Why do meteorological charts show contour heights etc., and not isobars?
In meteorology, we don’t take a fixed height, and measure the pressure of that height (though in the early days of upper air meteorology, that was in fact done), but instead define a pressure level ( 850 hPa, 700 hPa, 500 hPa etc.), and find the height (amsl) at which that pressure value is found. There are several reasons why this is so: It was easier when balloon sounding using pressure sensors was the only method of upper air measurement to note the height at which pressure levels were found; and in computation of upper dynamics (e.g. wind vectors), by using this scheme you can eliminate density from the equations … an obvious variable. There are also advantages when relating the upper air patterns to the readings on a pressure-altimeter.). On a constant pressure level map then (say 500 hPa), you will have heights plotted as, for example 5340, 5432, 5286, 5567 metres etc., and then contours are drawn (just like isobars, which in fact they are), and so we get to the often smoothly
