Sound Detection And Ranging Research Articles

Regression analysis of Ventilation Coefficient at a semi-arid IGP region using forward selection technique

In this study, a forward selection (FS),technique has been employed for linear and multiple regression analysis of Ventilation coefficient(VC) with meteorological parameters and air pollutants concentrations;using a Remote sensing technique acoustic sounder i.e., SODAR (Sound Detection and ranging); it gives real-time continuous ABL (Atmospheric Boundary Layer) height data and attached meteorological sensors give meteorological parameters data such as wind speed/direction, relative humidity and temperature. The diurnal variability is a dominant feature of the ABL, which plays an important role in the exchanges of heat, momentum, moisture, and chemical constituents between the surface and free atmosphere. The ventilation coefficient is an atmospheric condition that indicates the air quality and pollution potential. The correlation of VC with different air pollutants concentrations are discussed and the effect of convection and wind speed on the ventilation coefficient is also analysed. Diurnal and seasonal variation of ventilation coefficient gives knowledge about the day to day weather phenomena for air quality management. The result shows that among nine variables (WS, RH, Temp, CO, PM2.5, SO2, NO2, Ozone, PM10), wind speed (WS), relative humidity (RH), temperature (Temp), and COare the highly influencing variable to the ventilation coefficient and these four best variables selected by FS can be used as an input parameter in any prediction model to get better performance in comparison to the nine variables.

Interpretation of Acousting Sounding Records with Meterological Parameters and Ventilation Coefficient Over Delhi

Atmospheric Boundary Layer (ABL) height is an important parameter in defining the Ventilation Coefficient (VC) of any area. In this work, SODAR (Sound Detection and Ranging) observed data of different echograms for the year 2020 has been used for structure identification. The interpretation of ecograms is often not straight-forward. In this paper, an interpretation of different echograms along with meteorological parameters over Delhi is described. The ecogram structures were interpreted along with VC analysis. It is observed from the structures that during foggy days, VC values vary from day to day in the winter, with daily maximum values occurring between 13:00 and 15:00 h. The daytime values varied significantly from sunrise to sunset, while the night-time values remained relatively stable (200 m2/s). However, due to fog diurnal variation from 16:00 h to 11:00 h, that is from evening to all night and then the next morning until 12:00 h, the atmospheric condition remained stable. At maximal wind speeds, a maximum VC of 1600 m2/s (at 12:00 h) was observed during extended fumigation. With minimal wind speeds and ABL height, a minimum VC of 100 m2/s (at 20:00 h) was observed. However, both VCs were smaller than the optimal VC for 6000 m2/s safe dispersion.

Indigenous Development of Acoustic Sounder (SODAR) in India as an upgraded technology for Environmental Protection: A Review

Sound Detection and Ranging (SODAR) has moved to the forefront of consumer technology due to the pressing need toengage the Atmospheric Boundary Layer (ABL) in environmental protection. An active ground-based remote sensingsystem (SODAR) is used to determine the lower-atmosphere wind profile and temperature structure. SODAR can detectturbulence parameters in the ABL from a distance and can be used for wind profiling. SODAR, with its significantlyenhanced capability, is expected to be a futuristic remote sensing device with several uses in the near future. Including anemphasis on its applications and current developments, this article examines SODAR's early history, with a review of Indianstudies. The article examines past breakthroughs in SODAR as well as its advancement and applications, with an emphasison India due to the worldwide nature of SODAR research. Additionally, the article discusses how effective SODAR is inprotecting the environment and how important it is going forward. After summarising the applications, various opportunitiesand barriers incurred in SODAR use, a proposed review article to provide insights into previously understudied, unstudied,and studied research work accomplished on SODAR in India is constructed. The article accentuates the role of SODAR asan environmental safeguarding tool.

