Which hPa value corresponds to ground level (0 feet ASL)?

The value of 1,013 hPa is widely recognized as standard atmospheric pressure at sea level, which is equivalent to 0 feet above sea level (ASL). This is based on the International Standard Atmosphere (ISA), which provides a baseline for atmospheric conditions. In meteorological terms, 1,013 hPa corresponds to the pressure exerted by the weight of the atmosphere at sea level.

As altitude increases, atmospheric pressure decreases, so the values of 500 hPa, 200 hPa, and 850 hPa represent pressures at higher altitudes rather than at ground level. For instance:

• 500 hPa is typically found around 18,000 feet ASL.
• 850 hPa generally corresponds to an altitude of approximately 5,000 feet ASL, where the air is noticeably less dense than at sea level.
• 200 hPa is even higher, often reaching altitudes around 39,000 feet ASL.

Thus, 1,013 hPa at ground level serves as an important reference point for pilots and meteorologists, allowing them to assess conditions and altitude more accurately.