A diagnosis of adiabatic production and destruction of kinetic energy by the meridional and zonal motions of the atmosphere

Abstract

Dr. J. S. A. GREEN: I do not believe that the energy production due to each component of the motion can be separated in the way suggested, but only (at best) in terms of u(a+/ax -fu) and v( a+/ay + fu) each of which is a small residual compared to the values shown.The separated data as it stands, is of interest in that it shows correlations between u and a+/ax over the American continent (positive and negative south and north of latitude 3 5 ' ) but these indicate almost wholly the persistent orientation of the geostrophic component of the flow and are therefore nearly independent of processes of energy production. The cancellatory nature of the contribution from the two terms again supports this view.It would be useful if the quantities displayed in the figures and the units involved were clarified.Dr. R. S. HARWOOD: Professor Kung's study covers a fairly narrow band of longitudes; can he give us more information about how representative his fields of -u a+lax, -v aelay are of the global scale motions?Professor R. C. SUTCLIFFE: To a first approximation (geostrophic), ua+/ax = -va+/ay (each proportional to uv) it is inevitable that they should nearly balance giving a small residual for ua+/ax + va+jay. Thus the separate values of these terms are mainly an expression of the geometry of the flow patterns and do not seem to have any significance in the kinetic energy problem.Professor P. A. SHEPPARD: In order to obtain some appreciation of the physical content and implications of the author's results one needs to examine carefully the nature of the computations carried out and presented by the author. As I understand it the author has computed daily mean values of -V.V+ (or of -ua+lax and -va+/ay) averaged over 5" latitude zones stretching across the North American continent and has then presented monthly and seasonal averages of these daily mean values. Thus it would appear that the results embrace the contribution to the production (positive or negative) of kinetic energy by some rather ill-defined combination of monthly (or seasonal) mean motion and synoptic-scale motions whose spatial features are averaged in longitude but whose temporal features (beyond a day) are retained. In regard to the former, because of the standing long-wave pattern of the mean motion the contribution by that mean motion bears no necessary relation to the production of kinetic energy by meridional mean motion as commonly understood i.e. by meridional motion averaged round latitude circles. When, moreover, the uncertain contribution of some features of the synoptic-scale motions is born in mind it is surprising to find the author interpeting his results very largely in terms of the effects of Hadley and Ferrel meridional circulations. He may be correct in his interpretation but some breakdown of his values of -V.V+ is surely indicated if they are to throw light on how the generation of kinetic energy is brought about.Professor E. C. KUNG: (in reply): To Dr. Green, I should like to say that it is true that the net contribution of the energ...

Energy Transformations in the Tropical Circulation During the FGGE Winter

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