ASTM_D_7145_-_05_2015.pdf

Designation:D714505(Reapproved 2015)Standard Guide forMeasurement of Atmospheric Wind and Turbulence Profilesby Acoustic Means1This standard is issued under the fixed designation D7145;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide describes the application of acoustic remotesensing for measuring atmospheric wind and turbulence pro-files.It includes a summary of the fundamentals of atmosphericsound detection and ranging(sodar),a description of themethodology and equipment used for sodar applications,fac-tors to consider during site selection and equipmentinstallation,and recommended procedures for acquiring validand relevant data.1.2 This guide applies principally to pulsed monostaticsodar techniques as applied to wind and turbulence measure-ment in the open atmosphere,although many of the definitionsand principles are also applicable to bistatic configurations.This guide is not directly applicable to radio-acoustic soundingsystems(RASS),or tomographic methods.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisguide.2.Referenced Documents2.1 ASTM Standards:2D1356 Terminology Relating to Sampling and Analysis ofAtmospheres3.Terminology3.1 DefinitionsRefer to Terminology D1356 for generalterms and their definitions.3.2 Definitions of Terms Specific to This Standard:Note:The definitions below are presented in simplified,common,qualitative terms.Refer to noted references for moredetailed information.3.2.1 acoustic beam,nfocused or directed acoustic pulse(compression wave)propagating in a radial direction from itspoint of origin.3.2.2 acoustic power,nrelative amplitude or intensity(dB)of an atmospheric compression wave.3.2.3 acoustic refractive index,nratio of reference(at astandard temperature of 293.15 K and 1013.25 hPa pressure)speed of sound value to its actual value.3.2.4 acoustic scatter,nthe dispersal by reflection,refraction,or diffraction of acoustic energy in the atmosphere.3.2.5 acoustic scattering Cross-section Per Unit Volume(,m1),nfraction of incident power at the transmit frequencythat is backscattered per unit distance into a unit solid angle.3.2.6 acoustic attenuation(,dB/100m),nloss of acous-tic power(acoustic wave amplitude)by beam spreading,scattering,and absorption as the transmitted wavefront propa-gates through the atmosphere.3.2.7 backscatter,npower returned towards a receivingantenna.3.2.8 beamwidth(degrees),none way angular width(halfangle at 3dB)of an acoustic beam from its centerlinemaximum to the point at the beam periphery where the powerlevel is half(3 decibels below)centerline beam power.3.2.9 bistatic,adjsodar configuration that uses spatiallyseparated antennas for signal transmission and reception.3.2.10 clutter,nundesirable returns,particularly fromsidelobes,that increase background noise and obscure desiredsignals.3.2.11 decibel(dB),nlogarithmic(base 10)ratio of powerto a reference power,usually one-tenth bell;for power P1 andreference power P2,the ratio is given by 10log10(P1/P2).3.2.12 directivity,nconcentration of transmitted power(dB)within a narrow beam by an antenna,measured as a ratioof power in the main beam to power radiated in all directions.3.2.13 Doppler frequency(fD,Hz),nshifted frequencymeasured at the receiver from the scattered acoustic signal.3.2.14 effective antenna aperture(Ae,m2),nproduct ofantenna area with antenna efficiency.1This guide is under the jurisdiction of ASTM Committee D22 on Air Qualityand is the direct responsibility of Subcommittee D22.11 on Meteorology.Current edition approved April 1,2015.Published April 2015.Originallyapproved in 2005.Last previous edition approved in 2010 as D7145 05(2010)1.DOI:10.1520/D7145-05R15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.2.15 gain(G),nincrease in power(dB)per unit areaarising from the product of antenna directivity with efficiency.nnon-dimensional effective aperture amplification factorarising from an antennas directivity.3.2.16 inter pulse period(tmax,s),ntime between the startof successive transmitted pulses or pulse sequences.3.2.16.1 DiscussionThe inter pulse period(IPP)is theinverse of the pulse repetition frequency(PRF)in Hertz(Hz).3.2.17 monostatic,adjsodar configuration that uses thesame antenna for transmission and reception.3.2.18 Neper,nnatural logarithm of the ratio of reflectedto incident sound energy flux density at a given range.3.2.19 pulse,nfinite burst of transmi