Downloading and processing ERA5 atmos forcing for HRLDAS/Noah-MP

[cenlinhe]

Currently, the HRLDAS_forcing pre-processing scripts/package only works with ERA5-Land not ERA5 atmosphere single layer data. The instruction is here: https://github.com/NCAR/hrldas/blob/master/hrldas/docs/README.ERA5
A step-by-step tutorial documentation will be developed soon.

ERA5-Land data can be download from the website:
https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-land?tab=form

There are examples of python API in the website.
https://confluence.ecmwf.int/display/CKB/ERA5-Land%3A+data+documentation#ERA5Land:datadocumentation-Dataorganisationandaccess

The atmospheric forcing data needs to be downloaded as grib file format.
The landsea mask and terrain must be downloaded as netcdf format, which is downloaded in the following website by clicking variable name in Table 1
https://confluence.ecmwf.int/display/CKB/ERA5-Land%3A+data+documentation#ERA5Land:datadocumentation-parameterlistingParameterlistings

Also, make sure all downloaded climate longitudes are between 0 and 360 degrees which has the same lat/lon as shown in geopotential and land mask NetCDF files. This is the default download in the website as Geographical area is set to Whole available region:
https://cds.climate.copernicus.eu/cdsapp#!/dataset/reanalysis-era5-land?tab=form