Confirm correct water vapor pressure units for dvm-dos-tem input

[amullen01]

There is a potential discrepancy in the units for vapor pressure input.

Older input files (pre-2023) have vapor pressure in hPa. Input file metadata and documentation all specify that input vapor pressure should be in hPa.

Newer input files (~2023-onward) have vapor pressure in Pa, although input file metadata still says hPa.

@tobeycarman identified which functions are affected by vapor pressure:

Cohort::assignAtmEd2pfts_daily(),      -- pass thru to PFT datastructures
EnvData::atm_endOfDay(),               -- accumulate fluxes, average state...
EnvData::clear(),                      -- sets containers to zero
Soil_Env::getEvaporation(),            -- uses vpd, does calc, see getPenMonET()!!
EnvData::update_from_climate(),        -- pass thru
Cohort::updateMonthly_Env(),           -- ?? hard to say
Vegetation_Env::updateWaterBalance().  -- uses vpd and seems to expect it to be in Pa

It appears that all of the 'science' functions expect vapor pressure to be in Pa, but this could use further confirmation. This may mean that older CMTs calibrated with vapor pressure in hPa may need to be recalibrated for the new inputs. I also wonder how this affects the 'default' parameterizations for soil hydrology.

I ran my calibration for Caribou-Poker Black Spruce that was originally calibrated using Pa for vapor pressure, with vapor pressure in hPa.

• Differences in veg. carbon stocks were relatively minimal and restricted to dominant PFTs.
• Differences in Soil carbon were also minimal and mainly in humic/deepC.
• VWC was reduced significantly when using hPa. I'm assuming vapor pressure deficit was significantly higher with hPa, causing higher ET.
• Not quite sure on the effect on fluxes, will post more figures when I have time to run a proper comparison.

[amullen01]

Figures from @Benjamin-Maglio showing differences in potential evapotranspiration (PET) and liquid water content (LWCLAYER) when using Pa (VPD change) vs. hPa (Reference) as the vapor pressure unit. Run is from a bog site.