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:
“In the cowslips peeps I lie,
Hidden from the buzzing fly,
While green grass beneath me lies,
Pearled wi’ dew like fishes’ eyes,
Here I lye, a clock-a-clay,
Waiting for the time o’ day.”
—John Clare (1793–1864)
“We should have learnt by now that laws and court decisions can only point the way. They can establish criteria of right and wrong. And they can provide a basis for rooting out the evils of bigotry and racism. But they cannot wipe away centuries of oppression and injustice—however much we might desire it.”
—Hubert H. Humphrey (1911–1978)
“Could it be that those who were reared in the postwar years really were spoiled, as we used to hear? Did a child-centered generation, raised in depression and war, produce a self-centered generation that resents children and parenthood?”
—C. John Sommerville (20th century)