Wind Profiler System Research Articles

Strengthening the three-dimensional comprehensive observation system of multi-layer interaction on the Tibetan Plateau to cope with the warming and wetting trend

Changes in the water cycle on the Tibetan Plateau (TP) have a significant impact on local agricultural production and livelihoods and its downstream regions. Against the background of widely reported warming and wetting, the hydrological cycle has accelerated and the likelihood of extreme weather events and natural disasters occurring (i.e., snowstorms, floods, landslides, mudslides, and ice avalanches) has also intensified, especially in the high-elevation mountainous regions. Thus, an accurate estimation of the intensity and variation of each component of the water cycle is an urgent scientific question for the assessment of plateau environmental changes. Following the transformation and movement of water between the atmosphere, biosphere and hydrosphere, the authors highlight the urgent need to strengthen the three-dimensional comprehensive observation system (including the eddy covariance system; planetary boundary layer tower; profile measurements of temperature, humidity, and wind by microwave radiometers, wind profiler, and radiosonde system; and cloud and precipitation radars) in the TP region and propose a practical implementation plan. The construction of such a three-dimensional observation system is expected to promote the study of environmental changes and natural hazards prevention.摘要青藏高原的水循环变化对于高原及其下游区域人类的生产生活具有举足轻重的影响. 在高原暖湿化的背景下, 其水文循环加快, 极端天气和自然灾害事件概率增大, 比如, 雪灾, 洪水, 滑坡, 泥石流, 冰崩在山区频发. 因此, 如何准确的估算青藏高原水循环各分量的大小及变化幅度是评估高原环境变化影响亟需解决的科学问题. 根据水在各圈层间转换过程, 我们提出了建立第三极地区 (尤其是复杂山区) 的三维立体多圈层地气相互作用综合观测系统(包括涡动相关系统, 行星边界层塔, 微波辐射计, 风廓线仪和无线电探空系统观测的风温湿廓线及云雨雷达等)的紧迫性和具体方案, 进而为研究青藏高原环境变化和山区灾害预测服务.

Doppler Profile Tracing Using MPCF on MU Radar and Sodar: Performance Analysis

Wind profilers (WPs) are ground-based pulsed Doppler radars operating in the UHF/very high frequency (VHF) bands. They use backscatter from clear-air turbulence as a tracer of background wind in the troposphere and up to mesosphere. Wind profiling systems range from large research radar systems to smaller operational units. In recent times, multiparameter cost function (MPCF) has emerged as a computationally efficient Doppler profile estimation method. It has been claimed that the MPCF method can be easily migrated to any vertically sounding clear-air wind profiling system that works in Doppler beam swinging mode. In order to investigate this claim, MPCF was applied to the following wind profiling systems: the middle and upper atmosphere (MU) radar, located at Shigaraki, Japan, which is an active phased array VHF radar system with 475 transceivers, and Doppler sodar, located at Pune, India, which uses acoustic frequency to obtain echoes in the planetary boundary layer. Both these systems are complementary in the sense that they cover ranges from ground to about 80 km. During the experimentation, the MPCF algorithm did not need any change of parameters except the matching of the data reading formats. The results of MPCF on the MU radar were validated with Radiosonde data. These results indicate that the MPCF works seamlessly on all types of WP systems irrespective of the carrier, range, and radar type.

A Summary of Convective-Core Vertical Velocity Properties Using ARM UHF Wind Profilers in Oklahoma

AbstractThis study presents a summary of the properties of deep convective updraft and downdraft cores over the central plains of the United States, accomplished using a novel and now-standard Atmospheric Radiation Measurement Program (ARM) scanning mode for a commercial wind-profiler system. A unique profiler-based hydrometeor fall-speed correction method modeled for the convective environment was adopted. Accuracy of the velocity retrievals from this effort is expected to be within 2 m s−1, with minimal bias and base core resolution expected near 1 km. Updraft cores are found to behave with height in reasonable agreement with aircraft observations of previous continental convection, including those of the Thunderstorm Project. Intense updraft cores with magnitudes exceeding 15 m s−1are routinely observed. Downdraft cores are less frequently observed, with weaker magnitudes than updrafts. Weak, positive correlations are found between updraft intensity (maximum) and updraft diameter length (coefficientrto 0.5 aloft). Negligible correlations are observed for downdraft core lengths and intensity.

