Madison J. Post

High-Resolution Doppler Lidar for Boundary Layer and Cloud Research

Abstract The high-resolution Doppler lidar (HRDL) was developed to provide higher spatial, temporal, and velocity resolution and more reliable performance than was previously obtainable with CO2-laser-based technology. The improved performance is needed to support continued advancement of boundary layer simulation models and to facilitate high-resolution turbulent flux measurements. HRDL combines a unique, eye-safe, near-IR-wavelength, solid-state laser transmitter with advanced signal processing and a high-speed scanner to achieve 30-m range resolution and a velocity precision of ∼10 cm s−1 under a variety of marine and continental boundary layer conditions, depending on atmospheric and operating conditions. An attitude-compensating scanner has been developed to facilitate shipboard marine boundary layer observations. Vertical velocities, fine details of the wind profile near the surface, turbulence kinetic energy profiles, and momentum flux are measurable with HRDL. The system is also useful for cloud s...

Optimizing a pulsed Doppler lidar.

NOAAs fieldable injection-seeded, pulsed, coherent CO(2) lidar was developed over a 5-yr period. Its performance and reliability are characterized. Techniques for calibration, alignment, collimation, and for improving detector performance and frequency stability are presented.

Lidar-Measured Winds from Space: A Key Component for Weather and Climate Prediction

Abstract The deployment of a space-based Doppler lidar would provide information that is fundamental to advancing the understanding and prediction of weather and climate. This paper reviews the concepts of wind measurement by Doppler lidar, highlights the results of some observing system simulation experiments with lidar winds, and discusses the important advances in earth system science anticipated with lidar winds. Observing system simulation experiments, conducted using two different general circulation models, have shown 1) that there is a significant improvement in the forecast accuracy over the Southern Hemisphere and tropical oceans resulting from the assimilation of simulated satellite wind data, and 2) that wind data are significantly more effective than temperature or moisture data in controlling analysis error. Because accurate wind observations are currently almost entirely unavailable for the vast majority of tropical cyclones worldwide, lidar winds have the potential to substantially improve...

Characteristics of coherent lidar returns from calibration targets and aerosols

A CO(2) heterodyne lidar system and high speed digitizer were used to examine properties of returns from disk and belt-type calibration targets and atmospheric aerosols. Amplitude statistics of the returns from the targets examined corresponded to those of the Rayleigh phasor predicted by theory. Returns from a belt sander fluctuated at a much slower rate than those from the disks or aerosols, requiring longer averaging times for accurate power measurement. At very close focal lengths returns from single large particles often domier nated the backscattered aerosol signal.

Feasibility studies for a global wind measuring satellite system (Windsat): analysis of simulated performance.

A detailed computer simulation of the Windsat global wind measuring process has been developed and used to establish error limits as a function of design parameters. Studies were conducted for a Windsat research system in a 300- and an 800-km orbit. Wind measuring errors were <2 m sec−1 in the troposphere for the recommended set of parameters. Our study results indicate the feasibility of measuring global winds from a space platform using a coherent laser radar.

Aerosol backscattering profiles at λ = 10.6 μm

A systematic program of observing atmospheric backscatter beta profiles from 4 to 16-km above sea level is described. Initial monthly averages indicating a lognormal distribution are presented. Cirrus prevalence, volcanic layers in the stratosphere, diurnal effects, convection, calibration, and absorption effects are discussed as well.

Receiving efficiency of monostatic pulsed coherent lidars. 1: Theory

The receiving efficiency eta as a function of range z is investigated for pulsed coherent lidars using a theory that relates eta(z) to the transmitted laser intensity and the point-source receiving efficiency eta(s)(r,z). The latter can be calculated either by a forward method, or by a backward method that employs the back-propagated local oscillator (BPLO) approach. The BPLO method is efficient and accurate provided that cascaded diffraction effects inside the lidar system are properly taken into account. The theory is applied to the ideal case to examine the optimization of the system when both transmitted and BPLO fields at the antenna are Gaussian, including optimum telescope aperture.

Observations of Pinatubo ejecta over Boulder, Colorado by lidars of three different wavelengths

NOAA lidars at wavelengths of 0.574, 0.694, and 10.591 μm have observed ejecta from the eruption of Mt. Pinatubo both in the troposphere and stratosphere over Boulder, Colorado, since July 27, 1991. Multilayered clouds have been highly variable on time scales of minutes to days. Measurements at multiple wavelengths provide valuable information on size distribution and the wavelength dependence of backscatter and optical depth.

Aerosol backscattering profiles at CO2 wavelengths: the NOAA data base.

NOAA’s data base for aerosol backscattering at λ = 10.6 μm since May 1981, in Boulder, Colorado, is presented together with seasonally averaged profiles and statistical analyses. Studies of the El Chichon event are included.

The Combined Sensor Program: An Air–Sea Science Mission in the Central and Western Pacific Ocean

Abstract Twelve national research organizations joined forces on a 30-day, 6800 n mi survey of the Central and Tropical Western Pacific on NOAAs Research Vessel Discoverer. The Combined Sensor Program (CSP), which began in American Samoa on 14 March 1996, visited Manus Island, Papua New Guinea, and ended in Hawaii on 13 April, used a unique combination of in situ, satellite, and remote sensors to better understand relationships between atmospheric and oceanic variables that affect radiative balance in this climatically important region. Besides continuously measuring both shortwave and longwave radiative fluxes, CSP instruments also measured most other factors affecting the radiative balance, including profiles of clouds (lidar and radar), aerosols (in situ and lidar), moisture (balloons, lidar, and radiometers), and sea surface temperature (thermometers and Fourier Transform Infrared Radiometers). Surface fluxes of heat, momentum, and moisture were also measured continuously. The Department of Energys ...