Page 48 - ภาษาอังกฤษสำหรับสายวิทยาการอุตุนิยมวิทยา

43

6. Isobars

The pressure at each statton is marked on the weather map and lines called Isobars are drawn
to connect the points of equal pressure. Many of these lines make complete circles and
surround areas marked H (high) or L (1ow). Isobars are similar to the lines that are drawn on
regular surface maps to show elevation. However, instead of indicating the elevation of terrain
and the steepness of slopes, Isobars indicate the amount of pressure and steepness of pressure
gradients. If the gradient (slope) is steep, the isobars will be close together, s and the wind will
be strong. If the is gradual, the lsobars will be far apart, and the win light. Isobars provide useful
information about the winds aloft. Close ith, wind direction is modified by the terrain over ses,
and wind speed is reduced by friction with The At tudes two or three thousand feet above the
surface, however Is greater and the direction is usually parallel to the isobars.

Figure 4