B. L. Weber

Quality Controls for Profiler Measurements of Winds and RASS Temperatures

Abstract A new method for estimating winds and radio acoustic sounding system temperatures from radar Doppler measurements for the new NOAA wind profilers is described. This method emphasizes the quality of 6-min measurements prior to the computation of hourly averages. Compared with the older method currently being used, this new method provides measurements exhibiting better consistency and more complete coverage over height and time. Furthermore, it corrects aliased measurements.

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.

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...

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.

An Electronically Stabilized Phased Array System for Shipborne Atmospheric Wind Profiling

Abstract The design, construction, and first results are presented of a 915-MHz Doppler wind profiler that may be mounted on a moving platform such as a mobile land vehicle, ocean buoy, or a ship. The long dwell times in multiple beam directions, required for the detection of weak atmospheric radar echoes, are obtained by a passive phased array antenna, controlled by a motion control and monitoring (MCM) computer that acquires platform motion measurements and compensates in real time for the platform rotations. The platform translational velocities are accounted for in the signal processing system (SPS) before the calculation of the wind velocity profiles. The phased array antenna, MCM, and SPS are described, and radar-derived wind profiles are compared with those from rawinsonde balloons released during the first test cruise of the system, as the NOAA R/V Ronald H. Brown performed ship maneuvers.

Optimal Generation of Radar Wind Profiler Spectra

Abstract Radar wind profilers (RWPs) sense the mean and turbulent motion of the clear air through Doppler shifts induced along several (3–5) upward-looking beams. RWP signals, like all radars signals, are often contaminated. The contamination is clearly evident in the associated Doppler spectra, and automatic routines designed to extract meteorological quantities from these spectra often yield inaccurate results. Much of the observed contamination is due to an aliasing of higher frequency signals into the clear-air portion of the spectrum and a broadening of the spectral contaminants caused by the relatively short time series used to generate Doppler spectra. In the past, this source of contamination could not be avoided because of limitations on the size and speed of RWP processing computers. Today’s computers, however, are able to process larger amounts of data at greatly increased speeds. Here it is shown how standard and well-known spectral processing methods can be applied to significantly longer tim...

An Overview of the Mobile Profiler System: Preliminary Results from Field Tests during the Los Angeles Free-Radical Study

Abstract The System Demonstration and Integration Division of the Environmental Technology Laboratory and the Battlefield Environment Directorate of the U.S. Army Research Laboratory have designed and built the Mobile Profiler System (MPS).The MPS is an integrated system of ground-based and satellite-borne remote sensors that measure nearly continuous wind and temperature profiles from the surface up through the troposphere. Ground-based sensors include a 924-MHz phased-array wind and temperature profiler, a four-channel microwave radiometer, a surface meteorological tower, and a balloon sounding system. Although MPS was initially developed for military applications, the nonmilitary environmental applications are numerous and significant. This paper provides an overview of the instrumentation, software networking, data processing, data integration, and near real-time data display capabilities currently incorporated into the MPS. Initial results from the first field tests (Los Angeles Free-Radical Study, 3...

Effects of Small-Scale Vertical Motion on Radar Measurements of Wind and Temperature Profiles

Abstract Vertical velocities were observed during the month of June 1990 with two side-by-side wind profilers at Platteville, Colorado. Many of the observations reveal strong wave motion, probably mountain lee waves, that sometimes caused vertical velocity changes of several meters per second in less than an hour. It is demonstrated that, under these conditions, hourly averages cannot always be used to accurately account for the effects of vertical motion on the profiler measurements. It is also shown that it is impossible to accurately remove the effects of vertical motion from the horizontal wind component estimates when the horizontal scale of vertical-motion variability is comparable to the horizontal separation distance between antenna beams. The Radio Acoustic Sounding System (RASS) temperature measurements, however, are not affected by the small spatial scales because those measurements are made on the same vertical antenna beam as the vertical velocity measurements. Nevertheless, it is important t...

A Compact Direction-Finding Antenna for HF Remote Sensing

A compact four-element antenna, along with a numerical direction-finding algorithm, is analyzed using computer simulations that model sea-echo data obtained with an HF pulsed Doppler radar. The algorithm consists of closed-form expressions and is capable of deriving the angles-of-arrival for one or two signals impinging upon the antenna. Errors associated with the calculated angles are presented as a function of signal-to-noise ratio. In addition, it is demonstrated that preaveraging antenna voltages over independent data samples can decrease the angle errors and extend the range of the radar.