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Dataset | Variables | What it is | Grib units | Netcdf Units | To get the total precipitation for an hour (mm) | To get the total precipitation for a day (mm) | To get the total precipitation for a month (mm) | To get the total precipitation for a year (mm) | ||||||||
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ERA5 reanalysis (hourly data) | Total precipitation | Accumulations are over the hour (the processing period) ending at the validity date/time | m (of water equivalent per hour) | m (of water equivalent per hour) |
Total precipitation over the one hour ending at forecast step. |
where h is the hour and d the day of interest (d+1 is the following day). The total precipitation over 24 hours is the sum of the individual total precipitation values for each hour. |
where N is the number of days in the month. |
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ERA5 ensemble members (3 hourly data) | Total precipitation | Accumulations are over the 3 hours (the processing period) ending at the validity date/time | m (of water equivalent per 3 hours) | m (of water equivalent per 3 hours) |
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where h are the day timesteps available: 03 UTC, 06 UTC, 09 UTC, 12 UTC, 15 UTC, 18 UTC, 21 UTC and 00 UTC of the day after. The total precipitation over 24 hours is the sum of 8 3-hour total precipitation values. |
where h are the day timesteps available: 03 UTC, 06 UTC, 09 UTC, 12 UTC, 15 UTC, 18 UTC, 21 UTC and 00 UTC of the day after and N is the number of days in the month. |
where h are the day timesteps available: 03 UTC, 06 UTC, 09 UTC, 12 UTC, 15 UTC, 18 UTC, 21 UTC and 00 UTC of the day after, and N is the number of days in the year. | ||||||||
ERA5 monthly averaged reanalysis | Total precipitation | The accumulations in monthly means of daily means have been scaled to have units that include "per day" | m (of water equivalent per day) | m (of water equivalent per day) | N/A | N/A |
where N is the number of days in the month. |
where N is the number of days in the month and n is the number of the month. | ||||||||
ERA5 monthly averaged ensemble members | Total precipitation | The accumulations in monthly means of daily means have been scaled to have units that include "per day" | m (of water equivalent per day) | m (of water equivalent per day) | N/A | N/A |
where N is the number of days in the month. |
where N is the number of days in the month and n is the number of the month. | ||||||||
ERA5-Land hourly data | Total precipitation | Accumulations are from 00 UTC to the hour ending at the forecast step 1 | m (of water equivalent) | m (of water equivalent) |
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where d is the day for which the average flux total precipitation is being computed. The time step labelled d+1 00UTC should also be taken because it contains the accumulated flux total precipitation over the previous 24 hours. |
where d is the day for which the total precipitation is being computed and N is the number of days in the month. The time step labelled d+1 00UTC should also be taken because it contains the accumulated total precipitation over the previous 24 hours. This implies that the sum goes from the 2nd of the month to the 1st of the next month (inclusive). |
where d is the day for which the total precipitation is being computed and N is the number of days in the year. The time step labelled d+1 00UTC because it contains the accumulated total precipitation over the previous 24 hours. This implies that the sum goes from 2nd January of the year to 1st January of the next year (inclusive). | ||||||||
ERA5-Land monthly averaged data | Total precipitation | The accumulations in monthly means of daily means have units that include "per day". | m (of water equivalent per day) | m (of water equivalent per day) | N/A | N/A |
where N is the number of days in the month. |
where N is the number of days in the month and n is the number of the month. | ||||||||
Seasonal daily data | Total precipitation | 24 hour aggregation since the beginning of the forecast | m | m |
where t2 is the day of interest, t1 is the day before t2, tpt2 is the total precipitation at t2, and tpt1 is the total precipitation at t1. |
where t2 is the day of interest, t1 is the day before t2, tpt2 is the total precipitation at t2, and tpt1 is the total precipitation at t1. |
where t2 is the 1st day of the month after the month of interest, t1= is the 1st day of month before t2, tpt2= is the total precipitation at t2, and tpt1 is the total precipitation at t1. | N/A For seasonal forecasts, as data only cover 7 months | ||||||||
Seasonal Monthly data | Total precipitation | The accumulations in monthly means have units that include "per second". | m/s | m/s | N/A | N/A |
where t1 is the month of interest, N1 is the number of days in t1, and tpt1 is the result of (total precipitation at t1 * N1 * 24 * 60 * 60). | N/A For seasonal forecasts, as data only cover 7 months | ||||||||
ERA-Interim sub-daily data | Total precipitation | Accumulations are from the beginning of the forecast | m (of water equivalent) | m (of water equivalent) | N/A NOT AVAILABLE HOURLY |
where the time step labelled 12 has to be selected from time reference 00UTC plus the time step labelled 12 selected from time reference 12UTC because they contain the accumulated total precipitation over the 24 hours for each day. |
where d is the day for which the total precipitation is being computed and N is the number of days in the month. |
where d is the day for which the total precipitation is being computed and N is the number of days in the year. |
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1 Please, note that the convention for accumulations used in ERA5-Land differs with that for ERA5. The accumulations in the short forecasts of ERA5-Land (with hourly steps from 01 to 24) are treated the same as those in ERA-Interim or ERA-Interim/Land, i.e., they are accumulated from the beginning of the forecast to the end of the forecast step. For example, runoff at day=D, step=12 will provide runoff accumulated from day=D, time=0 to day=D, time=12. The maximum accumulation is over 24 hours, i.e., from day=D, time=0 to day=D+1,time=0 (step=24).
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This document has been produced in the context of the Copernicus Climate Change Service (C3S). The activities leading to these results have been contracted by the European Centre for Medium-Range Weather Forecasts, operator of C3S on behalf of the European Union (Delegation agreement Agreement signed on 11/11/2014 and Contribution Agreement signed on 22/07/2021). All information in this document is provided "as is" and no guarantee or warranty is given that the information is fit for any particular purpose. The users thereof use the information at their sole risk and liability. For the avoidance of all doubt , the European Commission and the European Centre for Medium - Range Weather Forecasts have no liability in respect of this document, which is merely representing the author's view. |
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