What is the sea level temperature in degrees Celsius as defined by standard atmosphere?

In the context of the standard atmosphere, the sea level temperature is defined as 15 degrees Celsius. This value is part of the International Standard Atmosphere (ISA), which provides a consistent framework for understanding atmospheric conditions at sea level and helps in various calculations and flight operations. The ISA assumes that at sea level, the temperature is 15 degrees Celsius along with a specific pressure of 1013.25 hPa (hectopascals). This standardization helps in the analysis and predictions of aircraft performance, weather patterns, and other atmospheric phenomena crucial for aviation and meteorology.