Error in TWOSTREAM subroutine (module_sf_noahmplsm.F)

Hi everyone,

I am running WRF4.2.2 at urban scale (1km) after having successfully completed the simulations for the parent domains D01 and D02 (15km and 5km).

Unfortunately, in one of my urban domain I get a segmentation fault after 6 hours from the beginning of the simulation. Playing with debugging options I found that the error originates in the TWOSTREAM soubroutine, where I have a divided by 0 at this line:

D1 = P1*TMP2/S1 – P2*TMP3*S1​

As in the above equation the only denominator is S1 ( S1 = EXP(-H*VAI) ), I printed the values of the variables used to compute S1 finding that for some reasons the VAI (one-sided leaf+stem area index) becomes too large in one or more points:

H, VAI, S1 = 0.8423577, 108.3101, 0.0000000E+00​

As cross check, I prescribed S1 to a fix value when it is null and I have been able to overcome the issue and complete the simulation. Besides, I reviewed the namelist and I found out that the error occurs only when I use the dynamic vegetation option within Noah-MP. Interestingly, the same simulation (same namelist) is running correctly on a different urban domain.
As this issue does not originate into the TWOSTREAM subroutine, but where the VAI variable is computed, I was wondering whether I can prescribe VAI when it is larger than a given value? If so, which is the range of variability of VAI? Anyway, other solutions to find the bug and fix this error are welcome.

Thanks into advance for support,



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