The dew point depression (T-Td) is the difference between the temperature and dew point temperature at a certain height in the atmosphere.
The smaller the difference, the more moisture there is, and the higher the relative humidity. In the lower troposphere, more moisture (small dew point depression) results in lower cloud bases and is also important to severe thunderstorms. Conversely, instability is increased when there is a mid-level dry layer (large dew point depression) known as a "dry punch", which is favorable for convection if the lower layer is buoyant.
As it measures moisture content in the atmosphere, the dew point depression is also an important indicator in agricultural and forest meteorology, particularly in predicting wildfires.
Famous quotes containing the words dew, point and/or depression:
“The very dew seemed to hang upon the trees later into the day than usual, as on the sides of mountains.”
—Henry David Thoreau (1817–1862)
“The point of vision and desire are the same.”
—Wallace Stevens (1879–1955)
“During depression the world disappears. Language itself. One has nothing to say. Nothing. No small talk, no anecdotes. Nothing can be risked on the board of talk. Because the inner voice is so urgent in its own discourse: How shall I live? How shall I manage the future? Why should I go on?”
—Kate Millett (b. 1934)