Published on 2025/08/25
Originally finished on 2024/10/03

Note: This method is not the most efficient, unless you would need large chunks of data. For downloading anything shorter than a whole month, I would actually recommend downloading using the cdsapi module in python as a script or actually use the CDS portal. You can download about 11 days of data on pressure levels in one go, and even more for data on the surface level. (I am planning to write more on that later.) This article is thus provided as-is and for your reference only.

Although NCAR’s repository for ERA5 data in grib was phased out, the data can still be somehow obtained here as for now: TDS Catalog.

ERA5 has different categories like surface (SFC) and pressure level (PL). They do not need to be separated to two streams of initial conditions.

Also, the variable LANDSEA which is a binary mask, is located in ERA5’s invariant category. If it is not downloaded and ungrib-ed, MPAS will complain:

ERROR: ********************************************************************************
ERROR: LANDSEA field not found in meteorological data file ERA5PL:2023-04-22_00
CRITICAL ERROR: ********************************************************************************
Logging complete.  Closing file at 2024/10/03 14:33:39

Check the Vtable for ERA5:

GRIB | Level| Level| Level| metgrid  |  metgrid | metgrid                                  |
Code | Code |   1  |   2  | Name     |  Units   | Description                              |
-----+------+------+------+----------+----------+------------------------------------------+
 129 | 100  |   *  |      | GEOPT    | m2 s-2   |                                          |
     | 100  |   *  |      | HGT      | m        | Height                                   |
 130 | 100  |   *  |      | TT       | K        | Temperature                              |
 131 | 100  |   *  |      | UU       | m s-1    | U                                        |
 132 | 100  |   *  |      | VV       | m s-1    | V                                        |
 157 | 100  |   *  |      | RH       | %        | Relative Humidity                        |
 165 |  1   |   0  |      | UU       | m s-1    | U                                        | At 10 m
 166 |  1   |   0  |      | VV       | m s-1    | V                                        | At 10 m
 167 |  1   |   0  |      | TT       | K        | Temperature                              | At 2 m
 168 |  1   |   0  |      | DEWPT    | K        |                                          | At 2 m
     |  1   |   0  |      | RH       | %        | Relative Humidity                        | At 2 m
 172 |  1   |   0  |      | LANDSEA  | 0/1 Flag | Land/Sea flag                            |
 129 |  1   |   0  |      | SOILGEO  | m2 s-2   |                                          |
...

GRIB Code for Land/Sea flag is 172.

(https://thredds.rda.ucar.edu/thredds/catalog/files/g/d633000/e5.oper.invariant/197901/catalog.html)

It is in the invariant field.