An Operational Method for the Determination of Vertical Velocities

Abstract

An ?-chart is obtained from a combination of charts of the thickness advection and the vorticity advection. The advection charts can be rapidly computed by measurement of the areas of the quadrilaterals formed by the cross-patterns of 1000-mb contours and 1000?500 mb thicknesses, and space mean (Z) contours and Z?Z isolines. These charts are themselves of considerable use in short-range forecasting techniques. A simple graphical combination of these charts results in an ?-chart. The ?-values, so derived, have been successfully used in quantitative precipitation computations.