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:
“We should be blessed if we lived in the present always, and took advantage of every accident that befell us, like the grass which confesses the influence of the slightest dew that falls on it; and did not spend our time in atoning for the neglect of past opportunities, which we call doing our duty.”
—Henry David Thoreau (1817–1862)
“I would rather produce my passions than brood over them at my expense; they grow languid when they have vent and expression. It is better that their point should operate outwardly than be turned against us.”
—Michel de Montaigne (1533–1592)
“In the larger view the major forces of the depression now lie outside of the United States, and our recuperation has been retarded by the unwarranted degree of fear and apprehension created by these outside forces.”
—Herbert Hoover (1874–1964)