Lifting condensation level zone
From AMS Glossary
lifting condensation level zone
(Abbreviated LCL zone.) The range of altitudes within which the lifting condensation level (LCL) occurs for different air parcels rising from near the surface.
Due to natural variability and land-use heterogeneity, air parcels at different horizontal locations near the ground usually have slightly different temperatures and humidities. As a result, each air parcel has its own LCL. Over a town, for example, LCLs might vary from 1000 m over an irrigated park to 1400 m over a paved parking area, thus giving a 400 m thick LCL zone centered at 1200 m. This implies that cumulus clouds formed from rising surface-layer air will have slightly different cloud-base altitudes within a region. While it is difficult to see this effect when observed from the ground, it is very obvious to aircraft flying at the average cloud-base altitude.