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DatasetVariablesWhat it isGrib unitsNetcdf Units

To get the average energy flux (Wm-2)

To get the average energy flux for a day (Wm-2)To get the average energy flux for a month (Wm-2)To get the average energy flux for a year (Wm-2)
ERA5 daily data

Surface Solar Radiation (SSR)

Accumulations are over the hour (the processing period) ending at the forecast step

Jm-2

Jm-2


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \text{SSR}\ [\text{Jm}^{-2}]\ /\ 3600\ [\text{s}]


Average flux over the one hour ending at forecast step.


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \frac{ \sum_{h = 0}^{23} \text{SSR}_{h}\ [\text{Jm}^{-2}] + \text{SSR}_{d+1 00\text{UTC}}\ [\text{Jm}^{-2}]}{86400\ [\text{s}]}


The average flux over 24 hours is the sum of the individual fluxes for each hour divided by the number of seconds in a day.


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \frac{\sum_{n = 1}^{N} \left( \sum_{h = 0}^{23} \text{SSR}_{h}\ [\text{Jm}^{-2}] + \text{SSR}_{d+1 00\text{UTC}}\ [\text{Jm}^{-2}] \right)_{n}}{N \cdot 86400\ [\text{s}]}

where N is the number of days in the month.

The average flux over a month is the sum of the individual fluxes for each day divided by the number of seconds in the month.


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \frac{\sum_{n = 1}^{N} \left( \sum_{h = 0}^{23} \text{SSR}_{h}\ [\text{Jm}^{-2}] + \text{SSR}_{d+1 00\text{UTC}}\ [\text{Jm}^{-2}] \right)_{n}}{N \cdot 86400\ [\text{s}]}

where N is the number of days in the year.

The average flux over a year is the sum of the individual fluxes for each day divided by the number of seconds in the year.


ERA5 daily ensemble data

SSR

Accumulations are over the 3 hours (the processing period) ending at the forecast stepJm-2Jm-2


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \text{SSR}\ [\text{Jm}^{-2}]\ /\ (3 \cdot 3600)\ [\text{s}]


Average flux over the three hours ending at forecast step.


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = 
\left( \sum_{h} \text{SSR}_{h}[\text{Jm}^{-2}] + \text{SSR}_{d+1 00\text{UTC}}\ [\text{Jm}^{-2}] \right) / 86400


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 average flux over 24 hours is the sum of 8 3-hour fluxes divided by the number of seconds in a day.


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = 
\sum_{n = 1}^{N} \left( \sum_{h} \text{SSR}_{h} [\text{Jm}^{-2}] + \text{SSR}_{d+1 00\text{UTC}}\ [\text{Jm}^{-2}] \right)_{n} / N \cdot 86400


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.

The average flux over a month is the sum of the individual fluxes for each day (computed as the sum of 8 3-hour fluxes) divided by the number of seconds in the month.


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = 
\sum_n = 1}^{N}\left( \sum_{d = 1}^{N} \sum_{h} \text{SSR}_{h} \right)_{n} / N \cdot 86400


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.

The average flux over a year is the sum of the individual fluxes for each day (computed as the sum of 8 3-hour fluxes) divided by the number of seconds in the year.


ERA5 monthly averaged data

SSR

Monthly means of mean daily fluxes

The accumulations in monthly means of daily means have been scaled to have units that include "per day"

Jm-2Jm-2N/AN/A


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] =  \text{SSR}\ [\text{Jm}^{-2}]\ \cdot \frac{N}{N\cdot 86400}\ [\text{s}] = \frac{\text{SSR}\ [\text{Jm}^{-2}]}{86400\ [\text{s}]}


where N is the number of days in the month.

  1. Multiply by N to obtain total monthly flux from mean daily flux
  2. Divide by number of seconds in the month


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \frac{ \sum_{m = 1}^{12}  \text{SSR}_{m}\ [\text{Jm}^{-2}]\ \cdot N_{m}}{D\cdot 86400\ [\text{s}]}


where Nm is the number of days in the month m, and D is the number of days in the year.