A Three-Year Climatology of the Wind Field Structure at Cape Baranova (Severnaya Zemlya, Siberia) from SODAR Observations and High-Resolution Regional Climate Model Simulations during YOPP

Measurements of the atmospheric boundary layer (ABL) structure were performed for three years (October 2017–August 2020) at the Russian observatory “Ice Base Cape Baranova” (79.280° N, 101.620° E) using SODAR (Sound Detection And Ranging). These measurements were part of the YOPP (Year of Polar Prediction) project “Boundary layer measurements in the high Arctic” (CATS_BL) within the scope of a joint German–Russian project. In addition to SODAR-derived vertical profiles of wind speed and direction, a suite of complementary measurements at the observatory was available. ABL measurements were used for verification of the regional climate model COSMO-CLM (CCLM) with a 5 km resolution for 2017–2020. The CCLM was run with nesting in ERA5 data in a forecast mode for the measurement period. SODAR measurements were mostly limited to wind speeds <12 m/s since the signal was often lost for higher winds. The SODAR data showed a topographical channeling effect for the wind field in the lowest 100 m and some low-level jets (LLJs). The verification of the CCLM with near-surface data of the observatory showed good agreement for the wind and a negative bias for the 2 m temperature. The comparison with SODAR data showed a positive bias for the wind speed of about 1 m/s below 100 m, which increased to 1.5 m/s for higher levels. In contrast to the SODAR data, the CCLM data showed the frequent presence of LLJs associated with the topographic channeling in Shokalsky Strait. Although SODAR wind profiles are limited in range and have a lot of gaps, they represent a valuable data set for model verification. However, a full picture of the ABL structure and the climatology of channeling events could be obtained only with the model data. The climatological evaluation showed that the wind field at Cape Baranova was not only influenced by direct topographic channeling under conditions of southerly winds through the Shokalsky Strait but also by channeling through a mountain gap for westerly winds. LLJs were detected in 37% of all profiles and most LLJs were associated with channeling, particularly LLJs with a jet speed ≥ 15 m/s (which were 29% of all LLJs). The analysis of the simulated 10 m wind field showed that the 99%-tile of the wind speed reached 18 m/s and clearly showed a dipole structure of channeled wind at both exits of Shokalsky Strait. The climatology of channeling events showed that this dipole structure was caused by the frequent occurrence of channeling at both exits. Channeling events lasting at least 12 h occurred on about 62 days per year at both exits of Shokalsky Strait.

Vertical Wind Profile Modeling at Low Levels Using a Regional Climate Model in a Case Study at the Alcântara Launch Center

This case study, using a regional climate model (RegCM-4.7) in high horizontal resolution, allowed to obtain information on the intensity of the average vertical wind profile over the Alcântara Launch Center (ALC), Brazil. In the literature, on the wind intensity, the lack of continuous monitoring of the existence of flows in the vertical profile of the wind at heights of 400 to 600 m and the measurement of its magnitude make it possible to have an estimate lower than what can occur in reality at a low level in the region for operational purposes for the rocket launch. Therefore, this works results points to an intraseasonal variability of the wind intensity with maximum winds of the order of 14 to 20 m·s-1 in the core wind intensity at heights of 600 m, corresponding to pressure levels of the order of 930 hPa, in August, September and October 2020. These intensity values should be further studied with the use of observation equipment such as sound detection and ranging (SODAR) in the continuation of this research, in moment future, as well; the global models of reanalysis have low resolution and are not suitable for comparisons.

Observed diurnal and intraseasonal variations in boundary layer winds over Ganges valley

