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DatasetVariablesWhat it isGrib unitsNetcdf UnitsTo 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 precipitationAccumulations are over the hour (the processing period) ending at the validity date/timem (of water equivalent per hour)m (of water equivalent per hour)

Mathdisplay
\text{tp}\ [\text{mm}] = \text{tp}\ [\text{m}] \cdot 1000

Total precipitation over the one hour ending at forecast step.

Mathinline
\text{tp}\ [\text{mm}] = \left( \sum_{h = 1}^{23}\text{tp}_{h}\ [\text{m}] + \text{tp}_{d+1\  00\text{UTC}}\ [\text{m}] \right) \cdot 1000

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.

Mathinline
\text{tp}\ [\text{mm}] =  \sum_{n = 1}^{N} \left( \sum_{h = 1}^{23}\text{tp}_{h}\ [\text{m}] + \text{tp}_{d+1\  00\text{UTC}}\ [\text{m}] \right)_{n} \cdot 1000

where N is the number of days in the month.

Mathinline
\text{tp}\ [\text{mm}] =  \sum_{n = 1}^{N} \left( \sum_{h = 1}^{23}\text{tp}_{h}\ [\text{m}] + \text{tp}_{d+1\  00\text{UTC}}\ [\text{m}] \right)_{n} \cdot 1000
where N is the number of days in the year.
ERA5 ensemble members (3 hourly data)Total precipitationAccumulations are over the 3 hours (the processing period) ending at the validity date/timem (of water equivalent per 3 hours)m (of water equivalent per 3 hours)

Mathinline
\text{tp}\ [\text{mm}] = \text{tp}\ [\text{m}] \cdot 1000

Mathinline
\text{tp}\ [\text{mm}] =
\left( \sum_{h} \text{tp}_{h} [\text{m}] \right) \cdot 1000   

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.

Mathinline
\text{tp}\ [\text{mm}] =
\sum_{n = 1}^{N} \left(\sum_{h} \text{tp}_{h}[\text{m}] \right)_{n} \cdot 1000   

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.

Mathinline
\text{tp}\ [\text{mm}] =
\sum_{n = 1}^{N} \left(\sum_{h} \text{tp}_{h}[\text{m}] \right)_{n} \cdot 1000   

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 precipitationThe 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/AN/A

Mathinline
\text{tp}\ [\text{mm}] = \text{tp}\ [\text{m/day}] \cdot 1000 \cdot N

where N is the number of days in the month.

Mathinline
\text{tp}\ [\text{mm}] = \sum_{n = 1}^{12}(\text{tp}\ [\text{m/day}] \cdot 1000 \cdot N)_{\text{n}}

where N is the number of days in the month and n is the number of the month.

ERA5 monthly averaged ensemble members
Total precipitationThe 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/AN/A

Mathinline
\text{tp}\ [\text{mm}] = \text{tp}\ [\text{m/day}] \cdot 1000 \cdot N

where N is the number of days in the month.

Mathinline
\text{tp}\ [\text{mm}] = \sum_{n = 1}^{12}(\text{tp}\ [\text{m/day}] \cdot 1000 \cdot N)_{\text{n}}

where N is the number of days in the month and n is the number of the month.

ERA5-Land hourly dataTotal precipitation

Accumulations are from 00 UTC to the hour ending at the forecast step 1

m (of water equivalent)m (of water equivalent)

Mathinline
\text{tp}\ [\text{mm}] = \left\{
\begin{array}{ll}
\text{tp}_{h}\ [\text{m}] \cdot 1000 & h = 01 \text {UTC} \\
(\text{tp}_{h}\ [\text{m}]\ -\ \text{tp}_{h-1}\ [\text{m}])\ \cdot 1000 & \text{otherwise} \\
\end{array}
\right.

Mathinline
\text{tp}\ [\text{mm}] = \text{tp}_{d+1\  00\text{UTC}}\ [\text{m}]\ \cdot 1000

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.

Mathinline
\text{tp}\ [\text{mm}] = \left( \sum_{n = 1}^{N}\text{tp}_{d+1\ 00\text{UTC},n}\ [\text{m}] \right)\cdot 1000

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).

Mathinline
\text{tp}\ [\text{mm}] = \left( \sum_{n = 1}^{N}\text{tp}_{d+1\ 00\text{UTC},n}\ [\text{m}] \right) \cdot 1000

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 dataTotal 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/AN/A

Mathinline
\text{tp}\ [\text{mm}] = \text{tp}\ [\text{m/day}] \cdot 1000 \cdot N

where N is the number of days in the month.

Mathinline
\text{tp}\ [\text{mm}] = \sum_{n = 1}^{12}(\text{tp}\ [\text{m/day}] \cdot 1000 \cdot N)_{\text{n}}

where N is the number of days in the month and n is the number of the month.

Seasonal daily dataTotal precipitation24 hour aggregation since the beginning of the forecastmm

Mathinline
\text{tp}\ [\text{mm/hr}] = \frac{(\text{tp}_{t2}\ [\text{m}] - \text{tp}_{t1}\ [\text{m}])\cdot 1000}{24}

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.

Mathinline
\text{tp}\ [\text{mm}] = (\text{tp}_{t2}\ [\text{m}] - \text{tp}_{t1}\ [\text{m}])\cdot 1000

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.

Mathinline
\text{tp}\ [\text{mm}] = (\text{tp}_{t_2}\ [\text{m}] - \text{tp}_{t_1}\ [\text{m}])\cdot 1000

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 dataTotal precipitation

The accumulations in monthly means have units that include "per second".

m/sm/sN/AN/A

Mathinline
\text{tp}\ [\text{mm}] = \text{tp}_{t1}\ [\text{m}]\cdot 1000

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 precipitationAccumulations are from the beginning of the forecastm (of water equivalent)m (of water equivalent)

N/A

NOT AVAILABLE HOURLY

Mathinline
\text{tp}\ [\text{mm}] = (\text{tp}_{12\  00\text{UTC}}\ + \text{tp}_{12\  12\text{UTC}}\ [\text{m}])\ \cdot 1000

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.

Mathinline
\text{tp}\ [\text{mm}] = \sum_{d = 1}^{N}(\text{tp}_{12\  00\text{UTC}}\ + \text{tp}_{12\  12\text{UTC}}\ [\text{m}])_{d} \cdot 1000

where d is the day for which the total precipitation is being computed and N is the number of days in the month.

Mathinline
\text{tp}\ [\text{mm}] = \sum_{d = 1}^{N}(\text{tp}_{12\  00\text{UTC}}\ + \text{tp}_{12\  12\text{UTC}}\ [\text{m}])_{d} \cdot 1000

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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