Numerical modelling of a wind profiler system based on bubble tracking

Measuring atmospheric wind profiles is a difficult task which requires advanced, and normally expensive, technologies. The goal of this work is to provide the mathematical basis for a new and affordable system aiming at measuring local wind speed profiles by remotely tracking lighter-than-air bubbles. First of all, a detailed description of the system elements and the general configuration is included, followed by the mathematical tools involved in the measuring and filtering process. The capability of the proposed system to properly describe the horizontal wind in real time along the ascending path of the targets is modelled and verified with simulated scenarios. These simulations allowed to assess the accuracy and numerical stability of the measuring process as well as the relevance of different involved parameters. Results of simulated and field tests show the feasibility of the whole system and provide valuable data about optimal configuration. The success achieved in this preliminary work encourages us to move forward in the development of a prototype. It is expected that the operational version of the system could be a low-cost alternative to other wind profilers in certain conditions and applications, especially those related to air traffic management.

The Landfall and Inland Penetration of a Flood-Producing Atmospheric River in Arizona. Part I: Observed Synoptic-Scale, Orographic, and Hydrometeorological Characteristics

AbstractAtmospheric rivers (ARs) are a dominant mechanism for generating intense wintertime precipitation along the U.S. West Coast. While studies over the past 10 years have explored the impact of ARs in, and west of, California’s Sierra Nevada and the Pacific Northwest’s Cascade Mountains, their influence on the weather across the intermountain west remains an open question. This study utilizes gridded atmospheric datasets, satellite imagery, rawinsonde soundings, a 449-MHz wind profiler and global positioning system (GPS) receiver, and operational hydrometeorological observing networks to explore the dynamics and inland impacts of a landfalling, flood-producing AR across Arizona in January 2010. Plan-view, cross-section, and back-trajectory analyses quantify the synoptic and mesoscale forcing that led to widespread precipitation across the state. The analyses show that a strong AR formed in the lower midlatitudes over the northeastern Pacific Ocean via frontogenetic processes and sea surface latent-heat fluxes but without tapping into the adjacent tropical water vapor reservoir to the south. The wind profiler, GPS, and rawinsonde observations document strong orographic forcing in a moist neutral environment within the AR that led to extreme, orographically enhanced precipitation. The AR was oriented nearly orthogonal to the Mogollon Rim, a major escarpment crossing much of central Arizona, and was positioned between the high mountain ranges of northern Mexico. High melting levels during the heaviest precipitation contributed to region-wide flooding, while the high-altitude snowpack increased substantially. The characteristics of the AR that impacted Arizona in January 2010, and the resulting heavy orographic precipitation, are comparable to those of landfalling ARs and their impacts along the west coasts of midlatitude continents.

A Multiscale Observational Case Study of a Pacific Atmospheric River Exhibiting Tropical–Extratropical Connections and a Mesoscale Frontal Wave

A case study is presented of an atmospheric river (AR) that produced heavy precipitation in the U.S. Pacific Northwest during March 2005. The study documents several key ingredients from the planetary scale to the mesoscale that contributed to the extreme nature of this event. The multiscale analysis uses unique experimental data collected by the National Oceanic and Atmospheric Administration (NOAA) P-3 aircraft operated from Hawaii, coastal wind profiler and global positioning system (GPS) meteorological stations in Oregon, and satellite and global reanalysis data. Moving from larger scales to smaller scales, the primary findings of this study are as follow: 1) phasing of several major planetary-scale phenomena influenced by tropical–extratropical interactions led to the direct entrainment of tropical water vapor into the AR near Hawaii, 2) dropsonde observations documented the northward advection of tropical water vapor into the subtropical extension of the midlatitude AR, and 3) a mesoscale frontal wave increased the duration of AR conditions at landfall in the Pacific Northwest.

