Hi stavridou,

There are different ways of conversion of these units, for example, u can use this: PAR (umol m-2 s-1 ) / 4.6 = W m-2.

"Following E=hc/λ, the conversion factor is wavelength-dependent and averaged for λ=400-700 (PAR) is ~ 4.6"

W m-2 X 0.0864 = MJ m-2 day-1. or u can use the following link to get easy ways, https://www.purdue.edu/hla/sites/cea/wp-content/uploads/sites/15/2016/12/Light-Quantity-and-Quality.pdf

from the page 4 of document attached you can find the conversion from umol m-2 s-1 to MJ m-2d-1, and other.

Dear Eleftheria Stavridou

Watt is a unit of power and is defined as a derived unit of 1 joule per second. Let the instantaneous solar radiation is equal to 1000 W/m2. If this quantity is received for one hour period by a surface, the total energy collected in MJ/m2 becomes equal to (1000 W/m2)x(3600 second)/(1 MJ/J) = 3.6 MJ/m2.

I think this link might be helpful further, have a look:

https://stackoverflow.com/questions/40826466/solar-energy-conversion-w-m2-to-mj-m2

Best Regards

Qamar Ul Islam

Thank you for the replies I guess I would be using the average of the 30 min values to get the daily PAR, right?