# Example of CAPE & LI

Submitted by uk.sci.weather on Tue, 22/01/2008 - 4:59pm.

On this example (of a Skew T, log P diagram), CAPE is the area enclosed by: X - A - TOP - B - Y - X (shaded green); Lifted Index is given by the difference (observing the sign) between the temperature (B-A): see explanation below:.... |

A | The point (and associated temperature) where a saturated parcel given this particular ascent crosses the 500 hPa isobar=T(P) |

B | The actual temperature, T(500), from the radio-sonde ascent in this particular situation. The difference B-A [ or T(500) - T(P) gives the Lifted Index. |

X | The temperature at the surface (SFC) which initiated this particular parcel's ascent. From X to LFC, ascent-cooling will be at the Dry Adiabatic Lapse Rate (DALR). |

Y | The lowest 100 m or so of the ascent as given in the radio-sonde ascent; this will become heavily modified due to afternoon heating. |

LFC | The 'Level of Free Convection', above which the parcel, rising from the surface, will be saturated, and cool at the Saturated Adiabatic Lapse Rate (SALR), in this case from LFC to TOP. |

TOP | The point at which the temperature of the parcel=temperature of the environment, and buoyancy is neutral; the parcel theoretically ceases to rise of it's own volition - but given enough positive energy below this point, tops may (& often do) 'overshoot'. (also known as the 'Equilibrium Level') |