# How to calculate the daily average radiation

The daily average radiation is measured for the hours the sun is up. It is up for discussion to take into account the first and last hours, because these hours often don't contribute fully to the average. Similar to the hourly radiation, the radiation values from KNMI weather data column Q have to be multiplied:

${\displaystyle radiation_{daily}={\frac {\sum _{t=n}^{m}Q_{t}}{m-n+1}}\cdot 10000/3600}$,

where:

${\displaystyle n}$ is the first full hour with sun radiation.
${\displaystyle m}$ is the last full hour with sun radiation.

Column Name Unit Dutch Description
2/B YYYYMMDD Date datum (YYYY=jaar,MM=maand,DD=dag)
3/C HH Hour tijd (HH=uur, UT.12 UT=13 MET, 14 MEZT. Uurvak 05 loopt van 04.00 UT tot 5.00 UT
13/L Q J/cm2 Globale straling (in J/cm2) per uurvak;

## Notes

• The values at each hour regard the measurement over the preceding hour up to that time. To obtain the value for august 2nd, the values at 8:00 UTC of august 2nd, up to and including 7:00 UTC on august 3rd must be used.