Mean vertical motions and their time‐height variations in the lower troposphere obtained from a UHF wind profiler at Pune, a tropical Indian station

A 404 MHz wind profiler (UHF radar) system has been in continuous operation since June 2003 at Pune (18°32′N, 73°51′E), a tropical Indian station. The system enables measurement of all three components (zonal, meridional and vertical) of the wind field with height coverage from 1.05 km to about 10 km and a height resolution of 300 m. Daily mean profile data of vertical velocity in the lower troposphere obtained during the 3‐year period, June 2003 to May 2006, has been used in this study to investigate the long‐term mean clear‐air vertical velocity, its variability, and seasonal/intraseasonal variations. Mean vertical velocities varied between −5.30 cm s−1 and +1.30 cm s−1, and mean vertical motions are predominantly downward at altitudes above 3 km. Significant seasonal variation in vertical velocity has been observed. During southwest monsoon months (June–September) a vertical two‐cell structure in vertical velocity has been noticed with upward motions below 4 km and downward motion above. In the premonsoon months (March–May) vertical motions are predominantly downward throughout the lower troposphere. Variability is larger during the monsoon and premonsoon seasons and is smaller during postmonsoon (October–November) and winter (December–February) seasons. Vertical velocities at altitudes below 3 km reveal significant semiannual and annual oscillations. Mean diurnal variations during SW monsoon period show interesting features. The observed variability in vertical velocities, especially in layers close to the surface, is explained to be due to the highly variable weather conditions on local as well as synoptic scale at this tropical station.

Boundary layer effects above a Himalayan valley near Mount Everest

Periodical Wind Profiler and Radio Acoustic Sounding System observations have been commenced at the Himalayas' northern slope nearby Mount Everest in September 2005. Primarily data sets obtained 25 km remote from the glacier edge are utilized for a preliminary discussion of planetary boundary layer circulation resembling high alpine mountainous regions. Substantial findings include the detection of two wind shears and the phenomenon of glacier wind at a distance of 25 km from the glaciers. The latter lead to a reversed compensatory flow in a vertical scale of up to 2000 m above ground level, pointing at supra regional impact.

Transport and Dispersion during Wintertime Particulate Matter Episodes in the San Joaquin Valley, California

Data analysis and modeling were performed to characterize the spatial and temporal variability of wintertime transport and dispersion processes and the impact of these processes on particulate matter (PM) concentrations in the California San Joaquin Valley (SJV). Radar wind profiler (RWP) and radio acoustic sounding system (RASS) data collected from 18 sites throughout Central California were used to estimate hourly mixing heights for a 3-month period and to create case studies of high-resolution diagnostic wind fields, which were used for trajectory and dispersion analyses. Data analyses show that PM episodes were characterized by an upper-level ridge of high pressure that generally produced light winds through the entire depth of the atmospheric boundary layer and low mixing heights compared with nonepisode days. Peak daytime mixing heights during episodes were ~400 m above ground level (agl) compared with ~800 m agl during nonepisodes. These episode/nonepisode differences were observed throughout the SJV. Dispersion modeling indicates that the range of influence of primary PM emitted in major population centers within the SJV ranged from ~15 to 50 km. Trajectory analyses revealed that little intrabasin pollutant transport occurred among major population centers in the SJV; however, interbasin transport from the northern SJV and Sacramento regions into the San Francisco Bay Area (SFBA) was often observed. In addition, this analysis demonstrates the usefulness of integrating RWP/RASS measurements into data analyses and modeling to improve the understanding of meteorological processes that impact pollution, such as aloft transport and boundary layer evolution.

Profiles of katabatic flow in summer and winter over Coats Land, Antarctica

AbstractObservations from a novel autonomous Doppler sodar wind profiling system are described and analysed. These include the first continuous wintertime soundings of katabatic winds over Antarctica—a continent with which they are synonymous. During 2002 and 2003 over 2600 wind profiles were taken during ‘case‐studies’ of high‐resolution sounding lasting hours to days. These case‐studies have been subjectively classified as: synoptically driven, katabatically influenced (28 days); primarily katabatically driven flows (a subset of 16 days); or other flow types. The Doppler sodar observations were augmented by automatic weather station observations at the field site and further up the slope, as well as synoptic and upper‐air observations at Halley Research Station, some 50 km distant on the Brunt Ice Shelf.In primarily katabatic flows there is a systematic change in the shape and depth of the low‐level katabatic jet with wind speed. Relatively strong katabatic flows (maximum winds of typically 8–10 m s−1) have a jet maximum between 20 and 60 m above the surface and are relatively deep (up to 200 m); while moderate katabatic flows (4–8 m s−1) typically have a jet maximum between 3 and 30 m and are shallower (∼100 m), although they can also be more diffuse in structure with a wind speed maximum at higher altitude. In all katabatic flows there is backing of wind direction with height, consistent with decreasing friction away from the surface. During summertime katabatic flows there is a clear diurnal signature at all heights, although this is less pronounced in the surface layer where there seems to be a persistent 2–4 m s−1 katabatic flow during all case‐studies. Where the diurnal forcing results in an abrupt katabatic flow deceleration, i.e. what may be a katabatic ‘jump’, there is a concurrent vertical acceleration. Wind profiles from a recent numerical weather prediction study of idealized katabatic flows at this site compare favourably with selected mean profiles; the only significant difference is that the model's wind speed is too low over the lowest ∼10 m. Copyright © 2006 Royal Meteorological Society.

