From Glossary of Meteorology
(Abbreviated mts system.) A system of physical units based upon the use of the meter, the metric ton (or tonne: 106 grams), and the second as elementary quantities of length, mass, and time, respectively.
In this system, density is expressed in tonne m-3, velocity or speed in m s-1, force in tonne m-2 (or sthene), pressure in centibars (or pieze), and energy in kilojoules. The mts system is used primarily by European engineers.