Lapse Rate = -dT/dh The negative of the change in temperature divided by the change in height
For scientific purposes, the lapse rate is expressed as
On these pages, I prefer to use the incorrect change in temperature with height which provides a negative value when the temperature decreases with height. (By definition, Lapse Rate is a positive value.)
|SALR||-4.9||-2.7||Variable, -3 to -9.8|
|3.0||1.6||Warmer with height|
|Lower||1.0||0.55||Warmer with height|
|Upper||2.8||1.5||Warmer with height|
I have provided several interactive graphs to help demonstrate these concepts.
|Seasons||This compares the seasons - winter, spring, summer - and has notes explaining DALR, SALR, ELR|
|Winter||2 days in February|
|Summer||4 days in August|
Additional user interface features
The data comes from noaa - just navigate using
Maps/Charts / By Station / United States / Jacksonville
The data files are typically for 00:00 UTC and 12:00 UTC.
(The standard collection times are 0000, 0600, 1200, 1800 UTC.)
Because Jacksonville is 5 hours earlier, these should
This means that the DALR (Dry Adiabatic Lapse Rate = 9.8°C/km) has a slope of
1/(-9.8°C/km) = -0.10km/°C
The SALR varies from about 3°C/km to the DALR (9.8°C/km), depending on the temperature, pressure, and humidity. In the graphs, it is shown as having a slope of
1/(-4.0°C/km) = -0.25km/°C
When you actually measure the temperature at various heights, the average slope is between the DALR and the SALR. By international agreement, the ELR is 6.5°C/km. One of the reasons for providing adjustable lapse rate lines is so that you can see how close the ELR is to the measured values.
The graphs also let you see that the surface and tropopause temperatures differ significantly from the standard model. This was a consideration in selecting those specific data sets.
The tropopause is interesting - by definition, the temperature is constant, but that is seldom observed. Both the height and thickness of the tropopause varies with season and latitude.