A character string indicating a unit. Case is ignored, so that e.g.
"dbar"
and "DBAR"
yield equal results. The following are recognized:
c("m-1"
, "dbar"
, "decibar"
, "degree"
, "degree_Celcius"
,
"degree_north"
, "degree_east"
, "ipts-68"
,
"its-90"
, "m/s^1"
, "m/s^2"
, "pss-78"
,
"umol/kg"
, "micromole/kg"
)