Don't make too much out of this, as I don't think it affects the model function all that much.



This is likely a Joe Ritchie hold-over feature.  His old CERES-Maize code formerly had when LAI greater than 3, the fractional interception goes to 1.00, as a jump increase (which I changed about 10 years ago).  I presume wheat had the same logic.  Then when crop is at maturity, it goes to zero (as if all leaves are dead).  I think there is leaf area loss prior to maturity.



Ken Boote



-----Original Message-----

From: DSSAT - Crop Models and Applications [mailto:[log in to unmask]] On Behalf Of John Roy Porter

Sent: Wednesday, July 23, 2014 3:08 AM

To: [log in to unmask]

Subject: Re: Intercepted PAR



See



PORTER J.R., JAMIESON P.D. & WILSON D,R. (1993). Comparison of the wheat crop simulation models AFRCWHEAT2, CERES-Wheat and SWHEAT for non-limiting conditions of crop growth. Field Crops Research, 33, 131-157.



And



JAMIESON P.D., PORTER J.R., GOUDRIAAN J., RITCHIE J.T., KEULEN H. van & STOLL W. (1998). A comparison of the models AFRCWHEAT2, CERES-Wheat, Sirius, SUCROS2 and SWHEAT with measurements from wheat grown under drought. Field Crops Research, 55, 23-44.



There is a problem in CERES with respect to IPAR and RUE that does not seem to have been addressed.



Best wishes



John R Porter



Professor John R Porter DSc

Climate and Food Security, University of Copenhagen, Denmark Climate and Agriculture, Natural Resources Institute, University of Greenwich, UK



Coordinating Lead Author: IPCC AR5, Food Security and Food Production Systems Editor-in-Chief, European Journal of Agronomy



Optima scientia agricolarum semper in agro facit Amor lorem ipsum est







-----Original Message-----

From: DSSAT - Crop Models and Applications [mailto:[log in to unmask]] On Behalf Of maria soldevilla

Sent: 22. juli 2014 15:56

To: [log in to unmask]

Subject: Intercepted PAR



Dear colleagues.



I am trying to simulate the intercepted PAR (%) with the CERES-wheat model included in DSSAT. I found two issues which I dont understand, may be some of you had the same problem and can help me.

One thing is that DSSAT simulates a PAR interception of 1.00 some days of the period, which is not possible (I think the maximum should be around 0.95). On the other hand, at the end of the period the IPAR drops from 1 to

0 vertically. I guess this is because senescence is considered as a discrete event instead of as a period of progressive decrease.

I was wondering if the next DSSAT version will include any senescence routine improving this fact, or if there is anybody working on this which I could contact.

Thank you very much



Maria