PRMS Solar Table Module

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Detailed Description

Presents the USGS Precipitation Runoff Modeling System (PRMS) Solar Table simulation module.


Date Taken:

Length: 00:02:29

Location Taken: Lakewood, CO, US


Steve Markstrom: OK welcome to the PRMS training
video on the Solar Table process.

In this case there is only one module for
this process.

The module is called Soltab.

And that's what I'm going to talk about here.

Basically, for each HRU, for each day of the
solar year, which is 365 days, a value of

potential or clear sky short wave solar radiation
is computed.

And then when the model runs, depending on
which day it is simulating it goes and gets

that value and knows that's the clear sky
solar radiation value for that HRU on that


This module also computes day length.

There's a couple of references there if you're
so inclined.

Alright, so if you look at the PRMS users'
manual there's a couple of equations.

Basically, what we're trying to do is get
the solar declination of each HRU on each


And you can see that equation there 1-2, which
is, yeah, a lot of trig.

Actually, no user input other than the location
and elevation and slope of the HRUs.

From the declination, you can see the declination
term here and the HRU latitude, we can compute

the sunrise and the sunset on each HRU on
each day.

Because in this case, it's symmetrical, sunrise
is the negative of sunset.

So those two are computed this way here.

Then from both of those, you can determine
the length of the day.

Then this equation here, 6-1 is used to compute
the solar table.

And you can see again, a lot of trig.

But there's the declination, the latitude
and then the day length right there.

Those plug in and we get out the solar table
for all of the HRUs.

And that's it.