Solar (shortwave) radiation flux and Sediment-Reflectivity

Question

Hi Chris

I hope you are well,

I have some questions: 

1- To implement the model, it is necessary to input four coefficients for each band (PAR, NIR, UVA, and UVB) into the run_AEM3d file. I don't understand how the model utilizes these coefficients to determine Q(z) (equation 5.3 in AEM3D_Science). Does it determine a Q(z) for each band and then sum the terms? Or does it calculate a new coefficient that takes into account the four previous ones?

2. Is there an output available through which I can obtain the values of Q(z) (eq. 5.3) and Qsw (eq. 5.1)?

3. What is it and in what equation does AEM3D use sediment-reflectivity?

Thanks!

Laura

Answer 1

Hi Laura,

Solar_rad is broken up into the four components using the ratios

SW_FRAC_PAR = 0.45  

SW_FRAC_NIR = 0.51  

SW_FRAC_UVA = 0.035

SW_FRAC_UVB = 0.005

These default values can be overwritten in run_aem3d using the keys above.

If the water quality module is used then the four components are stored each timestep and can be output using the datablock keywords PAR, NIR, UVA, and UVB. If water quality is not turned on then the values are not stored.

If any short wave radiation is left when the for loop gets to the bottom then a fraction of this is reflected upwards.  This fraction is defined using the sediment_reflectivity.  The reflected radiation is the sum of all 4 groups and uses the extinction coefficient default_rflct_extinction