This study investigates subtle variations of the zenith and azimuth dependence of VHF‐radar echo power in the troposphere and lower stratosphere. Using the middle and upper atmosphere (MU) and Aberystwyth radars, we reanalyze data from two areas of the literature on tilted aspect‐sensitive scatterers, linking results from the spatial interferometry (SI) and Doppler beam‐swinging (DBS) techniques. Whereas wind profilers commonly use three or five radar beams, we examine a MU radar data set with 64 beam positions, so that maps of echo power distribution can be plotted as far as 5° from zenith. The power distribution pattern is often skewed, with the azimuth of maximum power being closely related to the wind shear caused by, for example, inertia‐gravity waves in the lower stratosphere. The results imply that inertia‐gravity wave motions are closely coupled to the smaller‐scale wind field, causing patches of Kelvin‐Helmholtz instability and/or steepening of other shorter‐period gravity waves. These effects can alter the distribution of the tilts of aspect‐sensitive scatterers and explain the skewed echo power patterns. The deviations of vertical‐beam incidence angle measured by SI are found to be inappropriate for off‐vertical beams, and it also appears impossible for basic DBS systems to be used for measuring vertical‐beam incidence angles. Further tests of mountain wave data are consistent with the tilted layer model and help to confirm that the azimuth of gravity waves may be calculated using radar echo‐power imbalances.
Summary This study reports the findings of a regional investigation of fault seal prediction and production behaviour including several fields in the Halten Terrace area, on the Norwegian Continental Shelf. The Upper Jurassic quartz rich, shallow marine deposits of the Garn Fm are investigated. Faults where Garn Fm. is self-juxtaposed are considered and in short; the study compares production data (fault properties from dynamic flow history matching), 4D and initial pressure data) with fault permeability predictions from a combination of SGR calculations and petrophysical measurement of cored faults. One field also give a calibration point for smearing potential of the shale below the Garn Fm as the faults in this field only provide very limited communication across the shale even if Garn Fm is juxtaposed against deeper stratigraphy.
Recent radar observations of mountain waves in the troposphere and lower stratosphere above Aberystwyth (52.4°N, 4.0°W) indicate that, on average, the wave alignment is related more closely to the wind direction within the boundary layer than to the alignment of mountain ridges. This is investigated using independent data NOAA AVHRR imagery of both mountain-wave clouds and convective cloud streets, combined with surface synoptic wind measurements. The mountain-wave cloud bands are found to be aligned not at exactly 90° to the surface wind but rotated a further 18° clockwise. Similarly, in an important backup test, the cloud streets are found not to be parallel to the surface wind but rotated 12° clockwise, which agrees with over 30 years of observations, most recently of wind rows on the ocean by synthetic aperture radar (SAR). Because the wind rotates, on average, clockwise with increasing height in the northernhemisphere boundary layer, the mountain-wave clouds will be at 90° to the wind direction in the middle of the boundary layer. Therefore, the satellite images independently confirm earlier mesosphere-stratosphere-troposphere (MST) radar observations. Mountain lee waves may corrupt SAR measurements of surface wind above the ocean, so knowledge of their alignment is useful; two examples of lee waves modulating the sea roughness west of Aberystwyth are discussed.
VHF atmospheric radar is used to measure the wind velocity and radar echo power related to long-period wind perturbations, including gravity waves, which are observed commonly in the lower stratosphere and tropopause region, and sometimes in the troposphere. These wind structures have been identified previously as either inertia-gravity waves, often associated with jet streams, or mountain waves. At heights of peak wind shear, imbalances are found between the echo powers of a symmetric pair of radar beams, which are expected to be equal. The largest of these power differences are found for conditions of simultaneous high wind shear and high aspect sensitivity. It is suggested that the effect might arise from tilted specular reflectors or anisotropic turbulent scatterers, a result of, for example, Kelvin-Helmholtz instabilities generated by the strong wind shears. This radar power-difference effect could offer information about the onset of saturation in long-period waves, and the formation of thin layers of turbulence.
Abstract. Fallstreak cirrus clouds are associated with super-saturated air, together with waves, instabilities and/or turbulence; however, their precise cause is usually uncertain. This paper uses already-published satellite, radiosonde and radar data, reanalysed to study some large fallstreaks which had been previously overlooked. The fallstreaks – up to 60 km long with a parent cloud 20 km wide – are caused by lifting and/or turbulence from a mountain wave, rather than, for example, Kelvin-Helmholtz instabilities. If turbulent breaking of mountain waves affects ice particle formation, this may be relevant for the seeder-feeder effect on orographic rain, and the efficiency of mountain-wave polar stratospheric clouds for ozone depletion.Key words. Meteorology and atmospheric dynamics (turbulence; waves and tides) – Atmospheric composition and structure (cloud physics and chemistry)
Abstract. Using the MU radar at Shigaraki, Japan (34.85°N, 136.10°E), we measure the power distribution pattern of VHF radar echoes from the mid-troposphere. The large number of radar beam-pointing directions (320) allows the mapping of echo power from 0° to 40° from zenith, and also the dependence on azimuth, which has not been achieved before at VHF wavelengths. The results show how vertical shear of the horizontal wind is associated with a definite skewing of the VHF echo power distribution, for beam angles as far as 30° or more from zenith, so that aspect sensitivity cannot be assumed negligible at any beam-pointing angle that most existing VHF radars are able to use. Consequently, the use of VHF echo power to calculate intensity of atmospheric turbulence, which assumes only isotropic backscatter at large beam zenith angles, will sometimes not be valid.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; instruments and techniques)
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3cuse xlink:href='%23a' transform='rotate(72 0 0)'/%3e%3cuse xlink:href='%23a' transform='rotate(-72 0 0)'/%3e%3cuse xlink:href='%23a' transform='scale(-1 1) rotate(72)'/%3e%3c/g%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h1200v600H0z'/%3e%3cpath stroke='%23FFF' stroke-width='60' d='m0 0 600 300M0 300 600 0' clip-path='url(%23b)'/%3e%3cpath stroke='%23C8102E' stroke-width='40' d='m0 0 600 300M0 300 600 0' clip-path='url(%23c)'/%3e%3cpath stroke='%23FFF' stroke-width='100' d='M300 0v300M0 150h600' clip-path='url(%23b)'/%3e%3cpath stroke='%23C8102E' stroke-width='60' d='M300 0v300M0 150h600' clip-path='url(%23b)'/%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='matrix(45.4 0 0 45.4 900 120)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='matrix(30 0 0 30 900 120)'/%3e%3cg transform='rotate(82 900 240)'%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='rotate(-82 519.022 -457.666) scale(40.4)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='rotate(-82 519.022 -457.666) scale(25)'/%3e%3c/g%3e%3cg transform='rotate(82 900 240)'%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='rotate(-82 668.57 -327.666) scale(45.4)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='rotate(-82 668.57 -327.666) scale(30)'/%3e%3c/g%3e%3cuse xlink:href='%23d' fill='%23FFF' transform='matrix(50.4 0 0 50.4 900 480)'/%3e%3cuse xlink:href='%23d' fill='%23C8102E' transform='matrix(35 0 0 35 900 480)'/%3e%3c/svg%3e)
