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A. Henderson-Sellers, A. J. Pitman, B. Henderson-Sellers, D. Pollard, and J. M. Verner

Abstract

In addition to model validation techniques and intermodel comparison projects, the authors propose the use of software engineering metrics as an additional tool for the enhancement of “quality” in climate models. By discriminating between internal, directly measurable characteristics of structural complexity, and external characteristics, such as maintainability and comprehensibility, a way to benefit climate modeling by the use of easily derivable metrics is explored. As a small illustration, the results of a pilot project are presented. This is a subproject of the Project for Intercomparison of Landsurface Parameterization Schemes in which the authors use some typical structural complexity metrics, namely, for control flow, size, and coupling. Finally, and purely indicatively, the authors compare the results obtained from these metrics with scientists’ subjective views of the psychological complexity of the programs.

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James B. Mead, Geoffrey Hopcraft, Stephen J. Frasier, Brian D. Pollard, Christopher D. Cherry, Daniel H. Schaubert, and Robert E. McIntosh

Abstract

This paper describes the turbulent eddy profiler (TEP), a volume-imaging, UHF radar wind profiler designed for clear-air measurements in the atmospheric boundary layer on scales comparable to grid cell sizes of large eddy simulation models. TEP employs a large array of antennas—each feeding an independent receiver—to simultaneously generate multiple beams within a 28° conical volume illuminated by the transmitter. Range gating provides 30-m spatial resolution in the vertical dimension. Each volume image is updated every 2–10 s, and long datasets can be gathered to study the evolution of turbulent structure over several hours. A summary of the principles of operation and the design of TEP is provided, including examples of clear-air reflectivity and velocity images.

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Brian D. Pollard, Samir Khanna, Stephen J. Frasier, John C. Wyngaard, Dennis W. Thomson, and Robert E. McIntosh

Abstract

The local structure and evolution of the convective boundary layer (CBL) are studied through measurements obtained with a volume-imaging radar, the turbulent eddy profiler (TEP). TEP has the unique ability to image the temporal and spatial evolution of both the velocity field and the local refractive index structure-function parameter, 2n. Volumetric images consisting of several thousand pixels are typically formed in as little as 1 s. Spatial resolutions are approximately 30 m by 30 m by 30 m.

CBL data obtained during an August 1996 deployment at Rocks Springs, Pennsylvania, are presented. Measurements of the vertical 2n profile are shown, exhibiting the well-known bright band near the capping inversion at z i, as well as intermittent plumes of high 2n. Horizontal profiles show coherent 100-m-scale 2n and vertical velocity (w) structures that correspond to converging horizontal velocity vectors. To quantify the scales of structures, the vertical and streamwise horizontal correlation distances are calculated within the TEP field of view.

To study the statistics and scales of larger structures, effective volumes larger than the TEP field of view are constructed through Taylor’s hypothesis. Statistics of 2n and w time series are compared to an appropriately scaled large eddy simulation (LES). While w time series comparisons agree very well, the LES 2n predictions agree only with some of the measured data. Finally, the scales of 2n structures in the TEP time series measurements are calculated and compared to the scales in the LES spatial domain. Good agreement is found only near the capping inversion layer, the area of largest structures. This study highlights the unique capabilities of the TEP instrument, and shows what are believed to be the first statistical comparisons of measured 2n data with LES derived results.

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