Preliminary results of utilizing the high resolution FM radar as a boundary-layer probe

Bean, B. R.; McGavin, R. E.; Chadwick, R. B.; Warner, Brian D.

doi:10.1007/bf00184784

Cited by 27 publications

(12 citation statements)

References 6 publications

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“…(See the relevant discussion in Further support for our deduced refractivity fluctuations and reflectivity comes from the observations of Bean et al (1971), who measured the refractivity structure function at 20-cm spacing and found good agreement with the reflectivity measured with their FM-CW radar. Thus, while the present aircraft observations cannot resolve refractivity fluctuations at horizontal scales less than 0.5 m, there is direct though rare evidence of the existence of the required sub-meter scale perturbations.…”

Section: Radar Refleetivity Of a Turbulent Interfaeial Layer And Fosssupporting

confidence: 63%

Microscale ordered motions and atmospheric structure associated with thin echo layers in stably stratified zones

Metcalf

Atlas

1973

Boundary-Layer Meteorol

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Abstract. The interpretation of ultra-high resolution radar observations of thin clear-air echo strata is made with the aid of fine-scale aircraft measurements. The echo layer, generally comprising two sub-strata each 5 m thick and spaced 7-10 m apart, is found within a 10-20 m deep section of a strong inversion where the thermal stability and shear are maximized, and the Richardson number is close to 0.25. Mechanical turbulence is restricted entirely to this layer; the variance of the N-S velocity component, av 2, is the strongest, consistent with the orientation of the shear vector in this stratum. Spectra and cospectra of a 9-s slant run through the echo stratum show remarkably ordered motions. A strong negative peak of covariance at 80-m scale, accompanied by a zero of covariance and bulges in the longitudinal (v) and vertical (w) velocity spectra, is identified with breaking KelvinHelmholtz waves oriented in the N-S direction along the shear vector. A synthesis of the temperature and velocity structures from measurements along the flight path confirms the ordered motion deduced from the spectra and reveals a group of K-H waves of 80-m length and 10-m height at the height of the radar echo. Microscale K-H ripples of 3-4 m length are also deduced to be present in the 0.5 m thick interfacial region where the thermal gradient and shear are strongly enhanced by the larger shearing K-H wave.Two possible sources of the echoes are proposed: (1) scatter from fully developed turbulence within the interfacial zone in an inertial subrange falling entirely in sub-meter scales; and (2) the incoherent summation of specular reflections from properly oriented portions of the microscale K-H ripples. While the authors favor the first of these mechanisms, both require stringent conditions (rf the physical microstructure which are beyond the available observations. Fossil turbulence is precluded as an echo mechanism.

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Section: Radar Refleetivity Of a Turbulent Interfaeial Layer And Fosssupporting

confidence: 63%

Microscale ordered motions and atmospheric structure associated with thin echo layers in stably stratified zones

Metcalf

Atlas

1973

Boundary-Layer Meteorol

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“…The computed C~ values ranging from 10-13 to 10-12 m-2 / 3 seem to be on the high side. The values of C~ have been shown to be in the range 10-15 to 10-13 m-2 / 3 (Bean et al 1971;Sengupta et al 1987). This discrepancy may be due to the fact that the present measurements are for tropical latitudes.…”

Section: (A) Height Profiles Of C~mentioning

confidence: 99%

Measurements of the Radio Refractive Index Structure Parameter C2n with a Microwave Refractometer in Tropical Latitudes

Sarma¹,

Pasricha²

1989

Aust. J. Phys.

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The spatial and temporal variations of the radio refractive index lead to scattering of electromagnetic energy. Modern communication systems are subject to vagaries of the turbulence due to the radio refractive index fluctuations. Vertical resolution of radiosondes is insufficient to resolve the structures of clear air turbulence in the atmosphere. In a tropical country like India, aircraft measurements of radio refractive index fluctuations have been non-existent. Measurements on the fine structure information of radio refractivity have now been made at tropical latitudes, using an airborne microwave refractometer. The atmospheric turbulence structure parameter C~, deduced from such height profiles of radio refractivity, has a lower value in local winter than in summer. These values of C~ are large compared with the values obtained using routine radiosonde observations. Spectra of radio refractive index fluctuations at different heights and the scale size of the inhomogeneities have been estimated.

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“…In a previous study in eastern Colorado (Bean et al, 1971) the FM-CW radar returns were compared to refractivity measurements from a nearby tower. The structure function of refractive index is defined as It has been noted that the trade-wind inversion is characterized by a reversal in the gradient of the temperature as well as by a steep lapse rate of humidity.…”

Section: Resultsmentioning

confidence: 99%

“…The FM-CW radar was first used to study atmospheric structure in the San Diego area (Gossard and Richter, 1970) and was then used in eastern Colorado (Bean et al, 1971). Here, we report on a study of the Pacific trade-wind inversion in the area of the Hawaiian Islands.…”

Section: Introductionmentioning

confidence: 99%

A Note on the FM-CW radar as a remote probe of the pacific trade-wind inversion

Bean

McGavin

Warner

1973

Boundary-Layer Meteorol

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Abstract. A vertically pointed FM-CW radar was used to monitor the Pacific Trade-Wind Inversion in the Hawaiian Islands during the summer of 1971. An instrumented aircraft was used for in situ measurements of radio refractivity and temperature. The correspondence between the position of the radar returns and the aircraft data was excellent. The strong returns seen by the radar were due chiefly to the strong lapse of humidity across the inversion.The radar indicated that over the island of Lanai the trade-wind inversion was highly variable both in position and intensity. At times the layer would move from above 2 km to less than 1 km in the space of five minutes associated with strong mechanical turbulence. Its thickness would change rapidly from tens of meters to hundreds of meters. Wave-like structure induced by the mountains on the east side were observed by the radar.Our analysis indicates that interpretation of in situ aircraft measurements may be greatly aided by using the FM-CW radar as a guide.

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Preliminary results of utilizing the high resolution FM radar as a boundary-layer probe

Cited by 27 publications

References 6 publications

Microscale ordered motions and atmospheric structure associated with thin echo layers in stably stratified zones

Microscale ordered motions and atmospheric structure associated with thin echo layers in stably stratified zones

Measurements of the Radio Refractive Index Structure Parameter C2n with a Microwave Refractometer in Tropical Latitudes

A Note on the FM-CW radar as a remote probe of the pacific trade-wind inversion

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