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William L. Grose and Kenneth V. Haggard

Abstract

The present study describes the analysis of a sudden warming which developed spontaneously during one winter of a 33-month simulation using a three-dimensional, spectral, quasi-geostrophic model. The changes that occurred in the circulation and thermal structure of the winter polar stratosphere during the warming are shown to be in close agreement with observed behavior. That is, characteristic features of stratospheric warmings such as 1) enhanced vertical flux of eddy energy into the stratosphere, 2) rapid temperature increase in high latitudes with a reversal of the zonal mean temperature gradient between midlatitude and pole, 3) destruction of the circumpolar cyclonic vortex, and 4) marked deceleration of the westerly jet and the appearance of zonal mean easterlies are reproduced by the model. The energetics of the warming are also consistent with features characteristic of observed events. In addition, certain aspects of the dynamical development of the present model simulation are shown to be in agreement with results from other models, but certain contrasting aspects will be discussed.

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Ellis E. Remsberg, Kenneth V. Haggard, and James M. Russell III

Abstract

The most widely used version of the Nimbus-7 LIMS middle atmosphere dataset is the set of high quality, daily, and zonal Fourier coefficients that resolve information out to six wavenumbers at 12 UTC. A Kalman filter algorithm was applied to the original profile data in order to generate those fields for the data archive or LAMAT product. The characteristics and implementation of the algorithm are described in some detail, along with examples of the output for each of the LIMS parameters. Criteria for judging the quality of the derived results are discussed and include: (i) standard deviation of the fit between individual profiles and the mapped field at the same longitudes, (ii) comparisons between the separate analyses of the ascending and descending orbital mode coefficients, (iii) continuity of the fields with latitude and pressure and (iv) comparisons of sequences of daily maps of the different parameters. The degree to which the filter fits the original data is determined by the estimated precision of the satellite measurements.

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