"The specification of a physical process by the phrase due_to_process means that the quantity named is a single term in a sum of terms which together compose the general quantity named by omitting the phrase. \"tendency_of_X\" means derivative of X with respect to time. \"Eastward\" indicates a vector component which is positive when directed eastward (negative westward). Wind is defined as a two-dimensional (horizontal) air velocity vector, with no vertical component. (Vertical motion in the atmosphere has the standard name upward_air_velocity.)" . . "Climate and Forecast (CF)" . . "tendency of eastward wind due to advection" . . .