Abstract
Two separate equations for the barometric tendency at a fixed point, or the height tendency of a rpessure surface are derived a from the hydrostatic equation, and (b) from the equations of motion.
The hydrostatic tendency equation, which represents a modification of the MargulesβBjerknes equations, relates the barometric tendency (or the height tendency) to the winds integrated through isobaric layers, and also to the patterns of contours and βthicknessesβ of the layers. The separate contributions to the pressure variations rendered by the thermal wind, the cyclostrophic components and the horizontal divergence are identified and discussed. Methods of identifying the layer, or layers, that constitute the site of the processes and of assessing the magnitude of their contributions to the pressure variations are outlined. The reaction of the pressure distribution at sea level to the circulation aloft is discussed in some detail, particularly wit regard to the travel and development of cyclones, anticyclones, etc.
The dynamical tendency equation relates the barometric tendency to the accelerations integrate through isobaric layers. A brief discussion of this equation in relation to typical circulations is given.