The time scale here is an advective time scale which is appropriate for pressure systems which move at approximately the speed of the horizontal wind,
{"Image DocumentName": "The time scale here is an advective time scale which is appropriate for pressure systems which move at approximately the speed of the horizontal wind, as is observed for synoptic scale motions.", "Image ImageDescription": "Thus, L/U is the time required to travel a distance L at a speed U. It should be pointed out here that the synoptic scale vertical velocity is not a directly measurable quantity. However, we show later that the magnitude of W can be deduced from knowledge of the horizontal velocity field. We can estimate the magnitude of each term in eqns and 2.25 for synoptic scale motions at a given latitude. It is convenient to consider disturbances centered at latitude \u03a6o = 45\u00b0N, and introduce the notation: fo = 2\u03a9sin\u03a6o = 2\u03a9cos\u03a6o \u2248 10-4s-1. The radius of the earth, a = 6.37x106m = 0.637x107m \u2248 1x107m.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}