3.27 ARM Conventions

Availability: ncrcat Short options: None

ncrcat has been programmed to correctly handle data files which utilize the Atmospheric Radiation Measurement (ARM) Program convention for time and time offsets. If you do not work with ARM data then you may skip this section. ARM data files store time information in two variables, a scalar, base_time, and a record variable, time_offset. Subtle but serious problems can arise when these type of files are just blindly concatenated. Therefore ncrcat has been specially programmed to be able to chain together consecutive ARM input-files and produce and an output-file which contains the correct time information. Currently, ncrcat determines whether a datafile is an ARM datafile simply by testing for the existence of the variables base_time, time_offset, and the dimension time. If these are found in the input-file then ncrcat will automatically perform two non-standard, but hopefully useful, procedures. First, ncrcat will ensure that values of time_offset appearing in the output-file are relative to the base_time appearing in the first input-file (and presumably, though not necessarily, also appearing in the output-file). Second, if a coordinate variable named time is not found in the input-files, then ncrcat automatically creates the time coordinate in the output-file. The values of time are defined by the ARM conventions time = base_time + time_offset. Thus, if output-file contains the time_offset variable, it will also contain the time coordinate. A short message is added to the history global attribute whenever these ARM-specific procedures are executed.