Thanks,
MM43 and
PJ2 for your most elucidating inputs.
Chris; Figure 11 of
Tim Vasquez' analysis shows the temperature profile of the atmosphere up to the tropopause and beyond, up to FL 700, and the temperature inside the CB. The temperature profile is obtained from a balloon ascent from Fernando de Noronha. I thought this provides some good background to some of your questions/remarks.
Regards,
HN39