten the gated turn-on time of the photomultiplier tubes, and thereby reduce the detection of background light and the outgoing laser pulse.

Unattended spectrometer and lidar for measuring atmospheric radiation at Mauna Loa, Hawaii

A combined active-passive remote sensing system has been developed to study atmospheric radiation and cirrus cloud radiative properties at the NOAA Mauna Loa Observatory on the island of Hawaii. The active portion of this system is an eye-safe, dual-polarization lidar, while the passive portion is a Fourier transform spectro-radiometer operating in emission mode. The combined system allows unattended, remote measurements of infrared atmospheric emission and clouds with depolarization discrimination of ice and liquid.