Dan Robinson
I did some searching on this simple question but haven't been able to find anything concrete.
I've always assumed that the temperature of air cannot fall below its dewpoint, due to latent heat warming when saturation occurs. In other words, the dewpoint is always less than or equal to the temperature. So, the temperature can only continue falling if the dewpoint falls (due to mixing). Is this true?
Applying this in a practical sense - assuming a low T/Td spread, little to no advection or mixing and good radiational cooling (clear skies), can a forecast low overnight temperature be estimated using the observed dewpoints?
For example, if the surface T/Td is 40/31F at 8PM in October with light winds and clear skies, you can normally count on frost. So, if observations show 40/34F with light winds and clear skies, can you safely say that frost is unlikely - IE, can you assume the temp will 'bottom out' at 34F and go no lower, even if 34F is reached at midnight?
I've always assumed that the temperature of air cannot fall below its dewpoint, due to latent heat warming when saturation occurs. In other words, the dewpoint is always less than or equal to the temperature. So, the temperature can only continue falling if the dewpoint falls (due to mixing). Is this true?
Applying this in a practical sense - assuming a low T/Td spread, little to no advection or mixing and good radiational cooling (clear skies), can a forecast low overnight temperature be estimated using the observed dewpoints?
For example, if the surface T/Td is 40/31F at 8PM in October with light winds and clear skies, you can normally count on frost. So, if observations show 40/34F with light winds and clear skies, can you safely say that frost is unlikely - IE, can you assume the temp will 'bottom out' at 34F and go no lower, even if 34F is reached at midnight?