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J. Owen

Abstract

A study designed to point out the effect of the frequently sharp CT-MT boundary, herein called the “dry line,” on thunderstorm development was undertaken using synoptic surface charts, upper air soundings, 500-mb charts, 700-mb charts, and hourly radar summaries for the spring months of April-June from 1959 through 1962. Plots of new radar echo area formation versus distance from the surface dry line were made for all days on which the dry line was discernible, and it was found that the immediate vicinity of the dry line is indeed a highly preferred thunderstorm developmental zone. Activity also was found to develop carrier and organize more frequently into line formation along the dry line than at locations further removed. 500-mb supporting features were found present in a majority of cases.

When equal amounts of moist and dry air were mixed, thunderstorm formation appeared feasible in all cases, even without the aid of convergence between moist and dry air. Essentially the same was true, however, for the unmixed moist air in the first 50 mi east of the dry line.

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J. S. OWENS

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No Abstract Available.

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J. Owen Rhea

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A. J. Hermann and W. B. Owens

Abstract

The rates of energy flux out of newly formed circular patches of dense water (chimneys) are considered as a function of patch size on an f plane. The dense fluid resulting from a rapid deep convective process serves as a powerful reservoir of both mass and energy. Energy flux due to superinertial waves precedes mass flux. Both mass and energy are ultimately carried away from the local site of convection through baroclinic instability. Analytical and numerical methods are employed to investigate the relative amounts of potential energy radiated to the far field by either process and the rates at which this is accomplished. An analytical solution is developed for the superinertial transients generated during linear, axisymmetric gravitational adjustment of a unit step. Initial energy decay by axisymmetric gravitational collapse is greater for a narrow chimney than for a wide one, but ultimately this is equated and surpassed by the steady spreading of the wide chimney via its baroclinic breakup into smaller structures.

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Owen E. Thompson and Richard J. Wolski

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This study deals with atmospheric tropopause detection by satellite. It is found that incorrect forecasting of the tropopause height yields a systematic bias in temperature profile estimates which use an algorithm (specifically, the “minimum information” method) operating on satellite-measured spectral infrared radiances and forecast temperature profiles as first guess fields. This bias follows from the general inability of linear satellite-based temperature retrieval schemes to substantially correct “shape” errors in the first guess field, owing to the rather low vertical resolving power of such schemes. A non-linear approach to tropopause detection which makes use of certain selected ratios of measured spectral radiances is shown to have some power for correcting these biases.

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Farn P. Parungo and J. Owen Rhea

Abstract

A procedure is presented for identifying those silver iodide particles in ice crystals that have behaved as snow crystal nuclei. The new technique is based on the principle that any submicron particle can act as a nucleus in its own superstaurated solution, and can grow to any desired crystal size (the final size depending on time of exposure to the supersaturated solution). For the procedure presented here, an aqueous solution of 30% potassium iodide supersaturated with silver iodide is used.

Application of the technique in a weather modification field research project is described. A case-study example is presented, and results of the season's experiments are discussed with emphasis on contributions of the nuclei identification data. It is concluded that the technique has considerable practical utility in qualitative determination of effects from cloud seeding.

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J. A. Owen and T. N. Palmer

Abstract

Two ensembles of 90-day forecasts for 1982–83 have been made with the UK Meteorological Office 11-layer atmospheric general circulation model. Each ensemble comprised three integrations initialized one day apart, using analyses from December 1982. The first ensemble used observed SSTs and the second used climatological SSTs. Our objectives were to compare the skill of the two ensembles and to compare the results with a longer climate sensitivity experiment.

The skill of the forecasts for 10-, 30- and 90-day means was assessed using root-mean-square wind errors at 200 mb. In the tropics, the skill was improved with observed SSTs on all time scales. In the extratropics, the skill was improved on the 30-day time scale except at the initial stages of the forecasts, and the skill was also improved for 90-day means. On the 10-day time scale, however, the improvement was not consistent, and there were periods in which the errors were larger with observed SSTs. The response of the model to the observed SSTs was found to be similar to that of a 540-day perpetual January integration with the winter mean SST anomaly for 1982–83.

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William J. Schmitz Jr. and W. Brechner Owens

Abstract

It is demonstrated that the outcome of an intercomparison between data and the vertical distribution of eddy kinetic energy predicted by a previously developed numerical model of the MODE area is frequency dependent. In the range of periods from 50 to 150 or even to 400 days (one definition of the temporal mesoscale, the scale that the model was designed to simulate), the comparison is quite good. For periods in the range of 5 to 50 days, the agreement is poor. For periods longer than 400 days, the comparison is indeterminate. Earlier conclusions concerning the relation of model results to the MODE data should be qualified by stipulating frequency range, and future intercomparisons for any model in all regions should be conscious of the desirability of doing so across common frequencies.

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Peter J. Gierasch and Owen B. Toon

Abstract

If Mars has permanent CO2 polar caps, atmospheric heat transport may cause the atmospheric pressure to be extremely sensitive to variations of solar heating at the poles. This could happen because atmospheric heating depends on density, which depends strongly on the polar temperature through the vapor pressure relation. A simple climatological model is used to study the question.

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Farn P. Parungo and J. Owen Rhea

Abstract

Results from measurements made to study the behavior of lead aerosols in Denver urban air as latent ice nuclei are discussed.

In the study, use was made of three independent measuring systems. These were: 1) an NCAR continuous ice nucleus counter with a capability to convert suspended lead compounds to lead iodide particles prior to passage through the cloud chamber and counting unit, 2) an atomic absorption spectrophotometer for analysis of lead content in collected air and rain water samples, and 3) the use of Tufts’ spot test for obtaining lead particle concentration and size distribution from collected Millipore filters. Both ground and airborne measurements were made.

Pertinent findings included: 1) good Qualitative agreement among the three types of measurements; 2) lead content of rain water an order of magnitude greater than silver concentration in seeded snow samples which were collected in a weather modification seeding target area using silver iodide as the seeding agent; and 3) 10-300 lead particles (latent ice nuclei) liter−1 existing up to 9000 ft above the surface when unstable temperature stratification existed and which were converted into active ice nuclei (lead iodide particles) when passed through an iodine vapor chamber.

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