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Donald C. Thompson

Abstract

The recovery factors of miniature bead thermistors as used in meteorological rocketsondes were measured at subsonic Mach numbers using a whirling arm device inside a vacuum chamber. Measured values were near 0.75 at sea level pressure and remained relatively constant with pressure up to a pressure altitude of about 30 km. Above a pressure altitude of 40 km the recovery factors steadily increased with altitude and at 65 km values between 1.10 and 1.45 were recorded.

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Donald C. Thompson
and
D. P. Keily

Abstract

Preliminary results are presented of laboratory studies of the heat balance in rocketsonde semiconductor thermometers. The so-called dissipation constant of rocketsonde thermistors is a marked function of altitude above about 45 km. At high altitudes also, the temperature rise in the thermistor due to solar radiation is strongly dependent upon the radiation absorbed by the lead wires as well as by the beam proper. Speed of response is found to be dependent upon the convective heat transfer of the leads as well as of the thermistor bead.

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Owen E. Thompson
,
Mitchell D. Goldberg
, and
Donald A. Dazlich

Abstract

Two Pattern recognition procedures are developed to provide improvements to first-guess fields for satellite temperature retrievals. The first is a technique whereby a radiometer measurement may be used to select one or more historical radiosonde temperature profiles as analog estimates of ambient thermal structure. The vertical scales of the analogs are those of radiosondes—the vertical resolving power of the satellite radiometer being relevant only to a decision process. The analog selection process is shown to be much more effective if implemented in an orthogonalized space of measurement information. The second procedure is one which partitions a priori dependent data into shape-coherent pattern libraries using structure information inherent in the data itself. This is an alternative to traditional partitioning schemes whereby proxy classifiers such as season, location and surface type are used.

These pattern recognition techniques are shown to be capable of reducing first-guess profile errors by nearly 50%, in an independent test of about 800 diverse retrievals. The impact of pattern recognition on temperature retrieval error is assessed using regression and physical-iterative retrieval algorithms. The influence of improved first-guess fields is markedly different on these two types of algorithms. Pattern recognition is shown to have a strong, positive impact on the physical-iterative method but little significant impact on regression when evaluated in an overall batch sense. A case study suggests that a small number of very poor retrievals may particularly mask the potential benefits of pattern recognition on both methods.

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Owen E. Thompson
,
Donald D. Dazlich
, and
Yu-Tai Hou

Abstract

The inverse problem of satellite temperature profile retrieval is well known to be ill-posed. Ibis means that not only is a vertical temperature profile solution not unique, but that two solutions can be very different from each other. A set of atmosphere-like, and true atmospheric examples of significantly dissimilar inverse solutions, were sought and found, using an 11-channel simulated HIRS sounding radiometer. Using the Riemann-Lebesgue Lemma for guidance, it is shown that simultaneous, numerical solutions of an atmospheric character may differ by as much as 10 K between 10–1000 mb. However, an empirical search for dissimilar solutions in the natural atmosphere reveals an extremely low probability of finding two significantly different RAOBs which produce radiance measurements whose differences cannot be resolved by the satellite radiometer. The empirical results are used to derive a first estimate of the limits of retrievability, analogous to the limits of predictability derivable from the ill-posed nature of the numerical weather prediction problem.

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Nathaniel S. Winstead
,
Todd D. Sikora
,
Donald R. Thompson
, and
Pierre D. Mourad

Abstract

Synthetic aperture radar (SAR) images of oceans and the Great Lakes have provided a highly detailed means of observing atmospheric boundary layer phenomena such as convection, land breezes, and internal gravity waves. This is possible because the backscattered radiation detected by SAR can be dominated by scattering from wind-driven capillary waves whose spatial variation is visible as patterns in the SAR images. In this paper, we present two case studies in which SAR images taken over Lake Superior demonstrate spatial variability in the surface wind stress created over the lake by coincident gravity waves and boundary layer convection during cold air outbreaks. Of particular interest is the direct influence of the gravity waves on the lake-surface stress despite the intervening highly convective atmosphere as well as the detailed view of the fetch dependence of that stress.

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Nathaniel S. Winstead
,
Brian Colle
,
Nicholas Bond
,
George Young
,
Joseph Olson
,
Kenneth Loescher
,
Frank Monaldo
,
Donald Thompson
, and
William Pichel

The steeply rising coastal terrain of southeast Alaska can produce a wide variety of terrain-induced flows such as barrier jets, gap flows, and downslope wind storms. This study uses a combination of satellite remote sensing, field observations, and modeling to improve our understanding of the dynamics of these flows. After examining several thousand synthetic aperture radar (SAR) high-resolution wind speed images over the Gulf of Alaska, several subclasses of barrier jets were identified that do not fit the current conceptual model of barrier jet development. This conceptual model consists of an acceleration and turning of the ambient cross-barrier flow into the along-barrier direction when the ambient low-level flow is blocked by terrain; however, the SAR imagery showed many barrier jet cases with significant flow variability in the along-coast direction as well as evidence for the influence of cold, dry continental air exiting the gaps in coastal terrain. A subclass of jets has been observed where the transition from the coastal to the offshore flow is abrupt.

The results from these climatological studies have motivated modeling studies of selected events as well as field observations from the Southeast Alaska Regional Jets (SARJET) experiment field campaign in the Gulf of Alaska during fall of 2004. This paper will highlight preliminary results obtained during SARJET, which collected in situ measurements of barrier jets and gap flows using the University of Wyoming's King Air research aircraft.

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