id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
356	Added capability to process the add_offset attribute in input NetCDF files	arango	arango	"Added code in the NetCDF input routines to process the '''add_offset''' attribute, if present in an input NetCDF variable. This implies that users need to be careful when including such an attribute in a NetCDF variable.

If the '''add_offset''' attribute is present for a variable, its numeric value is added to the data after is read by ROMS I/O interface. In some applications, the '''add_offset''' is used to provide simple data compression. Also, it can be used to change units. For example, we can convert temperature from Kelvin to Celsius:

{{{
        float Tair(time, eta_rho, xi_rho) ;
                Tair:long_name = ""surface air temperature"" ;
                Tair:units = ""Celsius"" ;
                Tair:add_offset = -273.16;
                Tair:time = ""time"" ;
}}}

Here the original data is actually in Kelvin, so a value of '''-273.16''' is added to the data to convert it to Celsius.

Many thanks to Kate Hedstrom for suggesting this capability."	upgrade	closed	major	Release ROMS/TOMS 3.3	Nonlinear	3.3	Done