The diurnal and intraseasonal variability in the surface winds are examined using high resolution measurements during the Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX) Phase III Integrated Ground based Experiment, conducted in the Ganges valley during 2014–15. The yearlong observations of lower boundary layer wind from the Ganges valley are discussed in this study. Wind speed and directions at the surface levels obtained from SOund Detection And Ranging (SODAR) and tower are compared and found, mostly SODAR measurements are consistent with tower during high wind conditions (greater than 4 ms−1) except under weak circumstances. Our analysis revealed that, the mean wind speed found to be a maximum (7.86 ms−1) during the monsoon season in the air layer between 10 m and 200 m level and shows a sharp increase near to the surface (at 20 m level). Analysis also depicts seasonal variations in wind speed are predominant in the lower boundary layer and it is closely linked to the large-scale flow patterns/disturbances. The turbulent kinetic energy (TKE) was found to be maximum at 165 m (0.62 m2s-2) during the pre-monsoon due to enhanced surface heating. The 93% and 75% of the wind speed profiles exhibited unstable conditions in the monsoon and post monsoon conditions. Moreover, the unstable layers are characterized by high wind speed and temperature structure function (CT2)in day time. On large scale, the wind speed gets strengthened (reduced) in the wet (dry) spell in the lower levels with distinct diurnal cycle in the Indo Gangetic Plain. The advection of moisture in the nocturnal periods in connection with the wet spells in the near surface level is observed and the wind speeds in the daytime (above 150 m) are also found to be stronger in the range 3.5–5 ms−1 in the dry spells due to the enhanced mixing. The diurnal cycle is more evident in the dry spells in the lower levels. Rainfall peak found in July 2014 is connected with the quasi-biweekly mode periodicity of 2–16 days and further, power spectrum analysis reveals that the presence of high frequency oscillations of periodicity less than 10 days and between 10 and 20 days in the surface layer parameters.

Quality and applications of wind data from sound detection and ranging (SODAR) equipment and microwave wind profilers

AbstractThe quality and applications of vertical velocity data from SODAR and radar wind profilers are examined in this paper. The vertical velocity data from collocated SODAR and boundary layer type wind profilers are compared for a period of 7 months. It is found that the two datasets are well correlated, but the slope of the linear fit to the data has a significant deviation from 1. This may be related to the difference in the sampling volumes of the vertical beams from the two instruments. The correlation for horizontal wind data was found to be much stronger. Three applications of the vertical velocity data are discussed: subsidence in the outer periphery of a tropical cyclone and in hazy weather, and the upward motion of the air in convective weather. Data such as those under study here are found to contribute significantly to the monitoring and understanding of weather conditions, and would be useful for the nowcasting of lowvisibility and convective weather.

Implementation of a Virtual Microphone Array to Obtain High Resolution Acoustic Images.

Using arrays with digital MEMS (Micro-Electro-Mechanical System) microphones and FPGA-based (Field Programmable Gate Array) acquisition/processing systems allows building systems with hundreds of sensors at a reduced cost. The problem arises when systems with thousands of sensors are needed. This work analyzes the implementation and performance of a virtual array with 6400 (80 × 80) MEMS microphones. This virtual array is implemented by changing the position of a physical array of 64 (8 × 8) microphones in a grid with 10 × 10 positions, using a 2D positioning system. This virtual array obtains an array spatial aperture of 1 × 1 m2. Based on the SODAR (SOund Detection And Ranging) principle, the measured beampattern and the focusing capacity of the virtual array have been analyzed, since beamforming algorithms assume to be working with spherical waves, due to the large dimensions of the array in comparison with the distance between the target (a mannequin) and the array. Finally, the acoustic images of the mannequin, obtained for different frequency and range values, have been obtained, showing high angular resolutions and the possibility to identify different parts of the body of the mannequin.

Wind characteristics observation using Doppler-SODAR for wind energy applications

This paper presents an application of Doppler SODAR (Sound Detection and Ranging) system for the as- sessment of wind characteristics at an onshore site in Tamil Nadu, India. The wind speed is statistically analyzed by means of Weibull distribution function and results were used to compute several charac- teristics parameters related to wind energy applications and no significant discrepancies were observed. The characteristics of wind shear coefficient were evaluated for different altitudes. The vertical profile of wind speed measured from SODAR system was compared with existing models. Furthermore, the tur- bulence characteristics were analyzed and compared along with the turbulence intensity. From the eco- nomic point of view the SODAR system was found to be cost-effective at higher heights. The results of this study are expected to provide useful information for the deployment of remote sensing instruments for wind energy development in India.

