Phytoplankton temperature parameters

Question

Hi all,
I think everybody is enjoying the Christmas.
When someone back to work, please give me an advice.

At the moment I am not sure how the temperature parameters work.
We can set T_standard, T_optimum and T_maximum. And T_ref=20 is fixed.
When I set T_standard=20, T_optimum=25 and T_maximum=30.
I got the following strange function.
Is there a way to set the parameters which has maximum growth rate under 20 degC?

Cheers,

Hiroshi

 Temperature growth function for Phyto group FDIAT
 Parameters:
 a:   -686704.9    
 b:    6138.830    
 k:   2.1797977E-04
 T standard:    20.00000    
 T optimum:    25.00000    
 T maximum:    30.00000    
 T reference:    20.00000    
 Temperature, Function
   1.000000     ,  0.3305134    
   2.000000     ,  0.3503441    
   3.000000     ,  0.3713648    
   4.000000     ,  0.3936466    
   5.000000     ,  0.4172654    
   6.000000     ,  0.4423013    
   7.000000     ,  0.4688393    
   8.000000     ,  0.4969697    
   9.000000     ,  0.5267878    
   10.00000     ,  0.5583951    
   11.00000     ,  0.5918987    
   12.00000     ,  0.6274126    
   13.00000     ,  0.6650574    
   14.00000     ,  0.7049608    
   15.00000     ,  0.7472584    
   16.00000     ,  0.7920938    
   17.00000     ,  0.8396194    
   18.00000     ,  0.8899965    
   19.00000     ,  0.9433963    
   20.00000     ,   1.000000    
   21.00000     ,  0.9833984    
   22.00000     ,  0.9707031    
   23.00000     ,  0.9614258    
   24.00000     ,  0.9516602    
   25.00000     ,  0.9506836    
   26.00000     ,  0.9545898    
   27.00000     ,  0.9575195    
   28.00000     ,  0.9711914    
   29.00000     ,  0.9907227    
   30.00000     ,   1.015625    
   31.00000     ,  0.0000000E+00
   32.00000     ,  0.0000000E+00

Answer 1

Hi Hiroshi, is this the latest download?

I get

 Temperature growth function for Phyto group CHLOR
 Parameters:
 a:    25.27934    
 b:   0.1985707    
 k:    2.190974    
 T standard:    20.00000    
 T optimum:    25.00000    
 T maximum:    30.00000    
 T reference:    20.00000    
 Temperature, Function
   1.000000     ,  7.0265345E-02
   2.000000     ,  8.0805153E-02
   3.000000     ,  9.2925921E-02
   4.000000     ,  0.1068648    
   5.000000     ,  0.1228945    
   6.000000     ,  0.1413287    
   7.000000     ,  0.1625280    
   8.000000     ,  0.1869072    
   9.000000     ,  0.2149433    
   10.00000     ,  0.2471848    
   11.00000     ,  0.2842625    
   12.00000     ,  0.3269018    
   13.00000     ,  0.3759371    
   14.00000     ,  0.4323277    
   15.00000     ,  0.4971768    
   16.00000     ,  0.5717533    
   17.00000     ,  0.6575163    
   18.00000     ,  0.7561437    
   19.00000     ,  0.8695652    
   20.00000     ,   1.000000    
   21.00000     ,   1.078857    
   22.00000     ,   1.154726    
   23.00000     ,   1.221849    
   24.00000     ,   1.271705    
   25.00000     ,   1.291908    
   26.00000     ,   1.264709    
   27.00000     ,   1.164928    
   28.00000     ,  0.9571366    
   29.00000     ,  0.5917962    
   30.00000     ,  0.0000000E+00
   31.00000     ,  0.0000000E+00
   32.00000     ,  0.0000000E+00
   33.00000     ,  0.0000000E+00
   34.00000     ,  0.0000000E+00
   35.00000     ,  0.0000000E+00
   36.00000     ,  0.0000000E+00
   37.00000     ,  0.0000000E+00
   38.00000     ,  0.0000000E+00
   39.00000     ,  0.0000000E+00
   40.00000     ,  0.0000000E+00
 

Chris

Answer 2

Hi Hiroshi,

This was a strange case where the Newton method was not converging on the correct solution for the k parameter with those particular standard optimum and max parameter values.  I've put in a check for this which looks for a small k value and if found redoes the method using a different starting guess.  This seems to have fixed the issue and is in the latest download.

Also, I forgot to mention that Tref is now modifiable in the new wq model using the parameter

temperature_growth_reference.

Cheers

Chris

Comments

Hi Chris,
I got the reason.
Thank you for your quick fixing.
Regards,
Hiroshi