Papers by Vim Toutenhoofd
Monthly Weather Review, Mar 1, 1983
Abstract Observations are described of a small, isolated cumulonimbus developing in a wind field ... more Abstract Observations are described of a small, isolated cumulonimbus developing in a wind field with relatively little directional shear. The storm displayed a high degree of symmetry about a vertical plane through the center of the storm oriented parallel to the wind shear vector. Single-Doppler observations of this storm reveal a region in which the horizontal component of the wind vector was opposite to that of the mid-level environmental wind, suggesting the presence of a vortex pair circulation. The storm was simulated with a three-dimensional cloud model which reproduced these and some of the other observed storm characteristics. The environmental wind shear in which the storm developed is similar to that of the composite sounding documented by Fankhauser and Mohr (1977) for weak, isolated or scattered storms in northeast Colorado. Therefore, this symmetric structure, involving two counter-rotating vortices, may be a common feature of isolated storms in this area.
Journal of applied meteorology, Mar 1, 1976
Journal of the Atmospheric Sciences, Nov 1, 1974
Clear Air Turbulence and Its Detection, 1969
The National Center for Atmospheric Research has, for the last two winters, undertaken investigat... more The National Center for Atmospheric Research has, for the last two winters, undertaken investigations of lee waves and orographic wind phenomena in the Front Range of the Rocky Mountains near Boulder, Colorado. During February 1968 the observational program was conducted in cooperation with the Air Force HI-CAT Program, the Canadian National Research Council, ESSA, The Explorer’s Research Corporation and the White Sands Missile Range. All of these agencies contributed aircraft and personnel for operation of a joint flight program aimed at obtaining, for the first time, synchronous quantitative data on lee waves and associated turbulence phenomena from the surface to 70,000 feet above representative Rocky Mountain topography. To an extent the program was successful, in that several cases of moderate amplitude lee waves were observed with 3 or 4 aircraft. Two of these have been partially analyzed and some results are presented. The most significant result of the 1968 program was the large amplitude of both standing gravity waves and turbulence in the stratospheric levels sampled by the HI-CAT U-2. No complete explanation of these effects is offered, but a relation recently proposed by Scorer appears relevant.
Journal of Applied Meteorology, 1976
Experiments have been conducted to determine the effects, within cumulus clouds, of seeding with ... more Experiments have been conducted to determine the effects, within cumulus clouds, of seeding with silver iodide; such effects are determined by correlating the presence of ice particles with the presence of silver iodide. This correlation is made possible by the use of a sailplane, which has the capability of remaining in the cloud updraft and the seeded plume for relatively long periods of time. The correlation method provided a very sensitive test for distinguishing seeding effects from natural ice development. Case studies using this technique are discussed. Measurements in one small cloud having a base at −12°C showed concentrations at −15°C in the plume of up to 400 ice crystals per liter about 4 min after seeding. Aggregation of stellar dendrites occurred for particles as small as 400–500 μm diameter and about half of the available crystals were in aggregates after about 15 min. The output efficiency of the TB-1 pyrotechnic flares used in the experiment is estimated to be at le...
Journal of Applied Meteorology, 1974
Monthly Weather Review, 1983
Journal of the Atmospheric Sciences, 1974
Journal of the Atmospheric Sciences, Nov 1, 1974
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Papers by Vim Toutenhoofd