Wind characteristics observation using Doppler-SODAR for wind energy applications

This paper presents an application of Doppler SODAR (Sound Detection and Ranging) system for the assessment of wind characteristics at an onshore site in Tamil Nadu, India. The wind speed is statistically analyzed by means of Weibull distribution function and results were used to compute several characteristics parameters related to wind energy applications and no significant discrepancies were observed. The characteristics of wind shear coefficient were evaluated for different altitudes. The vertical profile of wind speed measured from SODAR system was compared with existing models. Furthermore, the turbulence characteristics were analyzed and compared along with the turbulence intensity. From the economic point of view the SODAR system was found to be cost-effective at higher heights. The results of this study are expected to provide useful information for the deployment of remote sensing instruments for wind energy development in India.

Study of different parameters estimation methods of Weibull distribution to determine wind power density using ground based Doppler SODAR instrument

The effectiveness of nine different numerical methods is examined for calculating the parameters of Weibull distribution at three different heights 80m, 100m and 120m to estimate wind power density. The measurement campaign was conducted at Kayathar, Tamil Nadu, India. The time series wind data were recorded using SecondWind Triton SODAR (Sound Detection and Ranging) instrument. Firstly, the fidelity assessment of SODAR measurement was examined. The aim of this study is to identify the more accurate method for computing wind power density of a selected region. The performance of the selected methods is judged based on goodness of fit test i.e. Root Mean Square Error Test (RMSE), Coefficient of Determination (R2), Mean Absolute Percentage Error (MAPE), and Chi-square Test (X2). Wind power densities are estimated with the help of estimated parameter values. This study proposes an approach to utilize SODAR and also aims to examine the accuracy of SODAR measurement by comparing the results with cup anemometer, in an attempt to establish adequate criteria for an effective utilization of SODAR for wind resource assessment. The results suggest that SODAR may be used asan alternative to meteorological mast.

Comparative analysis of Weibull parameters for wind data measured from met-mast and remote sensing techniques

The remote sensing techniques are gaining attention worldwide for the comprehensive assessment of wind resource in flat, complex, and mountainous terrain. This paper presents an attempt to increase the confidence on remote sensing technique to compute Weibull parameters at higher heights for assessment of wind energy resource. The measurement campaign was conducted at Kayathar, Tamil Nadu, India. The 10 min average time series wind speed data for the period of one month (September 2014) were recorded simultaneously at 80 m and 100 m using cup anemometer installed in the proximity of 120 m meteorological mast, Second Wind Triton SODAR (Sound Detection and Ranging) and Continuous-wave wind LIDAR (Light Detection and Ranging). The data obtained from this measurement were analyzed and Weibull parameters were evaluated using nine different methods. The applicability of nine methods for calculation of Weibull parameters is analyzed based on statistical analysis i.e. Root Mean Square Error Test, Coefficient of Determination, Mean Absolute Percentage Error, and Chi-square Test for both measuring techniques. This study also shows the performance of remote sensing technology by comparing with result obtained from met mast. The outcome of this study is expected to encourage the deployment of remote sensing techniques at Indian sites.

SODAR pattern classification and its dependence on meteorological parameters over a semiarid region of India

ABSTRACTThe variability of the atmospheric boundary layer together with meteorological parameters has been investigated over the semi-arid region Delhi. Two sources of the dataset have been used: sound detection and ranging (SODAR) and automatic weather station during the period from December 2013 to November 2014. A Laboratory Virtual Instrument Engineering Workbench (LabVIEW)-based programme has been developed to plot the stability class from A to F directly from the mixing height dataset. Based on the SODAR echograms and mixing height, temporal and seasonal variability of stability classes has been estimated. It is observed that the convective boundary layer height advances and decreases during the daytime depending on the increase and decrease of surface temperature due to solar heating of the ground. From seasonal classification of the stability class, it is observed that the class A and class E are dominated in convection and nocturnal periods in all seasons, whereas class F is not found during the winter and pre-monsoon seasons. Impact of meteorological parameters, that is, wind speed, temperature, and relative humidity on mixing height during different seasons has also been studied.

