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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)  

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. 
 
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) 

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 3hour 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.  
ERA5Land 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) 

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 2^{nd} of the month to the 1^{st} 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 2^{nd} January of the year to 1^{st} January of the next year (inclusive).  
ERA5Land 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 t_{2 }is the day of interest, t_{1 }is the day before t2, tp_{t2} is the total precipitation at t2, and tp_{t1 }is the total precipitation at t1. 
where t_{2 }is the day of interest, t_{1 }is the day before t2, tp_{t2} is the total precipitation at t2, and tp_{t1 }is the total precipitation at t1. 
where t_{2} is the 1st day of the month after the month of interest, t_{1}= is the 1st day of month before t2, tp_{t2}= is the total precipitation at t2, and tp_{t1 }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 t_{1 }is the month of interest, N1 is the number of days in t_{1, }and tp_{t1 }is the result of (total precipitation at t_{1} * N1 * 24 * 60 * 60).  N/A For seasonal forecasts, as data only cover 7 months  
ERAInterim subdaily 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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