What does the notation "kg kg-1" for units mean for specific humidity?
I am using a data set from Justin Sheffield at Princeton that includes specific humidity. The description is as follows:
>"Reanalysis 6-hourly specific humidity interpolated to 1.0deg with account for elevation changes and scaled to maintain consistency with reanalysis relative humidity and CRU TS3.0 monthly air temperature";
The units are = "kg kg-1"
What does this mean? Does it mean kg/kg so essentially dimensionless? Because I have seen around specific humidity measured also in g/kg, maybe that was wrong?
These two pages give the same definition of specific and absolute humidity, I thought they were different things:
Specifying kg/kg or (g water)/(kg air) indicates that the humidity is by mass rather than volume. Because water vapor is less dense than dry air, kg/kg gives a value about 62% of the humidity by volume.