  1. Multiply each value by the number of days in the month
  2. Sum them together
  3. Divide by number of seconds in the year

ERA5 monthly averaged ensemble dataSSR

Monthly means of mean daily fluxes

The accumulations in monthly means of daily means have been scaled to have units that include "per day"

Jm-2Jm-2

N/A


N/A


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] =  \text{SSR}\ [\text{Jm}^{-2}]\ \cdot \frac{N}{N\cdot 86400}\ [\text{s}] = \frac{\text{SSR}\ [\text{Jm}^{-2}]}{86400\ [\text{s}]}

where N is the number of days in the month.

  1. Multiply by N to obtain total monthly flux from mean daily flux
  2. Divide by number of seconds in the month


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \frac{\sum_{m = 1}^{12}  \text{SSR}_{m}\ [\text{Jm}^{-2}]\ \cdot N_{m}}{D\cdot 86400\ [\text{s}]}

where Nm is the number of days in the month m, and D is the number of days in the year.

  1. Multiply each value by the number of days in the month
  2. Sum them together
  3. Divide by number of seconds in the year

ERA5-Land hourly data

SSR

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

Footnote

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).


Jm-2Jm-2


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \left\{
\begin{array}{ll}
    \frac{\text{SSR}_{h}\ [\text{Jm}^{-2}]}{3600\ [\text{s}]} & h = 01 \text {UTC} \\
    \frac{\text{SSR}_{h}\ [\text{Jm}^{-2}]\ -\ \text{SSR}_{h-1}\ [\text{Jm}^{-2}]}{3600\ [\text{s}]} & \text{otherwise} \\
\end{array} 
\right.



Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \frac{\text{SSR}_{d+1\ 00\text{UTC}}\ [\text{Jm}^{-2}]}{86400\ [\text{s}]}


where d is the day for which the average flux is being computed.

The time step labelled d+1 00UTC is selected because it contains the accumulated flux over the previous 24 hours.


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \frac{\sum_{d = 1}^{N}\text{SSR}_{d+1\ 00\text{UTC}}\ [\text{Jm}^{-2}]}{N\cdot 86400\ [\text{s}]}


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

The time step labelled d+1 00UTC because it contains the accumulated flux 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{SSR}\ [\text{Wm}^{-2}] = \frac{\sum_{d = 1}^{N}\text{SSR}_{d+1\ 00\text{UTC}}\ [\text{Jm}^{-2}]}{N\cdot 86400\ [\text{s}]}


where d is the day for which the average flux 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 flux 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

SSR

Accumulations are created from data with a forecast period falling within the month. Monthly means of daily means for accumulations are created from the last forecast step (24) of the forecasts for each day of the month.

The accumulations in monthly means of daily means have been scaled to have units that include "per day"

Jm-2Jm-2N/AN/A


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] =  \text{SSR}\ [\text{Jm}^{-2}]\ \cdot \frac{N}{N\cdot 86400}\ [\text{s}] = \frac{\text{SSR}\ [\text{Jm}^{-2}]}{86400\ [\text{s}]}


where N is the number of days in the month.

  1. Multiply by N to obtain total monthly flux from mean daily flux
  2. Divide by number of seconds in the month


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \frac{ \sum_{m = 1}^{12}  \text{SSR}_{m}\ [\text{Jm}^{-2}]\ \cdot N_{m}}{D\cdot 86400\ [\text{s}]}


where Nm is the number of days in the month m, and D is the number of days in the year.

  1. Multiply each value by the number of days in the month
  2. Sum them up
  3. Divide by number of seconds in the year

Seasonal daily dataSSR24 hour aggregation since the beginning of the forecastJm-2Jm-2N/A


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \frac{(\text{SSR}_{t2}\ [\text{Jm}^{-2}] - \text{SSR}_{t1}\ [\text{Jm}^{-2}])}{24*60*60}


where t2 is the day of interest, t1 is the day before t2, SSRt2 is the SSR at t2, and SSRt1 is the SSR at t1


Mathinline
\text{SSR}\ [\text{Wm}^{-2}] = \frac{(\text{SSR}_{t_2}\ [\text{Jm}^{-2}] - \text{SSR}_{t_1}\ [\text{Jm}^{-2}])}{N*24*60*60}


where t2 is the 1st day of month after the month of interest, t1 is 1st day of month before t2, N is number of days in month of interest, SSRt2 is the SSR at t2, and SSRt1= is the SSR at t1.

N/A For seasonal forecasts, as data only cover 7 months
Seasonal monthly dataSSR

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

Wm-2Wm-2N/AN/AN/AN/A For seasonal forecasts, as data only cover 7 months

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