Bulk mixed layer model
From AMS Glossary
bulk mixed layer model
(Abbreviated bulk ML model.) An idealized model of the atmospheric mixed layer that assumes uniform values of variables within the ML, with sharp jumps or discontinuities across the top.
For midlatitude, fair-weather situations over land, the ML values are usually cooler in potential temperature, slower in wind speed, and higher in humidity than air in the free atmosphere just above the ML.