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C. D. Rodgers

Abstract

A westward propagating temperature wave of wavenumber 1 observed in the Nimbus 5 Selective Chopper Radiometer measurements has been tentatively identified as the 5-day global Rossby mode discussed by Grisler and Dickinson (1976). Its amplitude is typically 0.5 K, and its period varies within the range 4.5 to 6.2 days.

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C. D. Rodgers

Abstract

The Backus-Gilbert method for the inverse problem of remote sounding is extended to include the case when a priori statistics of the solution are available. The results show that a considerable improvement in resolution and/or noise can be obtained both for idealized and realistic situations.

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D. M. Rodgers, K. W. Howard, and E. C. Johnston

Abstract

An important class of convective weather system, the mesoscale convective complex (MCC), presents many challenges and problems to both the research and operational communities. In addition, thew very large and long-lived thunderstorm systems have a significant social and economic impact resulting from associated severe weather phenomena and widespread beneficial rain. Enhanced infrared satellite images were surveyed to document MCCs which occurred over the United States during 1982. Thirty-seven convective mesosystems were identified that displayed satellite-observable characteristics which satisfied the MCC criteria described by Maddox. Details of the life cycles of the 37 cases are given and several specific cases are discussed. Current and proposed future research will focus on what are perceived to be key questions surrounding these important weather systems. This annual summary is offered as a starting point for scientists interested in pursuing studies of mesoscale convective weather systems.

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F. W. Taylor, A. Lambert, R. G. Grainger, C. D. Rodgers, and J. J. Remedios

Abstract

Observations of polar stratospheric clouds by the Improved Stratospheric and Mesospheric Sounder (ISAMS) experiment on the Upper Atmospheric Research Satellite (UARS) have revealed new details of their global properties and behavior. These include the vertical and horizontal spatial distributions of Arctic and Antarctic polar stratospheric clouds (PSCs) as a function of time and air temperature, their optical thicknesses and estimated densities, their spectral properties, and their inferred composition. In particular, ISAMS spectral data allows different PSC types to be distinguished from each other and from volcanic aerosol by their compositional differences. Northern PSCs during the 1991/92 season are found to be more ephemeral and more compact than reported in previous years and to differ markedly in scale from those in the Southern Hemisphere, which cause the Antarctic ozone hole by activating stratospheric chlorine chemistry. There were only two episodes of dense PSC formation in the 1991/92 northern winter, one of which took place in sunlight. The latter correlates well with UARS/Microwave Limb Sounder observations of enhanced chlorine monoxide, but substantial amounts of chlorine monoxide were also reported at times and places with at most very minor PSC activity.

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Matthew H. Hitchman, John C. Gille, Clive D. Rodgers, and Guy Brasseur

Abstract

An examination of satellite-derived temperatures reveals that the winter polar stratopause is usually elevated and warmer than the adjacent midlatitude stratopause. This “separated stratopause” occurs in both hemispheres, but is more pronounced and persistent in the southern winter. It descends with time towards spring and exhibits week to week variability. Observational diagnostics and results from a two dimensional (2-D) model suggest that gravity wave driving can account for this separated polar stratopause by driving a meridional circulation with downwelling over the winter pole. In the model, the solar heating pattern induces stronger winter westerlies than summer easterlies, which leads to a stronger gravity wave driven circulation in the winter hemisphere. Spherical geometry and the high latitude location of the winter westerly jet combine to yield a concentrated region of downwelling. Model results suggest that descent of the temperature maximum with time is probably caused by wave–mean flow interaction.

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