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Mean rate parameters in ERA5 (e.g. Table 4) provide similar information to accumulations (Table 3), over the same processing periods, but they have different units which include except that they are expressed as temporal averages instead of accumulations, and so have units of "per second".
- Mean rate parameters are easier to deal with than accumulations because the units do not vary with the processing period.
- The mean rate hydrological parameters (e.g. the "Mean total precipitation rate") have units of "kg m-2 s-1", which are equivalent to "mm s-1". If you multiply by 86400 seconds (24 hours) you will produce the commonly used units of "mm day-1".
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