Lifted Index

Introduction to Lifted Index

The Lifted Index (LI) is a measure of atmospheric instability. It is calculated by finding the temperature difference, in degrees Celsius, between the temperature at 850mb (around 1.5km above the surface) and the temperature at the level of free convection (LFC). In this formula, LI represents the Lifted Index, T850 represents the temperature at 850mb, and T_LFC represents the temperature at the level of free convection.

Parameter usage:

• temp850 = temperature at 850mb (°C)
• temp500 = temperature at 500mb (°C), not used directly in the formula
• tempLFC = temperature at the level of free convection (LFC) (°C)
• pressureLFC = pressure at the level of free convection (LFC) (mb)

Data validation

The temperature values should be provided in degrees Celsius. The pressure at the level of free convection (LFC) should be provided in millibars (mb).

Summary

The Lifted Index is used in meteorology to assess the potential for severe weather. Positive values typically indicate stable, non-severe conditions, while increasingly negative values indicate greater potential for severe weather such as thunderstorms or hail.