The authors describe and present early results from the July–August 1996 Lidars in Flat Terrain (LIFT) experiment. LIFT was a boundary layer experiment that made use of recently developed Doppler, aerosol backscatter, and ozone lidars, along with radars and surface instrumentation, to study the structure and evolution of the convective boundary layer over the very flat terrain of central Illinois. Scientific goals include measurement of fluxes of heat, moisture, and momentum; vertical velocity statistics; study of entrainment and boundary layer height; and observation of organized coherent structures. The data collected will also be used to evaluate the performance of these new lidars and compare measurements of velocity and boundary layer height to those obtained from nearby radar wind profilers. LIFT was a companion to the Flatland96 experiment, described by Angevine et al.

Abstract

The National Center for Atmospheric Research (NCAR) Improved Moments Algorithm (NIMA) calculates the first and second moments (radial velocity and spectral width) of wind-profiler Doppler spectra and provides an evaluation of confidence in these calculations. The first moments and their confidences are used by the NCAR Winds And Confidence Algorithm (NWCA), to estimate the horizontal wind. NIMA–NWCA has been used for several years in a real-time application for three wind profilers in Juneau, Alaska. This paper presents results of an effort to evaluate the first moments produced by NIMA and horizontal winds produced by NIMA–NWCA through comparison with estimates from “human experts” and also presents a comparison of NIMA–NWCA winds with in situ aircraft measurements. NIMA uses fuzzy logic to separate the atmospheric component of Doppler spectra from ground clutter and other sources of interference. The fuzzy logic rules are based on similar features humans consider when identifying atmospheric and contamination signals in Doppler spectra. Furthermore, NIMA attempts to mimic the human experts’ assignment of confidence to the moments. A Human Moment Analysis (HMA) tool was developed to assist the human experts in quantifying moments. This tool is described and a methodology of tuning NIMA rules based on human truth specification is presented. NIMA performed well on a dataset specifically chosen to be difficult. The average absolute error between the HMA estimate and NIMA-derived radial wind estimate was slightly more than 0.3 m s⁻¹ when data with low NIMA confidence were excluded, which is comparable to the Doppler spectrum resolution. The correlation between winds derived from NIMA–NWCA and from HMA first-moment estimates exceeded 0.96 when the data with low NWCA confidence were excluded. The correlation coefficient between NIMA winds and in situ measurements by aircraft was 0.93 when aircraft winds that were believed to be accurate were used.

The Terrain-Induced Rotor Experiment (T-REX) is a coordinated international project, composed of an observational field campaign and a research program, focused on the investigation of atmospheric rotors and closely related phenomena in complex terrain. The T-REX field campaign took place during March and April 2006 in the lee of the southern Sierra Nevada in eastern California. Atmospheric rotors have been traditionally defined as quasi-two-dimensional atmospheric vortices that form parallel to and downwind of a mountain ridge under conditions conducive to the generation of large-amplitude mountain waves. Intermittency, high levels of turbulence, and complex small-scale internal structure characterize rotors, which are known hazards to general aviation. The objective of the T-REX field campaign was to provide an unprecedented comprehensive set of in situ and remotely sensed meteorological observations from the ground to UTLS altitudes for the documentation of the spatiotemporal characteristics and internal structure of a tightly coupled system consisting of an atmospheric rotor, terrain-induced internal gravity waves, and a complex terrain boundary layer. In addition, T-REX had several ancillary objectives including the studies of UTLS chemical distribution in the presence of mountain waves and complex-terrain boundary layer in the absence of waves and rotors. This overview provides a background of the project including the information on its science objectives, experimental design, and observational systems, along with highlights of key observations obtained during the field campaign.

Constellations of driftsonde systems— gondolas floating in the stratosphere and able to release dropsondes upon command— have so far been used in three major field experiments from 2006 through 2010. With them, high-quality, high-resolution, in situ atmospheric profiles were made over extended periods in regions that are otherwise very difficult to observe. The measurements have unique value for verifying and evaluating numerical weather prediction models and global data assimilation systems; they can be a valuable resource to validate data from remote sensing instruments, especially on satellites, but also airborne or ground-based remote sensors. These applications for models and remote sensors result in a powerful combination for improving data assimilation systems. Driftsondes also can support process studies in otherwise difficult locations—for example, to study factors that control the development or decay of a tropical disturbance, or to investigate the lower boundary layer over the interior Antarctic continent. The driftsonde system is now a mature and robust observing system that can be combined with flight-level data to conduct multidisciplinary research at heights well above that reached by current research aircraft. In this article we describe the development and capabilities of the driftsonde system, the exemplary science resulting from its use to date, and some future applications.

The Concordiasi project is making innovative observations of the atmosphere above Antarctica. The most important goals of the Concordiasi are as follows:

• To enhance the accuracy of weather prediction and climate records in Antarctica through the assimilation of in situ and satellite data, with an emphasis on data provided by hyperspectral infrared sounders. The focus is on clouds, precipitation, and the mass budget of the ice sheets. The improvements in dynamical model analyses and forecasts will be used in chemical-transport models that describe the links between the polar vortex dynamics and ozone depletion, and to advance the under understanding of the Earth system by examining the interactions between Antarctica and lower latitudes.

• To improve our understanding of microphysical and dynamical processes controlling the polar ozone, by providing the first quasi-Lagrangian observations of stratospheric ozone and particles, in addition to an improved characterization of the 3D polar vortex dynamics. Techniques for assimilating these Lagrangian observations are being developed.

A major Concordiasi component is a field experiment during the austral springs of 2008–10. The field activities in 2010 are based on a constellation of up to 18 long-duration stratospheric super-pressure balloons (SPBs) deployed from the McMurdo station. Six of these balloons will carry GPS receivers and in situ instruments measuring temperature, pressure, ozone, and particles. Twelve of the balloons will release dropsondes on demand for measuring atmospheric parameters. Lastly, radiosounding measurements are collected at various sites, including the Concordia station.