Yes, it's just what I feared. I'll try doing just that. 

On 1 August 2015 at 15:35, Solmon Fabien <fsolmon@ictp.it> wrote:

Hello James

if you do not save chemall all the fast (not transported) species are
reset to zero , the solver will recalculate a new equilibrium at every
time step .. in fact with this fix you might still generate unrealistic
concentrations for some untransported species but since you reset to zero
there are  no further consequence and the code is stable , however it does
not mean that it performs a good chemistry ... I would try to screen the
to the solver inputs just before it starts exploding, and try to play with
chemistry step dtchem.. try to reduce it from 900 s to dt maybe ..

 Fabien
> Hi everyone,
>
> I have recently tried commenting the chemall sections in the
> mod_che_chemistry.F90, as suggested by Ahmed.
>
>
>           ! 1 : initialise xrin with the concentrations from
>           !     previous chemsolv step
> !          do ic = 1 , totsp
> !            xrin(ic) = chemall(j,i,k,ic)
> !          end do
>
> and
>
>           ! save the concentrations of all species for next chemistry step
> !          do ic = 1 , totsp
> !            chemall(j,i,k,ic) = xrout(ic)
> !          end do
>           ! Store photolysis rates for diagnostic
>
> Dear Ahmed,
>
> The simulation has just run to completion this way. however, I am
> concerned
> that this way, there is no chemistry continuity between time steps. It
> this
> the case? if so, how can we resolve this?
>
> Best regards,
> James
>
>
>
> On 1 August 2015 at 12:49, <zeinab.salah@yahoo.com> wrote:
>
>> Hi James,
>>
>> We try to run the recent version also with CBMZ or DCCB and we get this
>> error also.
>> The file of regcm.in and the error message are in the attachments.
>>
>> Best regards,
>> Zeinab
>>
>>
>>
>> ------------------------------
>> *من:* James Ciarlo` <james.ciarlo@physics.org>
>> *إلى:* RegCNET <regcnet@lists.ictp.it>
>> *نسخة كربونية:* "ashalaby@ictp.it" <ashalaby@ictp.it>
>> *تاريخ الإرسال:* الثلاثاء 21 يوليو، 2015‏
>> 2:01 م
>> *الموضوع:* [RegCNET] CBMZ chemistry crash
>>
>> Dear RegCNETers,
>>
>> I have installed a recent version of the RegCM and tried to run a CBMZ
>> simulation for 1 year. However, the chemistry crashed and the simulation
>> kept on running producing a massive error log.
>>
>> After including a few lines in the mod_che_chemistry.F90 I got the
>> following information on when the error is happening:
>>
>> xrout, xrin, trac%indcbmz
>>   7.864835401599373E+153   38524086126.5782               10
>>
>> 10 is H2O2.
>>
>> I have attached the regcm.in file and the error obtained. I cannot
>> figure
>> out why this is happening. I was wondering if anyone has any idea on the
>> matter.
>>
>> Thanks and regards,
>> James
>>
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>>
>>
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--
Fabien Solmon
Research Scientist
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