Repair BioSIM's sign-dropped scientific-notation exponents
repair_fwi_exponent.RdBioSIM returns the Fire Weather Index System codes and indices as text, and drops
the minus sign from the exponent whenever a value is small enough to be formatted in
scientific notation (below 1e-4). A true 6.49936E-05 comes back as 6.49936E+05:
the mantissa is intact and only the exponent's sign is lost, so
v * 10^(-2 * floor(log10(v))) recovers the original value exactly. Verified against
the FWI System equations – FFMC = 17.1624, WS = 8.96132 gives ISI = 6.49934e-05,
and BioSIM returned 649936.
Details
Only saturated fuels drive the codes below 1e-4, so the artifact is confined to wet,
low-hazard records, but it inflates them by up to eighteen orders of magnitude. Any
downstream mean over cells or days is destroyed by a handful of contaminated records,
so this must be applied before the values are aggregated or used to derive indices.
Applied to the three moisture codes (FFMC, DMC, DC), which BioSIM reports
directly and which cannot be recomputed from the other returned columns without a
precipitation series. The behaviour indices (ISI, BUI, FWI) are pure functions of
those codes and are re-derived from the repaired values by get_fwi_daily() instead.