Enhance MET NetCDF library code to handle time variables of type byte.

[JohnHalleyGotway]

Describe the Enhancement

This issue arose when attempting to read a new dataset into MET in preparation for physics testing in HAFS. Kathryn Newman is the contact person for this work.

CYGNSS data (level 3 surface wind data) in NetCDF format can be found here:
https://podaac.jpl.nasa.gov/dataset/CYGNSS_L3_V2.1

The NetCDF level 3 data is gridded and is on a lat/lon grid... so no projection details with which to contend. I grabbed a sample data file and ran:

plot_data_plane cyg.ddmi.s20200803-003000-e20200803-233000.l3.grid-wind.a10.d21.nc wind_speed.ps 'name="wind_speed"; level="(0,*,*)";'
ERROR  : 
ERROR  : get_double_var() -> data type mismatch (double vs. "byte").
ERROR  : It won't be converted because of dimension issue.
ERROR  : Please correct the data type to double for variable "time".
ERROR  :

After running ncdump/ncgen to manually change the time variable from type byte to double, plot_data_plane reads this data just fine and produces this image:

This task is to enhance the NetCDF library support in MET to handle the time variable being defined as type byte directly. A sample input NetCDF data file is attached.
cyg.ddmi.s20200803-003000-e20200803-233000.l3.grid-wind.a10.d21.nc.txt

Time Estimate

1 day.

Sub-Issues

Consider breaking the enhancement down into sub-issues.
No sub-issues required.

Relevant Deadlines

NONE.

Funding Source

Define the source of funding and account keys here or state NONE.

Define the Metadata

Assignee

• Select engineer(s) or no engineer required: Howard
• Select scientist(s) or no scientist required: Kathryn

Labels

• Select component(s)
• Select priority
• Select requestor(s)

Projects and Milestone

• Review projects and select relevant Repository and Organization ones or add "alert:NEED PROJECT ASSIGNMENT" label
• Select milestone to next major version milestone or "Future Versions"

Define Related Issue(s)

Consider the impact to the other METplus components.

• METplus, MET, METdatadb, METviewer, METexpress, METcalcpy, METplotpy
  No impacts.

Enhancement Checklist

See the METplus Workflow for details.

• Complete the issue definition above, including the Time Estimate and Funding Source.
• Fork this repository or create a branch of develop.
  Branch name: feature_<Issue Number>_<Description>
• Complete the development and test your changes.
• Add/update log messages for easier debugging.
• Add/update unit tests.
• Add/update documentation.
• Push local changes to GitHub.
• Submit a pull request to merge into develop.
  Pull request: feature <Issue Number> <Description>
• Define the pull request metadata, as permissions allow.
  Select: Reviewer(s), Project(s), Milestone, and Linked issues
• Iterate until the reviewer(s) accept and merge your changes.
• Delete your fork or branch.
• Close this issue.

[hsoh-u]

It's done for attribute (get_att_unixtime at nc_var_info.cc), but not for the data variable.

[hsoh-u]

It's different from handling of an time attribute which contains the string of "yyyymmdd" form. The time variable at the sample data is 1 byte integer (not character).