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John E. Gaynor

Abstract

We explain, using in situ data, some of the mechanisms contributing to acoustic backscatter measured using an active, vertically pointing echosonde (acoustic sounder) mounted aboard ship in the tropical Atlantic. Averaged tethered-sonde profiles indicate that the substantial wind shear through the low-level stable layer in the wake of precipitating convection contributes to the acoustic backscatter from this layer. The undisturbed top of the mixed layer shows much weaker shear and no echo, although the average stabilities are nearly the same in the undisturbed and wake cases. Combining theory with data provides an explanation of the importance of moisture in acoustic backscatter. In the suppressed mixed layer (little or no precipitating convection) the contribution to the backscatter due to moisture (Ce 2) approaches a factor of 3 greater than temperature fluctuations alone (CT 2. In the disturbed boundary layer (organized convection) and moderately disturbed boundary layer (isolated convection), the moisture contributes less than 20%. Except near the top and near the bottom of the suppressed mixed layer, the co-fluctuations of moisture and temperature (Cet contribute immaterially. The categorized profiles of CT 2, Ce 2 and Cet do not exhibit clear tendencies toward Z −4/3 slopes predicted by other authors.

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John E. Gaynor and Christopher A. Biltoft

Abstract

In an experiment conducted at the Boulder Atmospheric Observatory (BAO), comparisons were made between two types of sonic anemometer and thermometer systems. One sonic anemometer was a single-axis system manufactured by Campbell Scientific, Inc., (SCI) and the other the type routinely used on the BAO tower. It is similar to the sensors manufactured by Applied Technologies, Inc., and AIR Inc. Two identical Campbell Scientific systems were mounted on each side or the BAO System and comparisons made over a range of atmospheric surface layer conditions. The means and standard deviation of the vertical wind component and temperature, along with the temperature flux from each system, showed good agreement. important differences in temperature fluctuation data due to the thermocouple filtering are noted. The effect of these differences on the measured heat fluxes and temperature variances is significant and discussed in some detail. It appears that the response of the CSI thermal mass to solar radiation was the major reason for the discrepancies.

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Earl E. Gossard, Russell B. Chadwick, Thomas R. Detman, and John Gaynor

Abstract

Radars and acoustic sounding systems sense properties of the turbulence structure of the atmosphere. If atmospheric turbulence can be related to the mean gradient parameters, Doppler radars and acoustic sounders can provide information about height profiles of quantities such as temperature and refractive index as well as wind in stable regions of the atmosphere. In this paper turbulent and mean quantities were measured on the 300 m meteorological tower at the Boulder Atmospheric Observatory near Erie, Colorado, and the relationships between the turbulent and mean gradient quantities were examined in order to evaluate hypotheses for simplifying the kinetic energy balance and refractive index variance equations. FM-CW radar measurements of backscattered power and Doppler spectral width were also made for comparison with tower-measured refractive index spectra and Doppler velocity spectra. Height distributions of the turbulent dissipation rate within stable layers are shown and viscous cutoff radar wavelengths calculated.

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Paul A. Hirschberg, Elliot Abrams, Andrea Bleistein, William Bua, Luca Delle Monache, Thomas W. Dulong, John E. Gaynor, Bob Glahn, Thomas M. Hamill, James A. Hansen, Douglas C. Hilderbrand, Ross N. Hoffman, Betty Hearn Morrow, Brenda Philips, John Sokich, and Neil Stuart

The American Meteorological Society (AMS) Weather and Climate Enterprise Strategic Implementation Plan for Generating and Communicating Forecast Uncertainty (the Plan) is summarized. The Plan (available on the AMS website at www.ametsoc.org/boardpges/cwce/docs/BEC/ACUF/2011-02-20-ACUF-Final-Report.pdf) is based on and intended to provide a foundation for implementing recent recommendations regarding forecast uncertainty by the National Research Council (NRC), AMS, and World Meteorological Organization. It defines a vision, strategic goals, roles and respon- sibilities, and an implementation road map to guide the weather and climate enterprise (the Enterprise) toward routinely providing the nation with comprehensive, skillful, reliable, and useful information about the uncertainty of weather, water, and climate (hydrometeorological) forecasts. Examples are provided describing how hydrometeorological forecast uncertainty information can improve decisions and outcomes in various socioeconomic areas. The implementation road map defines objectives and tasks that the four sectors comprising the Enterprise (i.e., government, industry, academia, and nongovernmental organizations) should work on in partnership to meet four key, interrelated strategic goals: 1) understand social and physical science aspects of forecast uncertainty; 2) communicate forecast uncertainty information effectively and collaborate with users to assist them in their decision making; 3) generate forecast uncertainty data, products, services, and information; and 4) enable research, development, and operations with necessary information technology and other infrastructure. The Plan endorses the NRC recommendation that the National Oceanic and Atmospheric Administration and, in particular, the National Weather Service, should take the lead in motivating and organizing Enterprise resources and expertise in order to reach the Plan's vision and goals and shift the nation successfully toward a greater understanding and use of forecast uncertainty in decision making.

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