Question about coastal grid cells in ERA5 wave data

Datasets and Usage C3S - Datasets and Usage
1

Hello,

I have a question about ERA5 wave data (significant wave height, wave period) near the coast.

Suppose I select a point in the ocean that belongs to a 0.5° × 0.5° grid cell, and part of that cell extends over land. My question is:

  • If the center of the grid cell is over the ocean, does ERA5 compute the wave variables ignoring the land portion, so that the value corresponds only to the ocean?

  • Or does the presence of land in the cell affect the wave height (for example, artificially lowering it or setting Hs = 0)?

Thank you very much for your help!

2

Hi
please have a look at this post: ERA5 Wave HRES native grid exact coordinates - #6 by Jean_Bidlot

Thanks

3

Hi,

Thanks for the link to the article about the ERA5 Wave HRES native grid. I have read it, and it explains the grid coordinates well.

However, my question is about how wave values are handled in coastal grid cells:

  • If a 0.5° (or 0.36° native) grid cell has its center over the ocean but part of the cell extends over land, does ERA5:

    1. Ignore the land portion and return wave height only for the ocean?

    2. Or does the land influence the computed wave height (e.g., Hs = 0 or artificially reduced)?

I am aware of the grid coordinates, but I need clarification on the physics/processing near coasts.

Thanks in advance for your clarification!