Comments on “Observations of a Mesoscale Ducted Gravity Wave”

G. L. Browning CIRA, Colorado State University, Fort Collins, Colorado

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H-O. Kreiss Department of Mathematics, University of California, Los Angeles, Los Angeles, California

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D. W. van de Kamp Forecast Systems Laboratory, NOAA/ERL, Boulder, Colorado

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Abstract

Recently, a mathematical theory has been developed that proves that there are two main components of the solution of the forced dynamical system that describes a mesoscale storm driven by cooling and heating processes. The component that contains most of the energy of the solution (and is therefore called the dominant component) satisfies a simple nonlinear system devoid of gravity and sound waves. The residual component of the solution satisfies a forced gravity wave equation and essentially does not interact with the dominant component. The mathematical theory also provides information about the amplitude, wavelength, and period of the gravity waves. In the paper entitled “Comments on ‘Use of ducting theory in an observed case of gravity waves,”’ Dr. F. M. Ralph has claimed that the new gravity wave theory is not consistent with profiler observations of vertical velocity in his earlier paper entitled “Observations of a mesoscale ducted gravity wave.” Here it is shown that the new theory is completely consistent with profilers that have documented error bounds on the vertical velocity measurements. In the case that the new theory is claimed to be inconsistent with observational data, the data were obtained from a profiler with undocumented accuracy of the vertical velocity measurements in the precipitating case, and the two components of the solution were not properly separated.

Corresponding author address: Dr. Gerald L. Browning, Forecast Systems Laboratory, NOAA/ERL R/E/FS, 325 Broadway, Boulder, CO 80303.

Abstract

Recently, a mathematical theory has been developed that proves that there are two main components of the solution of the forced dynamical system that describes a mesoscale storm driven by cooling and heating processes. The component that contains most of the energy of the solution (and is therefore called the dominant component) satisfies a simple nonlinear system devoid of gravity and sound waves. The residual component of the solution satisfies a forced gravity wave equation and essentially does not interact with the dominant component. The mathematical theory also provides information about the amplitude, wavelength, and period of the gravity waves. In the paper entitled “Comments on ‘Use of ducting theory in an observed case of gravity waves,”’ Dr. F. M. Ralph has claimed that the new gravity wave theory is not consistent with profiler observations of vertical velocity in his earlier paper entitled “Observations of a mesoscale ducted gravity wave.” Here it is shown that the new theory is completely consistent with profilers that have documented error bounds on the vertical velocity measurements. In the case that the new theory is claimed to be inconsistent with observational data, the data were obtained from a profiler with undocumented accuracy of the vertical velocity measurements in the precipitating case, and the two components of the solution were not properly separated.

Corresponding author address: Dr. Gerald L. Browning, Forecast Systems Laboratory, NOAA/ERL R/E/FS, 325 Broadway, Boulder, CO 80303.

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