Last week, for several days I had been noticing that Fort Payne had been having hotter daytime temperatures than I would expect. For example, Fort Payne might have a temperature of 98 degrees and Tuscaloosa might only be at 94. That seemed a bit odd to me since Tuscaloosa is a good bit further south than Gadsden. Additionally I noticed that Fort Payne was several degrees warmer than a weather station on Sand Mountain several miles to the west. That made sense since the weather station at the airfield in Fort Payne is in the Big Wills valley and the other station was several hundred feet higher in elevation on top of Sand Mountain.
After wondering for a while why Fort Payne would be hotter than Tuscaloosa several days consecutively, I consulted Jason Simpson. It didn't take long for us to come up with a theory. It could be possible that the reason why Fort Payne was several degrees hotter than Tuscaloosa is because Fort Payne was under the influence of adiabatic heating because of its location in a valley, and Tuscaloosa was not. Now, this is just a theory, and other factors could have been involved, but this particular factor definitely could have contributed to the situation.
So how exactly could adiabatic heating effect this situation? Well, to begin with, adiabatic processes occur without a heat transfer between a system (such as a parcel of air) and its surrounding environment. The parcel of air can warm and cool adiabatically by changing the atmospheric pressure on the parcel. This is done by changing the altitude of the parcel. When a parcel of air rises, the pressure decreases, and the air expands and cools. When a parcel descends, the pressure increases, the air is compressed, and the parcel heats up. Both of these processes are common near mountain slopes.
So, it could be possible that the weather station at Isbell Field in Fort Payne recorded a higher temperature than the station in Tuscaloosa, because air moving down from Sand Mountain into the valley was compressed enough to raise the temperature by a few degrees. Unsaturated air has a lapse rate of about 5.5 degrees per 1000 feet, which means that a parcel that descends 1000 feet will have a 5.5 degree rise in temperature. So, it is probable that Fort Payne, at several hundred feet lower elevation than the station on Sand Mountain, definitely experienced higher temperatures because of adiabatically heated air. Tuscaloosa, on the other hand, has no change in elevation of that magnitude anywhere close, so adiabatic heating induced by topography would not be a factor.
So, that may be the reason why Fort Payne was a little bit hotter than Tuscaloosa for several days last week.
Drew McCombs
ABC 33/40 Weather Intern
abc3340wx2@gmail.com
After wondering for a while why Fort Payne would be hotter than Tuscaloosa several days consecutively, I consulted Jason Simpson. It didn't take long for us to come up with a theory. It could be possible that the reason why Fort Payne was several degrees hotter than Tuscaloosa is because Fort Payne was under the influence of adiabatic heating because of its location in a valley, and Tuscaloosa was not. Now, this is just a theory, and other factors could have been involved, but this particular factor definitely could have contributed to the situation.
So how exactly could adiabatic heating effect this situation? Well, to begin with, adiabatic processes occur without a heat transfer between a system (such as a parcel of air) and its surrounding environment. The parcel of air can warm and cool adiabatically by changing the atmospheric pressure on the parcel. This is done by changing the altitude of the parcel. When a parcel of air rises, the pressure decreases, and the air expands and cools. When a parcel descends, the pressure increases, the air is compressed, and the parcel heats up. Both of these processes are common near mountain slopes.
So, it could be possible that the weather station at Isbell Field in Fort Payne recorded a higher temperature than the station in Tuscaloosa, because air moving down from Sand Mountain into the valley was compressed enough to raise the temperature by a few degrees. Unsaturated air has a lapse rate of about 5.5 degrees per 1000 feet, which means that a parcel that descends 1000 feet will have a 5.5 degree rise in temperature. So, it is probable that Fort Payne, at several hundred feet lower elevation than the station on Sand Mountain, definitely experienced higher temperatures because of adiabatically heated air. Tuscaloosa, on the other hand, has no change in elevation of that magnitude anywhere close, so adiabatic heating induced by topography would not be a factor.
So, that may be the reason why Fort Payne was a little bit hotter than Tuscaloosa for several days last week.
Drew McCombs
ABC 33/40 Weather Intern
abc3340wx2@gmail.com
on July 24, 2006, 10:57 pm
Josh Johnson
Reply to this comment