An Autonomous Doppler Sodar Wind Profiling System

Abstract An autonomous Doppler sodar wind profiling system has been designed, built, tested, and then deployed for 2 years at a remote site in Coats Land, Antarctica. The system is designed around a commercially available phased-array sodar (a Scintec flat-array sodar, FAS64) and powered from five modular power system units. Each power unit comprises two batteries, two photovoltaic solar panels, and two vertical axis wind generators, plus charging control and isolation circuitry. The sodar’s main processing unit is located at the antenna, but is controlled from a manned research station 50 km distant, in real time, by a line-of-sight UHF radio link. Data from an integral automatic weather station (AWS) are also transmitted over the radio link, allowing meteorologically informed decisions on whether or not to operate the Doppler sodar. Over the 2-yr experiment dozens of sounding episodes, lasting from a few hours to a few days, were obtained. Successful soundings were obtained in temperatures down to −33°C, and wind speeds up to 12 m s−1. In general, the wind data quality was good, but the range was disappointing, probably as a result of the strongly stable atmospheric conditions that were experienced. The wind profiling system that is described has been used to obtain the first remote wintertime observations of katabatic winds over the Antarctic continent.

The Radar-RASS spaced-antenna windprofiler, a tool to measure atmospheric turbulence

Recently a Radar-RASS spaced-antenna wind profiling system with four receiving antennas has been developed. The system was designed to use the RASS-signal for radar-interferometry measurements of high-resolution time-series of the 3-D wind vector. The use of the deterministic RASS-backscatter signal which is insensitive to clutter interferences from the ground or elevated targets makes this system a useful tool for turbulence observation in the atmospheric boundary layer. The well-known problem of overestimating the horizontal velocity using simple correlation algorithms, caused by decaying refraction pattern, had to be addressed carefully. Multiple published approaches to find the correct horizontal velocity in the frequency domain using power and cross spectra as well as in the time-domain using correlation-functions were compared to each other. Based on these comparisons the implementation of the most suitable algorithm for the present system together with problems like noise suppression or system constants estimation will be discussed. Results of field measurements will be presented and the performance of the system to derive high-resolution time series of the 3-D wind vector will be demonstrated. Average quantities will be compared with the results of a SODAR operated next to the RASS.

Scanning skies and ocean

On July 19, the new NOAA oceanographic research vessel, the Ronald H. Brown, was commissioned by Department of Commerce Secretary William M. Daley in Charleston, S.C. The 274‐foot ship was named after the late former Commerce Secretary who died in a plane crash in 1996, while on an overseas trade mission.Scientists will use advanced sampling and analytical instruments aboard the ship to collect atmospheric and ocean data that are critical to understanding global climate change. “With its Doppler radar, upper‐air sounding system, and wind profiler system, the Brown is a world‐class atmospheric research platform, making it unequaled in the domestic research fleet for sampling both the oceans and atmosphere and discovering the profound interactions that bind them,” said D. James Baker, Commerce undersecretary for oceans and atmosphere. The ship and its team of university and NOAA scientists departed from Charleston on July 21 for the its first scientific cruise.

Evaluation of Doppler radar velocity estimators

This paper evaluates mean velocity estimator performance for typical parameter regimes for the 404‐MHz National Oceanic and Atmospheric Administration weather radar, the 915‐MHz boundary layer profiler, and the 50‐MHz mesosphere‐stratosphere‐troposphere/stratosphere‐troposphere radar wind profiling systems. Performance of the velocity estimates is characterized by the fraction of outliers and the standard deviation of the good estimates. For low signal‐to‐noise ratio, modern estimators generally have better performance than the traditional techniques; however, modern estimators require more information to produce a velocity estimate. The boundary for useful velocity estimates can be determined from the performance curves.

