Final answer:
Typically, a temperature of 100 degrees Celsius is not encountered in the Earth's atmosphere and could only be found in extreme conditions or near volcanic activity. A temperature of 50 degrees Celsius could be possible near the Earth's surface in extremely hot desert areas, like Death Valley.
Step-by-step explanation:
The question involves the concept of atmospheric temperature gradients as we ascend from the Earth's surface into the upper layers of the atmosphere. Specifically, it's dealing with the temperatures at which water boils (100 degrees Celsius) and an intermediate temperature (50 degrees Celsius) relative to altitude.
However, it's important to clarify that the temperature doesn't uniformly increase or decrease with altitude in a simple manner—as we first go higher, the temperature generally decreases in the troposphere, then may increase in the stratosphere due to ozone absorption of UV radiation, and so forth. Therefore, encountering temperatures of 100 degrees Celsius or 50 degrees Celsius at specific altitudes is not a usual circumstance in Earth's atmosphere under normal conditions and would likely only be found near the surface in extremely hot environments or artificially within human-made structures like a spacecraft during re-entry.
To answer the first part of the question -- you typically would not encounter a natural air temperature of 100 degrees Celsius unless near volcanic activity or in unusual, extreme conditions. As for the second part, finding a temperature of 50 degrees Celsius in the atmosphere could be possible close to the Earth's surface in very hot desert regions. To provide an example, the highest recorded air temperature on Earth is 56.7 degrees Celsius in Death Valley, California, at the surface level.