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Nadav Levanon

Abstract

This work demonstrates the feasibility of determining the east-west component of the sea surface slope distribution from a synchronous satellite, through quantitative analysis of the sun glitter.

The Cox-Munk sun glitter technique, utilizing a single photograph of the whole-sun glitter pattern, taken from an aircraft altitude, is adapted to a much higher altitude. This is done by making a sequence of light intensity measurements, reflected from a single point on the ocean, as this fixed point scans the westward moving sun glitter pattern.

Wind velocity is calculated from the slope variance, using the Cox-Munk empirical relation. Calculated wind velocities for three locations in the Pacific, on two separate days, are compared to direct wind measurements taken at these locations during the Line Islands Experiment. The agreement is within ±1 m sec−1.

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Nadav Levanon and Yochanan Kushnir

Abstract

An approximate analytical solution of the vertical equation of motion for constant density superpressure balloons is obtained. It is shown how this solution can be used to filter out neutrally buoyant oscillations in balloon records.

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Nadav Levanon and Paul R. Julian

Abstract

Daily 150 mb maps south of 45°S were prepared for the period 16 November 1975–16 March 1976, using the extensive coverage of the TWERLE balloons in that area, in addition to the sparse radiosonde network. A sample of one daily map for each month, and five monthly average maps am given to demonstrate the technique and the potential information in the TWERLE data.

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Nadav Levanon and Michael A. Heinzelman

Abstract

A description is given of how the surplus bandwidth of the standard radiosonde can be used for an additional high-quality telemetry channel. Bounds imposed on the channel by the existing radiosonde signal are discussed, as well as an FM/FM subcarrier system which fits into these bounds. Also given are detailed circuit diagrams of the voltage-controlled oscillator added to the radiosonde, and the phase-locked loop used in the ground station.

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Nadav Levanon, Juris Afanasjevs, Robert A. Oehlkers, and Verner E. Suomi

Abstract

The pressure sensor for the Tropical Wind Energy conversion and Reference Level Experiment (TWERLE) is described. Key design features of the sensor are: capacitive coupling, reference at midrange, up-down counting, passive oven, storage at flight pressure and prelaunch calibration. Sensor specifications are given which are based on the production results of 440 units. Drift, as estimated from simulated life tests, is 1 mb per 6 months. The overall weight of the sensor, including thermal package, is 180 g.

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Nadav Levanon, Robert A. Oehlkers, Scott D. Ellington, William J. Massman, and Verner E. Suomi

Abstract

This paper presents measured data related to the question of how constant are “constant-level” balloons. The simultaneous use of two balloon-borne instruments, a radio altimeter and a pressure sensor, operating on entirely different principles, help to distinguish between sensor noise and true balloon altitude fluctuation. Four types of superpressure balloon altitude changes at the level of 150 mb were observed: (i) neutral buoyancy oscillations (NBO) with a period of about 200 sec and with peak-to-peak amplitude of up to 50 m, (ii) short-term oscillations with a period of ∼1.2 hr and peak-to-peak amplitudes of up to 80 m, (iii) diurnal half-cycle (day observations only) with an amplitude of up to 150 m, and (iv) possible trends of up to 120 m per day.

The data were obtained during four superpressure-balloon 150-mb flights in the Southern Hemisphere. These balloon flights were part of a test program for the TWERL Experiment. NCAR's GHOST balloons and navigation system were used, with the final version of the TWERLE radio altimeter and an early version of the pressure sensor.

The data are presented with a discussion of their limitations, mainly aliasing, ambiguity, and the absolute accuracy of the pressure sensor. A theoretical analysis of the NBO, with a spectrum analysis of supporting ground radar data, are given in the Appendix.

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