I see similar flavours of this question have been asked a few times, but I still don't see a satisfying answer. I am looking for data (maps) of the earth subsurface temperature at a depth sufficient to consider the temperature more or less constant (let's say in a range of ±5% ?). I am looking for data for:
- Latitude: for polar, temperate and equatorial latitudes
- Time of the year: per season or per month
- Time of day: at noon and midnight
Where can I find publicly available (free) data for this?