Mean Sea Level Pressure Highs and Lows Ridges and Troughs Fronts Thickness Temperature Advection Definitions

Ridges and Troughs Recall that lines of constant pressure called isobars are drawn on weather maps so that areas of high and low pressure can be identified. Notice on the map there are areas where isobars bulge northward or dip southward. These are areas that we call ridges and troughs. Meteorologists often draw a dashed line through the center of the elongated area of low pressure to identify the trough. Fronts lie in troughs. The reason why troughs and ridges are so significant is because they dramatically influence our weather. We often associate low pressure with wet or cloudy weather and high pressure with fair weather. Since troughs are elongated areas of low pressure it is reasonable to expect falling pressure, rising motion, positive vorticity advection and low-level convergence in advance of a trough. Questions