Upper boundary in SUMMA applications

[wknoben]

Asked by @kasra-keshavarz

Based on the following documentation lines:

summa/docs/input_output/SUMMA_input.md

Lines 208 to 209 in 19a7f9c

	SWRadAtm | time, hru | double | W m-2 | Downward shortwave radiation at the [upper boundary](#forcing_file_upper_boundary) | |
	LWRadAtm | time, hru | double | W m-2 | Downward longwave radiation at the [upper boundary](#forcing_file_upper_boundary) | |

summa/docs/input_output/SUMMA_input.md

Line 223 in 19a7f9c

* <a id="forcing_file_upper_boundary">Upper boundary</a>: The upper boundary refers to the upper boundary of the SUMMA domain, so this would be at some height above the canopy or ground (in case there is no canopy).

What are typical upper boundary heights defined for SUMMA applications?

If I move ahead with setting up SUMMA with Canadian ECCC RDRSv2.1 that reports radiation variables at the surface level, would the outcome be a legitimate application?

I am a little confused, so any thoughts would be greatly appreciated.

[wknoben]

I don't think there is such a thing as a typical upper boundary height. The idea of both of these variables is to get their values before any (near-)surface processes come into effect (but after things like scattering from clouds), and this seems in line with RDRS stated purpose:

The desired outputs from this system are hourly time series, available on a ∼10 km regular grid of 
the main meteorological variables that are required in order to operate surface and hydrology models: 
near-surface air temperature, near-surface air humidity, surface pressure, wind speed and direction, 
incoming infrared flux at the surface, downward solar flux at the surface, and finally precipitation.

Gasset et al., 2021 (https://hess.copernicus.org/articles/25/4917/2021/)

I expect that "at the surface" here means "at the surface (i.e. lowest) level of the atmospheric model" (and not "at the point where air and soil meet in reality"). This may be worth checking, but based on how these terms are typically used I expect it's OK to use both fluxes as model inputs as is.

[kasra-keshavarz]

Thanks for clarifying this!