|PRECIS support forum
|evapotranspiration in PRECIS
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|Author:||rahele [ Sun May 25, 2014 6:01 am ]|
|Post subject:||evapotranspiration in PRECIS|
I would study on evapotranspiration on my country (Iran),
I have a few questions:
1- Which STASH codes can I use for evaporate?
2- How units of Evaporation (kg/m2/s) to mm / day have become?
I run Precis Model for 2070-2100, Evaporation data for this time is 1500 to 15000 mm/day,
for The study area is too high!!!!!!
Thanks a lot
|Author:||dmhg [ Mon May 26, 2014 2:31 pm ]|
|Post subject:||Re: evapotranspiration in PRECIS|
I have found the following guidance from an old email
To calculate the evaporation from the soil, vegetation (via evaporation of water on the vegetation) and vegetation (via transpiration) you need STASH items 3296, 3297 and 3299 and to complete the full set of surface moisture fluxes we have a sublimation diagnostic, 3298.
3296 EVAPORATION RATE FROM SOIL SURFACE kg m−2s−1 Mean Single
3297 EVAPORATION RATE FROM CANOPY kg m−2s−1 Mean Single
3298 SUBLIMATION RATE AT SURFACE kg m−2s−1 Mean Single
3299 TRANSPIRATION kg m−2s−1 Mean Single
Alternatively, the total surface moisture flux is given by stash item 3223 at the surface.
3223 SURFACE & BL MOISTURE FLUXES kg m−2s−1 Mean MLB 5
3223 is defined throughout the boundary layer with the lowest level being the surface moisture flux.
Finally, 3312 is the potential evaporation rate of open water.
Does this help answer your first question?
To convert a file with units km/m2/sec (equivalent to millimetres per second), you need to multiply the values in the file by 86400 (the number of seconds in one day).
For example, let's say I have a file dmhaea.pat2aug.05216.pp which is runid dmhae, a.pa (Daily means), t2 (2092), aug (August), 05216 (Stash code for Total Precipitation Rate) and a pp file.
I can convert this file using the PRECIS analysis tool called ppexpr
ppexpr -x "a*86400" -o newfile.pp a=dmhaea.pat2aug.05216.pp
The output file newfile.pp will contain values in millimetres per day rather than SI unit millimetres per second.
If you want to convert all the daily mean files in one directory, use a Unix regular expression. e.g.
ppexpr -x "a*86400" -e $HOME/OUTPUT a=*a.pa*.pp
That will convert all daily mean files *a.pa*.pp to daily means in mm/day, outputting the new files to $HOME/OUTPUT
Hope this helps
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