Edward,

None of the DSSAT models use "evaporation" as an input.  It is not an option and you cannot do that.  The model uses either Priestley-Taylor or FAO-56 to generate potential ET.  You can use FAO-56 but only if you have daily wind-run and dewpoint temperature.

I'm not near my DSSAT and WEATHERMAN right now, but I don't remember what the 4.16 coefficient does.  But you have to identify SUNHR as you load it into the WEATHERMAN.

Ken Boote

________________________________________
From: DSSAT - Crop Models and Applications [[log in to unmask]] on behalf of gerardeaux [[log in to unmask]]
Sent: Friday, June 01, 2012 3:22 AM
To: [log in to unmask]
Subject: weather man

Dear DSSAT users,

I am trying to create a weather files with weatherman

I have Tmax, Tmin, SUNH , evaporation and rain from a data base in 2011.
I am importing data with weatherman and I estimate radiation from SUNH
Problem number one: when I set SUNH in hours, a multiplier by 4.16 appears,
so I have to set it to 1. It is not really a problem but I don't understand
the logic.
Reel problem is that, when I create a corrected weather file with the
radiation estimated, I have a weather file with temperatures, rainfall,
estimated radiation but not the evaporation. The data from evaporation are
in the observed weather file, not in the corrected weather file. Even when I
ask for it in the repearing setting and options.  And, when I save data into
DSSAT weather folder, I can't have a file with all my data Temperatures,
rainfall, estimated radiation and evaporation.
Please help me