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Chemistry tendency isn't equal to net IRR

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Dear All,

I'm trying to get the net O3 chemistry production and the contribution of each reaction.

The net O3 chemistry production is just the chemistry tendency variable named chem_o3 and the contributions can be calculated in the equation:
(Equation 1 in

In my opinion, dO3 should be equal to chem_o3.
So, I output the IRR and chemistry tendency with the same time step.
Here's the summary of used variables in the IRR output file:

O3 Production:

O3 Loss:
['O1D_CB4_H2O_IRR', 'OH_O3_IRR', 'HO2_O3_IRR']

Substracting Loss from Production yields the Net IRR (named Accumulated IRR in the figure).

However, if I plot the IRR and Chemistry Tendency at the same grid and level together, the values are not equal:

Note that the IRR Change and Chemistry Tendency Change are the differences by the Time dimension.
Although the trend of the accumulated values seems the same, the changes are opposite at some times.

If you have any ideas, please don't hesitate ;)