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James F. Morrissey and Frederick J. Brousaides

Abstract

Temperature-induced humidity errors in the carbon humidity element ML-476 are described. The dominant error is caused by solar irradiation and results in a lowering of reported humidity values. The effect was found with both the military AN/AMT-12 and weather Bureau radiosondes. Flight studies indicate that a significant improvement in data acquisition will result from a blackening of the sensor channel walls.

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James F. Morrissey and Andrew S. Carten Jr.

A description is given of the original rocketsonde thermistor mount, consisting of a 10-mil bead suspended between two metal posts. The difficulties encountered with this mount and the subsequent development of the superior “thin-film” mount are also described. The uncertainties associated with the use of the latter mount are outlined along with their effect on data acceptance.

A different approach to the original problem is described, which employs longer leads for dissipation of heat conducted to the bead. The uncertainty associated with the long lead is shown to be minimal. Preliminary results of a series of 10 rocket flights are presented. These results tend to confirm the advantages of the long lead mount.

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Frederick J. Brousaides and James F. Morrissey

Abstract

Efforts are described involving the development of an expendable, balloon-borne dew point hygrometer which is compatible with standard radiosonde equipment, maintains the inherent accuracy of this sensing technique, and as far as is possible reduces the cost. Presented here are both laboratory and field test data on a selected number of flights, together with a description of the device and its operation.

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Frederick J. Brousaides and James F. Morrissey

A modification to the radiosonde humidity channel to eliminate a temperature induced bias is described. Data are presented from flight test comparisons of radiosondes so modified and standard unmodified radiosondes. It is anticipated that the redesign of the current, standard radiosondes will reflect essentially the modifications described herein and consequently the data indicate the type and magnitude of change in the reported humidities which may be expected. The data are essentially in agreement with predicted changes from a previous paper (Morrissey and Brousaides, 1970). Further field testing of this and other modifications is proposed to determine residual error. Similar tests to standard instrumentation would permit corrections to archived data.

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James F. Morrissey and Frederick J. Brousaides

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Witold F. Krajewski, Mark L. Morrissey, James A. Smith, and David T. Rexroth

Abstract

A Monte Carlo simulation study is conducted to investigate the performance of the area-threshold method of estimating mean areas rainfall. The study uses a stochastic space-time model of rainfall as the true rainfall-field generator. Simple schemes of simulating radar observations of the simulated rainfall fields are employed. The schemes address both random and systematic components of the radar rainfall-estimation process. The results of the area-threshold method are compared to the results based on conventional averaging of radar-estimated point rainfall observations. The results demonstrate that when the exponent parameter in the ZR relationship has small uncertainty (about ±10%), the conventional method works better than the area-threshold method. When the errors are higher (±20%), the area-threshold method with optimum threshold in the 5–10 mm h−1 range performs best. For even higher errors in the ZR relationship, the area-threshold method with a low threshold provides the best performance.

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