Experimental and numerical studies on the wake behavior of a horizontal axis wind turbine

The wake characteristics of a horizontal axis wind turbine have been investigated, both experimentally and numerically. The computational numerical solution was carried out for the full rotor model, using a Navier–Stokes solver, employing the k–ε model appropriately modified for the atmospheric flows. The experiments were conducted at a 2MW wind turbine for the measurements of upstream wind speed profiles, using SOund Detection and Ranging (SODAR), and wake wind speed profiles using Light Detection and Ranging (LIDAR), at varying distances between 2 and 7 times the rotor diameters downstream of the wind turbine. The evaluation of the computational model is made by comparing the predicted and measured velocities at the prescribed downstream locations at different upstream wind speeds. The present numerical setup employing the k–ε model and the fully mesh resolved rotor shows good agreement with the measurements. The model is used to find the relation between the wind speed and the wake recovery.

SODAR observations of inertia‐gravity waves in the atmospheric boundary layer during the passage of tropical cyclone

AbstractThis study reports characteristics of inertia‐gravity waves (IGWs) in the atmospheric boundary layer during the passage of Tropical Cylone‐03B, using the Doppler Sound Detection and Ranging (SODAR) observations at the Indian tropical station of Gadanki (13.45°N, 79.2°E; near the east coast of India). Wavelet analysis of horizontal winds indicates significant wave motion (˜60 h) near the characteristic inertial period. The hodograph analysis of the filtered winds shows an anti‐cyclonic turning of horizontal wind with height and time, indicating the presence of IGW. This study finds important implications in boundary layer dynamics during the passage of tropical cyclones.

Boundary layer jet on the lee side of Western Ghats during southwest monsoon as revealed by high resolution sodar winds

High resolution winds measured by SOund Detection And Ranging (SODAR) in the atmospheric boundary layer (ABL) over Pune, located on the lee side of the Western Ghats (WG) reveal the presence of Low Level Jet (LLJ) in the atmospheric boundary layer (hereafter called as boundary layer jet, BLJ) during southwest monsoon (June–August) for three consecutive years, viz., 2009, 2010 and 2011. Its prevalence only during the monsoon period, even at monthly scale indicates a possible interconnection to another LLJ, Somali jet, present during this period. An investigation is done to look into the dominant mechanisms those could result in such an occurrence in the lee side of the WG. Baroclinicity, inertial oscillation, upstream topographic blocking and variability of Somali jet are the mechanisms considered. Baroclinicity due to east–west temperature gradient on the leeside to induce thermal wind and inertial oscillation appear to have a little role in LLJ formation. However, Somali jet seems to govern the BLJ on the lee side through its dynamical interaction with the WG causing flow reversal and wave breaking above WG and inducing acceleration of downslope winds. The height and sharpness of Somali jet core on the windward side and its magnitude as well as direction with respect to WG are observed to determine the strength of BLJ on the lee side illustrating the signature of the summer monsoon in the boundary layer over Pune.

Studies on Meteorological Parameters and Mixing Height in Gold Mining Area

Gold mining at Kolar Gold Fields is closed but some industries in this area are in operation and some may like to be established. Data on atmospheric and meteorological parameters were generated using SODAR (Sound Detection and Ranging) and automatic weather station in different seasons. Over 2000 sodar echograms were recorded and classified into six categories like rising layer, thermal plume (free), ground based layer (spiky top), ground based layer (flat top), ground based multiple layers and dot echo structures. Using echograms, unstable period was determined to know the diluting capability of atmosphere for pollutants in the seasons. The highest duration of mixing heights revealed the period of highest dispersion. Based on the sodar echograms and mixing height, stability classes for the different times of the day were evaluated, which can be used for the estimation of dispersion coefficients. Influence of wind speed, wind direction, temperature, humidity, solar radiation and rainfall on mixing heights was studied. Statistical model was developed for the prediction of mixing height. Model adequacy was checked using F-statistics, normal distribution curve and correlation between predicted and measured values of mixing heights.

