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Verner E. Suomi, Kirby J. Hanson, and Robert J. Parent

Abstract

This paper reports on a digital measurement (“chirp”) system which has application for a wide range of meteorological and earth satellite measurements.

The system employs a simple concept in which a voltage pulse, proportional to a sensor voltage, is used to generate a burst of pulses from a voltage controlled oscillator (VCO). A count of the high frequency oscillations which make up the “chirp” provides the digital measurement. The system is adapted to multiple sensor use with a multiplexer.

The system has the advantage in that one has the option of selecting an ac amplifier for low level signals in conjunction with a variety of multiplexers and VCO for the desired measurement. One particular combination of multiplexer and VCO was used to demonstrate its use as a digital radiosonde.

A flight test of the digital radiosonde was obtained. Results clearly show fine structural detail in the temperature profile without any need for subjective interpretation by the operator. Numerous isothermal and inversion layers less than 100 m in thickness were observed.

The digital radiosonde used conventional (U.S. Weather Bureau) temperature and humidity sensors. Temperature resolution is about 0.1C and relative humidity is about 0.1 per cent. The system resolution is 0.1 per cent.

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Stephen K. Cox, James A. Maynard, and Verner E. Suomi

Abstract

An analysis of tropical radiosonde temperature measurements made during the Line Island Experiment suggests that conventional radiosonde preflight procedures are inadequate in a remote tropical environment. Temperatures computed from conventional and modified baseline techniques are compared at five pressure surfaces, 1000, 800, 600, 400 and 200 mb. Temperatures obtained from the two baseline techniques showed an average deviation at 1000 mb of 0.96C for 62 soundings. These comparisons indicate that a careful examination of radiosonde calibration techniques is needed before large investments are made in future global experiments.

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Dennis R. Phillips, Eric A. Smith, and Verner E. Suomi

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Earl G. Droessler, Wallace E. Howell, Verner E. Suomi, and Helmut Weickmann
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KIRBY J. HANSON, THOMAS H. VONDER HAAR, and VERNER E. SUOMI

Abstract

This study describes a method for determining the reflection of sunlight to space and absorption by the earth and atmosphere, using low-resolution radiometer data from earth satellites. The method has been used with TIROS IV data together with radiation measurements at the ground to determine the reflection and absorption of sunlight over the United States during the spring of 1962.

The results indicate that for this region and time, 40 percent of the incident sunlight at the top of the atmosphere was reflected to space, 13 percent was absorbed by the atmosphere and clouds, and the remaining 47 percent was absorbed at the earth's surface. Atmospheric absorption of sunlight varied from over 20 percent in the moist air in southeastern United States to less than 10 percent over much of the dry mountainous west and northern plains.

When atmospheric absorption values determined from this study are compared with earlier studies of absorption in a cloudless atmosphere, there is good agreement at low values of atmospheric water vapor; however, the present study gives significantly higher absorption at high values of water vapor.

Based on this study, an empirical relationship is determined for fractional absorption of sunlight in an atmosphere with clouds as a function of optical pathlength of water vapor: qa=0.096+0.045(u*)½logeu*. The fractional absorption of sunlight, qa, is the fraction of the total amount incident at the top of the atmosphere. The optical pathlength, u*, is given in cm.: u*=u.sec ζ. Here, u is total precipitable water in a vertical column, given in cm., and ζ is the solar zenith angle.

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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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James R. Greaves, Geoffrey DiMego, William L. Smith, and Verner E. Suomi
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