The NCEP model only provides atmospheric profile layers to about 16km (highest layer will vary) but MODTRAN considers "space" to be 100km. To approximate the highest layers of the atmosphere, a "standard" atmospheric profile is used. The Atmospheric Correction Parameter Calculator has two standard atmosphere available, mid-latitude summer and mid-latitude winter. The profiles for pressure, temperature and relative humidity are shown below for each.

The Atmospheric Correction Parameter Calculator uses all the atmospheric profile layers from the NCEP profiles and then pastes any higher layers of the selected standard atmosphere on top.

mid-latitude summer profiles mid-latitude winter profiles