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M. T. Decker, F. Einaudi, and J. J. Finnigan

Abstract

During the 1978 PHOENIX experiment at the Boulder Atmospheric Observatory in Colorado, the presence of atmospheric gravity waves was detected by various independent remote sensing instruments. Fluctuations in the zenith atmospheric radiation were measured at 22.235 and 55.45 GHz in the water vapor and oxygen absorption bands and compared with corresponding fluctuations of surface pressure and the height of FM-CW radar echo returns. These fluctuations are explained, qualitatively and quantitatively, in terms of an internal gravity wave generated by wind shear above the boundary layer. The analysis shows that the oscillations at 22.235 GHz are essentially due to fluctuations of water vapor in the antenna beam while those at 55.45 GHz are due to temperature variations.

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S. J. Caplan, A. J. Bedard Jr., and M. T. Decker

Abstract

This study validates the predicted association between frequency of dry microburst occurrence and large temperature lapse rate. In applying lapse rate trend data and high time resolution data from remote sensors, we first compared lapse rates from the Denver rawinsonde with the thermodynamic profiler and obtained linear correlation coefficients ranging from .63 to .94. Continuous 20-minute radiometer samples of lapse rate were available throughout the experiment period. The data indicate a critical value of 700–500 mb lapse rate ≥8°C km−1 for dry microburst occurrence. Also, we found dry microburst occurrence in the Denver area better correlated with late afternoon lapse rates than with early morning lapse rates: 67% of dry microbursts occurred with 1200 UTC lapse rates ≥8°C km−1, while 89% of dry microbursts occurred with 2200 UTC lapse rates ≥8°C km−1. We recommend that remote sensor temperature retrievals such as with Radio Acoustic Sounding Systems (RASS) extend to at least 3 km AGL to aid dry microburst nowcasting and forecast verification.

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M. T. Decker, E. R. Westwater, and F. O. Guiraud

Abstract

Profiles of atmospheric temperature and water vapor derived from ground-based microwave radiometric measurements are compared with concurrent rawinsonde profiles including both clear and cloudy cases. Accuracies of the temperature profiles including the cloudy cases are quite close to predicted accuracies. Mean virtual temperatures between commonly used pressure levels are also compared and resulting rms accuracies are 1.1, 1.6, 2.0 and 2.8°C for the 1000–850, 850–700, 700–500 and 500–300 mb layers, respectively. The microwave technique is potentially useful in applications requiring high time resolution or in data-sparse regions of the oceans that might be covered by an ocean data buoy system.

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J. A. Schroeder, J. R. Jordan, and M. T. Decker

Abstract

A modular design for a ground-based thermodynamic profiler is presented, based on experience with a six-channel microwave radiometer that has provided temperature, pressure, and moisture measurements continuously, unattended, since 1981. Each module consists of one pair of microwave channels, whose frequencies are chosen to facilitate the joint use of radio-frequency (RF) components, thus reducing hardware costs by nearly half. The number of modules included in a given system can be chosen to suit the altitude and accuracy requirements for that particular application. The accuracy of temperatures and pressure heights retrieved from simulated profilers with 4 to 18 channels is presented to illustrate the tradeoff between cost and accuracy.

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D. C. Hogg, F. O. Guiraud, J. B. Snider, M. T. Decker, and E. R. Westwater

Abstract

An instrument that remotely senses the integrated amounts of water vapor and liquid on a path through the atmosphere is discussed. The vapor and liquid are measured simultaneously but independently by microwave radiometers. Comparison of the accuracy in measurement of vapor is made with radiosondes, and of liquid with an independent method employing transmission from a geosynchronous satellite. The instrument is designed for unattended operation; examples of measured data are given. Applications including observations for weather forecasting, weather modification, solar-radiation studies, and instrumentation for geodetic metrology are also discussed.

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E. R. Westwater, M. T. Decker, A. Zachs, and K. S. Gage

Abstract

This paper describes the results of a three-week experiment in which ground-based microwave radiometricmeasurements were combined with VHF radar measurements of tropopause height to yield vertical temperature profiles. Several algorithms to derive tropopause height are presented and their results are comparedwith radiosondes. The best of the algorithms yields radar versus radiosonde rms differences of 0.65 km.By the use of the combined radar-radiometric method, improvements were obtained in rms temperatureaccuracy of as much as 2.0 K rms over the pure radiometric technique.

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W. L. Smith, H. E. Rvercomb, H. B. Howell, H. M. Woolf, R. O. Knuteson, R G. Decker, M. J. Lynch, E. R. Westwater, R. G. Strauch, K. P. Moran, B. Stankov, M. J. Falls, J. Jordan, M. Jacobsen, W. F. Dabberdt, R. McBeth, G. Albright, C. Paneitz, G. Wright, P. T. May, and M. T. Decker

During the week 29 October–4 November 1988, a Ground-based Atmospheric Profiling Experiment (GAPEX) was conducted at Denver Stapleton International Airport. The objective of GAPEX was to acquire and analyze atomspheric-temperature and moisture-profile data from state-of-the-art remote sensors. The sensors included a six-spectral-channel, passive Microwave Profiler (MWP), a passive, infrared High-Resolution Interferometer Sounder (HIS) that provides more than 1500 spectral channels, and an active Radio Acoustic Sounding System (RASS). A Cross-Chain Loran Atmospheric Sounding System (CLASS) was used to provide research-quality in situ thermodynamic observations to verify the accuracy and resolution characteristics of each of the three remote sensors. The first results of the project are presented here to inform the meteorological community of the progress achieved during the GAPEX field phase. These results also serve to demonstrate the excellent prospects for an accurate, continuous thermodynamic profiling system to complement NOAA's forthcoming operational wind profiler.

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J. C. Kaimal, N. L. Abshire, R. B. Chadwick, M. T. Decker, W. H. Hooke, R. A. Kropfli, W. D. Neff, F. Pasqualucci, and P. H. Hildebrand

Abstract

Three in-situ and five remote sensing techniques for measuring the height of the daytime convective boundary layer were compared. There was, as a rule, good agreement between the different systems when the capping inversion was steep and well defined, and some variability when the stratification was not so sharply defined. Two indirect methods for estimating boundary-layer heights from the length scales of convective motions in the layer are also discussed.

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D. C. Hogg, M. T. Decker, F. O. Guiraud, K. B. Earnshaw, D. A. Merritt, K. P. Moran, W. B. Sweezy, R. G. Strauch, E. R. Westwater, and C. G. Little

Abstract

A remote-sensing system for continuously profiling the troposphere is discussed; the prototype Profiler utilizes radio wavelengths, thereby achieving essentially all-weather operation. Designed for unattended operation, the Profiler employs radiometric and Doppler radar technology. Design, construction and calibration of the instruments composing the Profiler system are described along with some of the physics and mathematics upon which their operation is based. Examples of profiles and other variables of meteorological interest are given, and comparisons are made with simultaneous data from colocated operational (NWS) sondes. An algorithm based on climatological statistics of measurements by radiosonde is used in the radiometric retrieval process, but there is no reliance of the products of the Profiler upon any current radiosonde data. The role of the Profiler in mesoscale and synoptic weather forecasting and its relationship to systems employing sounders on satellite platforms are also discussed.

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