Richard G. Strauch

The Colorado Wind-Profiling Network

Abstract Remote sensing instrumentation has advanced to the point where serious consideration is being given to a next-generation tropospheric sounding system that uses radars and radiometers to provide profiles of tropospheric variables continuously and automatically. A network of five wind-profiling radars has been constructed in Colorado. This network represents a significant step in the development of a new observing system for operational and research meteorology. The radars and their capabilities and limitations are described.

Temperature sounding by RASS with wind profiler radars: a preliminary study

The radio acoustic sounding system (RASS) is a method of remotely measuring atmospheric temperature profiles by combining acoustic and radar techniques. This method has been applied to wind profiler radars in Colorado, and excellent performance in both height coverage and accuracy has been obtained. Various acoustic source functions are examined, and it is shown that FM-CW acoustic signals are less susceptible to error than pulsed acoustic systems when using pulsed radars for RASS. The remotely determined temperature profiles are compared with co-located radiosonde soundings, and good agreement is found. >

The Precision and Relative Accuracy of Profiler Wind Measurements

Abstract Two independent wind profiles were measured every hour during February 1986 with a five-beam, UHF (405 MHz) wind Profiler at Platteville, Colorado. Our analysis of the horizontal wind components over all heights for the entire month gave a standard deviation of about 1.3 m s−1 for the measurement errors one can expect for three-beam Profilers in clear air. This study demonstrated that it is important to include the effects of large vertical motion (caused by gravity waves or precipitation in the horizontal wind component measurements. These vertical motions were large enough to raise the error in the horizontal wind components to 1.7 m s−1 in two-beam configurations where no corrections are made for the vertical motion.

An Examination of Wind Profiler Signal Processing Algorithms

Abstract A numerical model to simulate radar data is used for testing various estimators of the Doppler shift in Doppler radar echoes. The estimators are the pulse pair and poly-pulse pair algorithms in the correlation domain, a least-squares fitting to the spectral peak of the power spectra, and direct calculations of the moments from periodograms in the spectral domain. Two averaging schemes (a consensus average and a median filter) are also examined for data with poor signal-to-noise ratios. The data processing method used in Doppler radar wind profilers, which operate over a very wide range of signal to noise ratios, is examined in detail. It is shown that the direct moment calculation combined with a consensus averaging technique has the best overall performance for accuracy and the ability to use data with a very low signal-to-noise ratio.

Preliminary Evaluation of the First NOAA Demonstration Network Wind Profiler

Abstract The first wind profiler for a demonstration network of wind profilers recently passed the milestone of 300 h of continuous operation. The horizontal wind component measurements taken during that period are compared with the WPL Platteville wind profiler and the NWS Denver rawinsonde. The differences between the network and WPL wind profilers have standard deviations of 2.30 m s−1 and 2.16 m s−1 for the u- and v-components, respectively. However, the WPL wind profiler ignores vertical velocity, whereas the network radar measures it and removes its effects from the u- and v-component measurements. The differences between the network wind profiler and the NWS rawinsonde (separated spatially by about 50 km) have standard deviations of 3.65 m s−1 and 3.06 m s−1 for the u- and v-components, respectively. These results are similar to those found in earlier comparison studies. Finally, the new network wind profiler demonstrates excellent sensitivity, consistently reporting measurements at all heights msl...

The Accuracy of RASS Temperature Measurements

Abstract Temperature measurements obtained using radiosondes and Radio Acoustic Sounding Systems (RASS) are compared to assess the utility of the RASS technique for meteorological studies. The agreement is generally excellent; rms temperature differences are about 1.0°C for comparisons during a variety of meteorological conditions. Observations taken under ideal circumstances indicate that a precision of about 0.2°C is achievable with the RASS technique. A processor being designed for RASS should allow routine temperature measurements approaching this precision.

Effects of Precipitation on UHF Wind Profiler Measurements

Abstract Horizontal winds in the presence of precipitation were measured routinely with a UHF (405 MHz) Wind Profiler. The profiler had five beam-pointing positions so independent measurements of horizontal winds could be compared to determine relative accuracy and precision. Large precipitation fall speeds are shown to cause very large errors (on the order of tens of meters per second) in the horizontal wind estimates when those fall speeds are not properly included in the estimates. But when the precipitation fall speeds are properly included, the errors are much smaller (2–4 m s−1), approaching those of clear air (1 m s−1). The decrease in the precision in precipitation is attributed largely to horizontal nonuniformity in precipitation from one antenna beam to another. A 4- or 5-beam profiler can detect conditions of horizontal inhomogeneity by virtue of its ability to make independent measurements of the winds from horizontally separated scattering volumes.

Single station radar ocean surface current mapper

A method and system for mapping ocean currents with a single radar. The radar is a pulsed monostatic radar operating in the HF/VHF range using a single transmitting antenna with a wide beam width. There is a linear array of antennas, each with its own receiver/digitizer system to sample the complex signal. The summing and phasing of the signals is done in software. The correlation functions are calculated using two successive complex Fourier transforms. The current vectors are measured as a function of range and angle from the radar site, thereby generating the current map.

Cloud Layers, Particle Identification, and Rain-Rate Profiles from ZRVf Measurements by Clear-Air Doppler Radars

Abstract Networks of radars that point almost vertically and continuously measure the vertical profile of the horizontal wind will, in the future, be operated at many locations around the world. Although such radars are designed to measure the Doppler-sensed movement of clear-air refractive-index inhomogeneities, they are an exceptional tool for sensing precipitating ice and water particles in clouds. Because of the low detection threshold and long averaging time of these radars water-particle-size distributions can be measured down to 100-µm diameter and mean vertical fall velocities Vf as small as 0.2 m s−1 can be accurately measured. In this paper, data are presented from two events in which clouds form, intensify, and finally produce precipitation. Height profiles are analyzed in terms of ZRVf plots versus height, where Z is the radar reflectivity factor and R is liquid flux (rainfall rate). The observations provide new insight into drop-growth and breakup processes. Special attention is given to the ...

Reducing the Effect of Ground Clutter on Wind Profiler Velocity Measurements

It is well known that the presence of ground clutter may severely bias radar measurements of the Doppler shift, particularly with wind profilers undertaking boundary layer measurements. It is shown both qualitatively and quantitatively with simulated data that a simple detrending of the time series data is often sufficient to significantly reduce the clutter problem. Finite impulse response filters are also investigated. Improvements are seen when long records are filtered prior to spectral analysis of the time series. The results are not very sensitive to the width of the filter (within reason) as long as the filter width encompasses the clutter spectrum.