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Mugwumping It

The approach to the use of English and metric units in the articles appearing here usually is that of the political mugwumps of a century ago. As older persons will recall, a mugwump was one who stood on the political fence with his "mug" on one side and his "wump" on the other, and was afraid to come down on either side.

My main excuse for the balancing act is that this column appears in newspapers in both Alaska and Canada, so it is desirable to mix the units, or use both, to accommodate readers on both sides of the boundary. This practice of course creates some awkwardness.

Unfortunately it contributes to errors, too. Editors who try to eliminate one or the other sets of units make errors, and I do, too. My most recent goof appeared several weeks ago in an article on why local differences in air temperature occur. In that article I correctly stated that the adiabatic lapse rate was 0.6°C per 100 meters. But my conversion to degrees Fahrenheit per 100 feet was wrong. It is near 0.3°F per 100 feet instead of the stated 3°F per 100 feet.

Having made that error, I carried it on in the calculation of the expected difference between hillside and valley floor temperatures and arrived at postulated differences that were roughly ten times greater than proper. Thus, the cited reports of hillside air temperatures sometimes being 10°F to 20°F lower than on the valley floor below are not explained by the air column having, in those cases, a temperature profile near the adiabatic lapse rate. (Air within a column having that temperature distribution tends to move neither up or down.) To explain the observed differences, horizontal movement of cold air from another locality probably is required.

The cited error did not affect the discussion given of temperature differences when inversions pertain. Then, the air near the valley floor is colder than the air on the hillside.