INVESTIGATION OF POWER LAW WIND EXPONENT WITHIN THE LOWER BOUNDARY LAYER AT ILE-IFE, NIGERIA.

A sound detection and ranging (SODAR) equipment installed on the roof of a two-storey building at the Department of Physics, Obafemi Awolowo University Ile-Ife, Nigeria (7.52 0 N and 4.52 0 E), 294 m height above mean sea level and about 20 m above the ground level has been used to study on continuous basis the planetary boundary layer (PBL) wind. Eighteen thousand (18000) sets of hourly averaged data for the wind speed from 30 m above the surface to 500 m height at 20 m intervals had been used to study the power law wind exponent α over Ile-Ife Nigeria. The data covered about two and half years (from June 2009 to December 2011). Exponent α was found to increase with height and decrease with surface wind speed. It was also discovered that α had both diurnal and seasonal variations. The values at daytime were lower than at nighttime and the wet months had higher values than the dry months. Its average for the dry months was 0.33 while the average for the wet months was 0.45.

Study on deep inland penetration of sea breeze over complex terrain in the tropics

Characteristics of sea breeze circulations over a tropical Indian station have been studied, based on one year of observations, by Doppler Sound Detection and Ranging (SODAR) system at National Atmospheric Research Laboratory, Gadanki (13.5°N, 79.2°E), India. The effect of sea breeze circulations on the dynamics of low level flow patterns in atmospheric boundary layer over complex terrain in tropics is investigated. The study reveals that a sea-breeze front develops well along the eastern coastal plain of southern peninsular India and propagates over inland up to the distance about 80km. It is found that the sea-breeze signal is well recognized during the months of February, March and April due to the presence of tropical easterlies. In these three months, SODAR observations indicate a late afternoon intensification of sea-breeze flow in the height range 0.2–0.6km during 1400 and 2000 local time (LT). The decrease in temperature of 2°C and increase in relative humidity of 20% at surface level are observed on a sea breeze day as compared to a non-sea breeze day. Sea-breeze inland propagation is absent for the rest of the months due to the opposing meso-flow direction. ERA-Interim reanalysis U-velocity data over south-Asia grid also corroborates the deep-inland penetrations of sea breeze circulations over this site.

Assessing atmospheric stability and its impacts on rotor‐disk wind characteristics at an onshore wind farm

ABSTRACTAs the average hub height and blade diameter of new wind turbine installations continue to increase, turbines typically encounter higher wind speeds, which enable them to extract large amounts of energy, but they also face challenges due to the complex nature of wind flow and turbulence in the planetary boundary layer (PBL). Wind speed and turbulence can vary greatly across a turbine's rotor disk; this variability is partially due to whether the PBL is stable, neutral or convective. To assess the influence of stability on these wind characteristics, we utilize a unique data set including observations from two meteorological towers, a surface flux tower and high‐resolution remote‐sensing sound detection and ranging (SODAR) instrument. We compare several approaches to defining atmospheric stability to the Obukhov length (L). Typical wind farm observations only allow for the calculation of a wind shear exponent (α) or horizontal turbulence intensity (IU) from cup anemometers, whereas SODAR gives measurements at multiple heights in the rotor disk of turbulence intensity (I) in the latitudinal (Iu), longitudinal (Iv) and vertical (Iw) directions and turbulence kinetic energy (TKE). Two methods for calculating horizontal Ifrom SODAR data are discussed. SODAR stability parameters are in high agreement with the more physically robust L,with TKE exhibiting the best agreement, and show promise for accurate characterizations of stability. Vertical profiles of wind speed and turbulence, which likely affect turbine power performance, are highly correlated with stability regime. At this wind farm, disregarding stability leads to over‐assessments of the wind resource during convective conditions and under‐assessments during stable conditions. Copyright © 2011 John Wiley & Sons, Ltd.