The Chung‐Li VHF radar: Technical layout and a summary of initial results

The particular characteristics of the VHF mesosphere‐stratosphere‐troposphere (MST) radar and wind profiler system, operated at the National Central University in Chung‐Li, Taiwan, Republic of China, are described. These are the dual‐mode applications of the Doppler and the spaced antenna technique, where the latter is used in the conventional mode to determine the wind velocity as well as in the novel interferometer mode. A brief outline of the scientific rationale and the technical layout of this particular configuration of the Chung‐Li VHF radar is given. A generally applicable method for system performance checks by deducing principle radar data parameters before the data analysis has been developed and is briefly described. Receiver system and antenna calibration measurements with celestial radio sources are reported and prove the appropriateness of the antenna system. Radar reflectivity profiles, measured with vertical as well as with off‐vertical antenna beams, are presented and discussed. We also present height‐time‐reflectivity plots for quiet and disturbed weather conditions and reflect on their peculiarities. We show that the wind profiles measured with the conventional Doppler method and the spaced antenna method are in good agreement with radiosonde measurements. The spatial correlation parameters, deduced with the spaced antenna method, are consistent with results from other radars. We also discuss measurement capabilities to deduce the tropopause height with the Chung‐Li VHF radar. We also describe echo power variations due to focusing from reflectivity structures modulated by gravity waves and a brief case study of Kelvin‐Helmholtz instability. We finally outline future research directions which could be performed with the Chung‐Li VHF radar.

The Changing Atmosphere—Challenges and Opportunities

The Changing Atmosphere—Challenges and Opportunities

Acoustic sounding of the atmosphere after ten years

It has now been ten years since the Weapons Research Establishment in Australia precipitated the modern era of atmospheric acoustic sounding with the operation of their 15‐m dish‐equipped sounder in November 1966. The spectacular facsimile records of atmospheric structure resulting from this pioneering effort have caught the interest of a large segment of the atmospheric sciences community. The number of such sounders now operated around the world approaches 200. From the outset, the utility of the devices for measuring the height of temperature inversions as the atmosphere passes through its diurnal cycles was recognized, and this ability is being exploited by many industrial and governmental groups concerned with air pollution problems. In addition, the ability to quantitatively measure the intensity of the scattered sound has led to a much improved understanding of the structure of atmosphere turbulence. Frequency analysis of the scattered signals allows accurate measurements of the three dimensional winds throughout the planetary boundary layer, and several prototype wind profiling systems are now in routine operation. The discipline still has many problems to be solved and questions to be answered: Can small scale turbulence measurements be extrapolated to predict pollutant diffusion? Can molecular and scattering attenuation coefficients be determined well enough to enable accurate measurements of turbulence throughout the planetary boundary layer? Can advantage be made of the coherence properties of the transmitted signal? Can temperature and humidity profiles be measured acoustically? Can acoustic Doppler wind sensors utilizing modern digital techniques be made inexpensive enough for urban networks to be established?

Acoustic wind and wind-shear measuring system

An acoustic wind-profiling system designed to detect hazardous wind-shear conditions in the airport environment has been developed during the past four years. The system installed at Dulles International Airport consists of a vertically pointed transmitter surrounded by three receivers 290-m distant and separated by 120° in azimuth. Electronically steered receiver beams track the upward propagating transmitted tone burst and collect the scattered acoustic signals. The Doppler frequency shift of the returns is analyzed digitally to determine the horizontal wind at 20 height levels in 30-m increments. Unique design features of the system such as the steered receiver antenna are described. A one-leg prototype of the Dulles system was installed and tested at Table Mountain near Boulder, CO. Winds measured by the prototype acoustic system compared well with those determined by an FM-CW radar and a balloon-borne anemometer. Noise generated by rain and surface winds exceeding 16 m sec−1 proved to be the major limitations for the acoustic system. Preliminary results from the Dulles system are also presented.

Omega Windfinding Systems

Abstract Wind-profiling systems that use the retransmission of Omega navigation signals are described. Sources of error affecting the composite performance of the Omega system are highlighted, with emphasis on their effect on velocity estimates. Finally, the question of processing noisy phase data from the Omega system to yield optimal estimates of wind velocities is debated.