Rate of change of some atmospheric variable. On these pages,
it refers to the change in temperature with altitude.
Normally expressed as the negative change in temperature per kilometer,
I have used values with the opposite sign.
Note - in the graph, the lapse rate lines have a slope of
one over the specified value ... this is because the lapse rate is change in
temperature over the change in height, and temperature is on the x-axis.
DALR - Dry Adiabatic Lapse Rate (-9.760 °C/km)
When a gas is compressed it gets warmer, when it expands it cools.
The Dry Adiabatic Lapse Rate is the change in temperature expected
when a parcel of air move up in the atmosphere to where the
pressure is lower.
SALR - Saturated Adiabatic Lapse Rate - aka
MALR - Moist Adiabatic Lapse Rate
This is the lapse rate when water changes phase.
This varies from about -3.0 °C/km to the DALR -
it varies with both temperature and pressure.
In the graph, the SALR line has a value of -4.
ELR - Environmental Lapse Rate
This is the actual measured change in temperature.
The standard (average, expected) in the troposphere
is -6.5 °C/km ... which is the value in the graph.
The graph includes both the 1964 and 1976 standards.
As you can see, the real atmosphere never looks like these.
Besides that atmosphere being much colder in the Tropopause,
the top of the Troposphere varies day to day, with the seasons,
and with latitude.
I just picked a few records that appeared to not have any clouds.
The data is collected at 00:00 UTC and 12:00 UTC of each day.
For Jacksonville, FL, (UTC -5:00) that corresponds
to 7:00 pm and 7:00 am respectively ...
ignoring daylight savings time.