Temperature Inversions

In Chapter 2, we learn that the temperature in the troposphere generally decreases with height at a rate of about 6.5 degrees C/km. These are average conditions, and in fact the temperature profile of the atmosphere varies considerably. In the case of cool, polar airmasses like the one currently over Vermont, there are small layers of the troposphere where the temperature actually increases with height. These are called temperature inversions.
The temperature profile chart at
right (the red line measures temperature) is taken this morning at 12Z (8AM) over Maniwaki, Quebec, and represents the sounding station closest to Vermont from the the North. You will note here that the temperature between 925 and 850 mb (about 2500 to 4500 ft) actually rises from about 6 to 10 degrees C (about 43 to 50 degrees F). On days like this, you'll find that the temperature is actually warmer at the top of a mountain than at its foot!

Charts like this that plot temperature against heigh are called STUVE diagrams. You can accesscurrent charts like this one at the LSC-MET webpage for upper-air data.